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Auto merge of #63469 - Centril:refactor-parser, r=petrochenkov

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libsyntax: Refactor `parser.rs` into reasonably sized logical units

Here we split `parser.rs` (~7.9 KLOC) into more reasonably sized files (all < 1.8 KLOC):

- `./src/libsyntax/parse/`
   - `parser.rs`
   - `parser/`
      - `pat.rs`
      - `expr.rs`
      - `stmt.rs`
      - `ty.rs`
      - `path.rs`
      - `generics.rs`
      - `item.rs`
      - `module.rs`

Closes https://github.com/rust-lang/rust/issues/60015.

r? @petrochenkov
This commit is contained in:
bors 2019-08-12 02:35:55 +00:00
commit 72f8043d44
9 changed files with 6324 additions and 6191 deletions
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6217
src/libsyntax/parse/parser.rs
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src/libsyntax/parse/parser/generics.rs Normal file
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use super::{Parser, PResult};
use crate::ast::{self, WhereClause, GenericParam, GenericParamKind, GenericBounds, Attribute};
use crate::parse::token;
use crate::source_map::DUMMY_SP;
use crate::symbol::kw;
impl<'a> Parser<'a> {
/// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
///
/// ```
/// BOUND = LT_BOUND (e.g., `'a`)
/// ```
fn parse_lt_param_bounds(&mut self) -> GenericBounds {
let mut lifetimes = Vec::new();
while self.check_lifetime() {
lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
if !self.eat_plus() {
break
}
}
lifetimes
}
/// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
fn parse_ty_param(&mut self,
preceding_attrs: Vec<Attribute>)
-> PResult<'a, GenericParam> {
let ident = self.parse_ident()?;
// Parse optional colon and param bounds.
let bounds = if self.eat(&token::Colon) {
self.parse_generic_bounds(Some(self.prev_span))?
} else {
Vec::new()
};
let default = if self.eat(&token::Eq) {
Some(self.parse_ty()?)
} else {
None
};
Ok(GenericParam {
ident,
id: ast::DUMMY_NODE_ID,
attrs: preceding_attrs.into(),
bounds,
kind: GenericParamKind::Type {
default,
}
})
}
fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
self.expect_keyword(kw::Const)?;
let ident = self.parse_ident()?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
Ok(GenericParam {
ident,
id: ast::DUMMY_NODE_ID,
attrs: preceding_attrs.into(),
bounds: Vec::new(),
kind: GenericParamKind::Const {
ty,
}
})
}
/// Parses a (possibly empty) list of lifetime and type parameters, possibly including
/// a trailing comma and erroneous trailing attributes.
crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
let mut params = Vec::new();
loop {
let attrs = self.parse_outer_attributes()?;
if self.check_lifetime() {
let lifetime = self.expect_lifetime();
// Parse lifetime parameter.
let bounds = if self.eat(&token::Colon) {
self.parse_lt_param_bounds()
} else {
Vec::new()
};
params.push(ast::GenericParam {
ident: lifetime.ident,
id: lifetime.id,
attrs: attrs.into(),
bounds,
kind: ast::GenericParamKind::Lifetime,
});
} else if self.check_keyword(kw::Const) {
// Parse const parameter.
params.push(self.parse_const_param(attrs)?);
} else if self.check_ident() {
// Parse type parameter.
params.push(self.parse_ty_param(attrs)?);
} else {
// Check for trailing attributes and stop parsing.
if !attrs.is_empty() {
if !params.is_empty() {
self.struct_span_err(
attrs[0].span,
&format!("trailing attribute after generic parameter"),
)
.span_label(attrs[0].span, "attributes must go before parameters")
.emit();
} else {
self.struct_span_err(
attrs[0].span,
&format!("attribute without generic parameters"),
)
.span_label(
attrs[0].span,
"attributes are only permitted when preceding parameters",
)
.emit();
}
}
break
}
if !self.eat(&token::Comma) {
break
}
}
Ok(params)
}
/// Parses a set of optional generic type parameter declarations. Where
/// clauses are not parsed here, and must be added later via
/// `parse_where_clause()`.
///
/// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
/// | ( < lifetimes , typaramseq ( , )? > )
/// where typaramseq = ( typaram ) | ( typaram , typaramseq )
pub(super) fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
let span_lo = self.token.span;
let (params, span) = if self.eat_lt() {
let params = self.parse_generic_params()?;
self.expect_gt()?;
(params, span_lo.to(self.prev_span))
} else {
(vec![], self.prev_span.between(self.token.span))
};
Ok(ast::Generics {
params,
where_clause: WhereClause {
predicates: Vec::new(),
span: DUMMY_SP,
},
span,
})
}
/// Parses an optional where-clause and places it in `generics`.
///
/// ```ignore (only-for-syntax-highlight)
/// where T : Trait<U, V> + 'b, 'a : 'b
/// ```
pub(super) fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
let mut where_clause = WhereClause {
predicates: Vec::new(),
span: self.prev_span.to(self.prev_span),
};
if !self.eat_keyword(kw::Where) {
return Ok(where_clause);
}
let lo = self.prev_span;
// We are considering adding generics to the `where` keyword as an alternative higher-rank
// parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
// change we parse those generics now, but report an error.
if self.choose_generics_over_qpath() {
let generics = self.parse_generics()?;
self.struct_span_err(
generics.span,
"generic parameters on `where` clauses are reserved for future use",
)
.span_label(generics.span, "currently unsupported")
.emit();
}
loop {
let lo = self.token.span;
if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
let lifetime = self.expect_lifetime();
// Bounds starting with a colon are mandatory, but possibly empty.
self.expect(&token::Colon)?;
let bounds = self.parse_lt_param_bounds();
where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
ast::WhereRegionPredicate {
span: lo.to(self.prev_span),
lifetime,
bounds,
}
));
} else if self.check_type() {
// Parse optional `for<'a, 'b>`.
// This `for` is parsed greedily and applies to the whole predicate,
// the bounded type can have its own `for` applying only to it.
// Examples:
// * `for<'a> Trait1<'a>: Trait2<'a /* ok */>`
// * `(for<'a> Trait1<'a>): Trait2<'a /* not ok */>`
// * `for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /* ok */, 'b /* not ok */>`
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
// Parse type with mandatory colon and (possibly empty) bounds,
// or with mandatory equality sign and the second type.
let ty = self.parse_ty()?;
if self.eat(&token::Colon) {
let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
ast::WhereBoundPredicate {
span: lo.to(self.prev_span),
bound_generic_params: lifetime_defs,
bounded_ty: ty,
bounds,
}
));
// FIXME: Decide what should be used here, `=` or `==`.
// FIXME: We are just dropping the binders in lifetime_defs on the floor here.
} else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
let rhs_ty = self.parse_ty()?;
where_clause.predicates.push(ast::WherePredicate::EqPredicate(
ast::WhereEqPredicate {
span: lo.to(self.prev_span),
lhs_ty: ty,
rhs_ty,
id: ast::DUMMY_NODE_ID,
}
));
} else {
return self.unexpected();
}
} else {
break
}
if !self.eat(&token::Comma) {
break
}
}
where_clause.span = lo.to(self.prev_span);
Ok(where_clause)
}
pub(super) fn choose_generics_over_qpath(&self) -> bool {
// There's an ambiguity between generic parameters and qualified paths in impls.
// If we see `<` it may start both, so we have to inspect some following tokens.
// The following combinations can only start generics,
// but not qualified paths (with one exception):
// `<` `>` - empty generic parameters
// `<` `#` - generic parameters with attributes
// `<` (LIFETIME|IDENT) `>` - single generic parameter
// `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
// `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
// `<` (LIFETIME|IDENT) `=` - generic parameter with a default
// `<` const - generic const parameter
// The only truly ambiguous case is
// `<` IDENT `>` `::` IDENT ...
// we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
// because this is what almost always expected in practice, qualified paths in impls
// (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
self.token == token::Lt &&
(self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
t == &token::Colon || t == &token::Eq) ||
self.is_keyword_ahead(1, &[kw::Const]))
}
}

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use super::{Parser, PResult};
use super::item::ItemInfo;
use crate::attr;
use crate::ast::{self, Ident, Attribute, ItemKind, Mod, Crate};
use crate::parse::{new_sub_parser_from_file, DirectoryOwnership};
use crate::parse::token::{self, TokenKind};
use crate::parse::diagnostics::{Error};
use crate::source_map::{SourceMap, Span, DUMMY_SP, FileName};
use crate::symbol::sym;
use std::path::{self, Path, PathBuf};
/// Information about the path to a module.
pub struct ModulePath {
name: String,
path_exists: bool,
pub result: Result<ModulePathSuccess, Error>,
}
pub struct ModulePathSuccess {
pub path: PathBuf,
pub directory_ownership: DirectoryOwnership,
warn: bool,
}
impl<'a> Parser<'a> {
/// Parses a source module as a crate. This is the main entry point for the parser.
pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
let lo = self.token.span;
let krate = Ok(ast::Crate {
attrs: self.parse_inner_attributes()?,
module: self.parse_mod_items(&token::Eof, lo)?,
span: lo.to(self.token.span),
});
krate
}
/// Parse a `mod <foo> { ... }` or `mod <foo>;` item
pub(super) fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
let (in_cfg, outer_attrs) = {
let mut strip_unconfigured = crate::config::StripUnconfigured {
sess: self.sess,
features: None, // don't perform gated feature checking
};
let mut outer_attrs = outer_attrs.to_owned();
strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
(!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
};
let id_span = self.token.span;
let id = self.parse_ident()?;
if self.eat(&token::Semi) {
if in_cfg && self.recurse_into_file_modules {
// This mod is in an external file. Let's go get it!
let ModulePathSuccess { path, directory_ownership, warn } =
self.submod_path(id, &outer_attrs, id_span)?;
let (module, mut attrs) =
self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
// Record that we fetched the mod from an external file
if warn {
let attr = attr::mk_attr_outer(
attr::mk_word_item(Ident::with_empty_ctxt(sym::warn_directory_ownership)));
attr::mark_known(&attr);
attrs.push(attr);
}
Ok((id, ItemKind::Mod(module), Some(attrs)))
} else {
let placeholder = ast::Mod {
inner: DUMMY_SP,
items: Vec::new(),
inline: false
};
Ok((id, ItemKind::Mod(placeholder), None))
}
} else {
let old_directory = self.directory.clone();
self.push_directory(id, &outer_attrs);
self.expect(&token::OpenDelim(token::Brace))?;
let mod_inner_lo = self.token.span;
let attrs = self.parse_inner_attributes()?;
let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
self.directory = old_directory;
Ok((id, ItemKind::Mod(module), Some(attrs)))
}
}
/// Given a termination token, parses all of the items in a module.
fn parse_mod_items(&mut self, term: &TokenKind, inner_lo: Span) -> PResult<'a, Mod> {
let mut items = vec![];
while let Some(item) = self.parse_item()? {
items.push(item);
self.maybe_consume_incorrect_semicolon(&items);
}
if !self.eat(term) {
let token_str = self.this_token_descr();
if !self.maybe_consume_incorrect_semicolon(&items) {
let mut err = self.fatal(&format!("expected item, found {}", token_str));
err.span_label(self.token.span, "expected item");
return Err(err);
}
}
let hi = if self.token.span.is_dummy() {
inner_lo
} else {
self.prev_span
};
Ok(Mod {
inner: inner_lo.to(hi),
items,
inline: true
})
}
fn submod_path(
&mut self,
id: ast::Ident,
outer_attrs: &[Attribute],
id_sp: Span
) -> PResult<'a, ModulePathSuccess> {
if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
return Ok(ModulePathSuccess {
directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
// All `#[path]` files are treated as though they are a `mod.rs` file.
// This means that `mod foo;` declarations inside `#[path]`-included
// files are siblings,
//
// Note that this will produce weirdness when a file named `foo.rs` is
// `#[path]` included and contains a `mod foo;` declaration.
// If you encounter this, it's your own darn fault :P
Some(_) => DirectoryOwnership::Owned { relative: None },
_ => DirectoryOwnership::UnownedViaMod(true),
},
path,
warn: false,
});
}
let relative = match self.directory.ownership {
DirectoryOwnership::Owned { relative } => relative,
DirectoryOwnership::UnownedViaBlock |
DirectoryOwnership::UnownedViaMod(_) => None,
};
let paths = Parser::default_submod_path(
id, relative, &self.directory.path, self.sess.source_map());
match self.directory.ownership {
DirectoryOwnership::Owned { .. } => {
paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
},
DirectoryOwnership::UnownedViaBlock => {
let msg =
"Cannot declare a non-inline module inside a block \
unless it has a path attribute";
let mut err = self.diagnostic().struct_span_err(id_sp, msg);
if paths.path_exists {
let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
paths.name);
err.span_note(id_sp, &msg);
}
Err(err)
}
DirectoryOwnership::UnownedViaMod(warn) => {
if warn {
if let Ok(result) = paths.result {
return Ok(ModulePathSuccess { warn: true, ..result });
}
}
let mut err = self.diagnostic().struct_span_err(id_sp,
"cannot declare a new module at this location");
if !id_sp.is_dummy() {
let src_path = self.sess.source_map().span_to_filename(id_sp);
if let FileName::Real(src_path) = src_path {
if let Some(stem) = src_path.file_stem() {
let mut dest_path = src_path.clone();
dest_path.set_file_name(stem);
dest_path.push("mod.rs");
err.span_note(id_sp,
&format!("maybe move this module `{}` to its own \
directory via `{}`", src_path.display(),
dest_path.display()));
}
}
}
if paths.path_exists {
err.span_note(id_sp,
&format!("... or maybe `use` the module `{}` instead \
of possibly redeclaring it",
paths.name));
}
Err(err)
}
}
}
pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
let s = s.as_str();
// On windows, the base path might have the form
// `\\?\foo\bar` in which case it does not tolerate
// mixed `/` and `\` separators, so canonicalize
// `/` to `\`.
#[cfg(windows)]
let s = s.replace("/", "\\");
Some(dir_path.join(s))
} else {
None
}
}
/// Returns a path to a module.
pub fn default_submod_path(
id: ast::Ident,
relative: Option<ast::Ident>,
dir_path: &Path,
source_map: &SourceMap) -> ModulePath
{
// If we're in a foo.rs file instead of a mod.rs file,
// we need to look for submodules in
// `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
// `./<id>.rs` and `./<id>/mod.rs`.
let relative_prefix_string;
let relative_prefix = if let Some(ident) = relative {
relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
&relative_prefix_string
} else {
""
};
let mod_name = id.to_string();
let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
let secondary_path_str = format!("{}{}{}mod.rs",
relative_prefix, mod_name, path::MAIN_SEPARATOR);
let default_path = dir_path.join(&default_path_str);
let secondary_path = dir_path.join(&secondary_path_str);
let default_exists = source_map.file_exists(&default_path);
let secondary_exists = source_map.file_exists(&secondary_path);
let result = match (default_exists, secondary_exists) {
(true, false) => Ok(ModulePathSuccess {
path: default_path,
directory_ownership: DirectoryOwnership::Owned {
relative: Some(id),
},
warn: false,
}),
(false, true) => Ok(ModulePathSuccess {
path: secondary_path,
directory_ownership: DirectoryOwnership::Owned {
relative: None,
},
warn: false,
}),
(false, false) => Err(Error::FileNotFoundForModule {
mod_name: mod_name.clone(),
default_path: default_path_str,
secondary_path: secondary_path_str,
dir_path: dir_path.display().to_string(),
}),
(true, true) => Err(Error::DuplicatePaths {
mod_name: mod_name.clone(),
default_path: default_path_str,
secondary_path: secondary_path_str,
}),
};
ModulePath {
name: mod_name,
path_exists: default_exists || secondary_exists,
result,
}
}
/// Reads a module from a source file.
fn eval_src_mod(
&mut self,
path: PathBuf,
directory_ownership: DirectoryOwnership,
name: String,
id_sp: Span,
) -> PResult<'a, (Mod, Vec<Attribute>)> {
let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
let mut err = String::from("circular modules: ");
let len = included_mod_stack.len();
for p in &included_mod_stack[i.. len] {
err.push_str(&p.to_string_lossy());
err.push_str(" -> ");
}
err.push_str(&path.to_string_lossy());
return Err(self.span_fatal(id_sp, &err[..]));
}
included_mod_stack.push(path.clone());
drop(included_mod_stack);
let mut p0 =
new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
p0.cfg_mods = self.cfg_mods;
let mod_inner_lo = p0.token.span;
let mod_attrs = p0.parse_inner_attributes()?;
let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
m0.inline = false;
self.sess.included_mod_stack.borrow_mut().pop();
Ok((m0, mod_attrs))
}
fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
self.directory.path.to_mut().push(&path.as_str());
self.directory.ownership = DirectoryOwnership::Owned { relative: None };
} else {
// We have to push on the current module name in the case of relative
// paths in order to ensure that any additional module paths from inline
// `mod x { ... }` come after the relative extension.
//
// For example, a `mod z { ... }` inside `x/y.rs` should set the current
// directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
if let Some(ident) = relative.take() { // remove the relative offset
self.directory.path.to_mut().push(ident.as_str());
}
}
self.directory.path.to_mut().push(&id.as_str());
}
}
}

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use super::{Parser, PResult, PathStyle};
use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
use crate::ptr::P;
use crate::ast::{self, Attribute, Pat, PatKind, FieldPat, RangeEnd, RangeSyntax, Mac_};
use crate::ast::{BindingMode, Ident, Mutability, Expr, ExprKind};
use crate::parse::token::{self};
use crate::print::pprust;
use crate::source_map::{respan, Span, Spanned};
use crate::symbol::kw;
use crate::ThinVec;
use errors::{Applicability, DiagnosticBuilder};
impl<'a> Parser<'a> {
/// Parses a pattern.
pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
self.parse_pat_with_range_pat(true, expected)
}
/// Parses patterns, separated by '|' s.
pub(super) fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
// Allow a '|' before the pats (RFC 1925 + RFC 2530)
self.eat(&token::BinOp(token::Or));
let mut pats = Vec::new();
loop {
pats.push(self.parse_top_level_pat()?);
if self.token == token::OrOr {
self.struct_span_err(self.token.span, "unexpected token `||` after pattern")
.span_suggestion(
self.token.span,
"use a single `|` to specify multiple patterns",
"|".to_owned(),
Applicability::MachineApplicable
)
.emit();
self.bump();
} else if self.eat(&token::BinOp(token::Or)) {
// This is a No-op. Continue the loop to parse the next
// pattern.
} else {
return Ok(pats);
}
};
}
/// A wrapper around `parse_pat` with some special error handling for the
/// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
/// to subpatterns within such).
pub(super) fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
let pat = self.parse_pat(None)?;
if self.token == token::Comma {
// An unexpected comma after a top-level pattern is a clue that the
// user (perhaps more accustomed to some other language) forgot the
// parentheses in what should have been a tuple pattern; return a
// suggestion-enhanced error here rather than choking on the comma
// later.
let comma_span = self.token.span;
self.bump();
if let Err(mut err) = self.skip_pat_list() {
// We didn't expect this to work anyway; we just wanted
// to advance to the end of the comma-sequence so we know
// the span to suggest parenthesizing
err.cancel();
}
let seq_span = pat.span.to(self.prev_span);
let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
err.span_suggestion(
seq_span,
"try adding parentheses to match on a tuple..",
format!("({})", seq_snippet),
Applicability::MachineApplicable
).span_suggestion(
seq_span,
"..or a vertical bar to match on multiple alternatives",
format!("{}", seq_snippet.replace(",", " |")),
Applicability::MachineApplicable
);
}
return Err(err);
}
Ok(pat)
}
/// Parse and throw away a parentesized comma separated
/// sequence of patterns until `)` is reached.
fn skip_pat_list(&mut self) -> PResult<'a, ()> {
while !self.check(&token::CloseDelim(token::Paren)) {
self.parse_pat(None)?;
if !self.eat(&token::Comma) {
return Ok(())
}
}
Ok(())
}
/// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
/// allowed).
fn parse_pat_with_range_pat(
&mut self,
allow_range_pat: bool,
expected: Option<&'static str>,
) -> PResult<'a, P<Pat>> {
maybe_recover_from_interpolated_ty_qpath!(self, true);
maybe_whole!(self, NtPat, |x| x);
let lo = self.token.span;
let pat;
match self.token.kind {
token::BinOp(token::And) | token::AndAnd => {
// Parse &pat / &mut pat
self.expect_and()?;
let mutbl = self.parse_mutability();
if let token::Lifetime(name) = self.token.kind {
let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern", name));
err.span_label(self.token.span, "unexpected lifetime");
return Err(err);
}
let subpat = self.parse_pat_with_range_pat(false, expected)?;
pat = PatKind::Ref(subpat, mutbl);
}
token::OpenDelim(token::Paren) => {
// Parse a tuple or parenthesis pattern.
let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| p.parse_pat(None))?;
// Here, `(pat,)` is a tuple pattern.
// For backward compatibility, `(..)` is a tuple pattern as well.
pat = if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) {
PatKind::Paren(fields.into_iter().nth(0).unwrap())
} else {
PatKind::Tuple(fields)
};
}
token::OpenDelim(token::Bracket) => {
// Parse `[pat, pat,...]` as a slice pattern.
let (slice, _) = self.parse_delim_comma_seq(token::Bracket, |p| p.parse_pat(None))?;
pat = PatKind::Slice(slice);
}
token::DotDot => {
self.bump();
pat = if self.is_pat_range_end_start() {
// Parse `..42` for recovery.
self.parse_pat_range_to(RangeEnd::Excluded, "..")?
} else {
// A rest pattern `..`.
PatKind::Rest
};
}
token::DotDotEq => {
// Parse `..=42` for recovery.
self.bump();
pat = self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotEq), "..=")?;
}
token::DotDotDot => {
// Parse `...42` for recovery.
self.bump();
pat = self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotDot), "...")?;
}
// At this point, token != &, &&, (, [
_ => if self.eat_keyword(kw::Underscore) {
// Parse _
pat = PatKind::Wild;
} else if self.eat_keyword(kw::Mut) {
// Parse mut ident @ pat / mut ref ident @ pat
let mutref_span = self.prev_span.to(self.token.span);
let binding_mode = if self.eat_keyword(kw::Ref) {
self.diagnostic()
.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
.span_suggestion(
mutref_span,
"try switching the order",
"ref mut".into(),
Applicability::MachineApplicable
).emit();
BindingMode::ByRef(Mutability::Mutable)
} else {
BindingMode::ByValue(Mutability::Mutable)
};
pat = self.parse_pat_ident(binding_mode)?;
} else if self.eat_keyword(kw::Ref) {
// Parse ref ident @ pat / ref mut ident @ pat
let mutbl = self.parse_mutability();
pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
} else if self.eat_keyword(kw::Box) {
// Parse box pat
let subpat = self.parse_pat_with_range_pat(false, None)?;
pat = PatKind::Box(subpat);
} else if self.token.is_ident() && !self.token.is_reserved_ident() &&
self.parse_as_ident() {
// Parse ident @ pat
// This can give false positives and parse nullary enums,
// they are dealt with later in resolve
let binding_mode = BindingMode::ByValue(Mutability::Immutable);
pat = self.parse_pat_ident(binding_mode)?;
} else if self.token.is_path_start() {
// Parse pattern starting with a path
let (qself, path) = if self.eat_lt() {
// Parse a qualified path
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Expr)?)
};
match self.token.kind {
token::Not if qself.is_none() => {
// Parse macro invocation
self.bump();
let (delim, tts) = self.expect_delimited_token_tree()?;
let mac = respan(lo.to(self.prev_span), Mac_ {
path,
tts,
delim,
prior_type_ascription: self.last_type_ascription,
});
pat = PatKind::Mac(mac);
}
token::DotDotDot | token::DotDotEq | token::DotDot => {
let (end_kind, form) = match self.token.kind {
token::DotDot => (RangeEnd::Excluded, ".."),
token::DotDotDot => (RangeEnd::Included(RangeSyntax::DotDotDot), "..."),
token::DotDotEq => (RangeEnd::Included(RangeSyntax::DotDotEq), "..="),
_ => panic!("can only parse `..`/`...`/`..=` for ranges \
(checked above)"),
};
let op_span = self.token.span;
// Parse range
let span = lo.to(self.prev_span);
let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
self.bump();
let end = self.parse_pat_range_end_opt(&begin, form)?;
pat = PatKind::Range(begin, end, respan(op_span, end_kind));
}
token::OpenDelim(token::Brace) => {
if qself.is_some() {
let msg = "unexpected `{` after qualified path";
let mut err = self.fatal(msg);
err.span_label(self.token.span, msg);
return Err(err);
}
// Parse struct pattern
self.bump();
let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
e.emit();
self.recover_stmt();
(vec![], true)
});
self.bump();
pat = PatKind::Struct(path, fields, etc);
}
token::OpenDelim(token::Paren) => {
if qself.is_some() {
let msg = "unexpected `(` after qualified path";
let mut err = self.fatal(msg);
err.span_label(self.token.span, msg);
return Err(err);
}
// Parse tuple struct or enum pattern
let (fields, _) = self.parse_paren_comma_seq(|p| p.parse_pat(None))?;
pat = PatKind::TupleStruct(path, fields)
}
_ => pat = PatKind::Path(qself, path),
}
} else {
// Try to parse everything else as literal with optional minus
match self.parse_literal_maybe_minus() {
Ok(begin) => {
let op_span = self.token.span;
if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
self.check(&token::DotDotDot) {
let (end_kind, form) = if self.eat(&token::DotDotDot) {
(RangeEnd::Included(RangeSyntax::DotDotDot), "...")
} else if self.eat(&token::DotDotEq) {
(RangeEnd::Included(RangeSyntax::DotDotEq), "..=")
} else if self.eat(&token::DotDot) {
(RangeEnd::Excluded, "..")
} else {
panic!("impossible case: we already matched \
on a range-operator token")
};
let end = self.parse_pat_range_end_opt(&begin, form)?;
pat = PatKind::Range(begin, end, respan(op_span, end_kind))
} else {
pat = PatKind::Lit(begin);
}
}
Err(mut err) => {
self.cancel(&mut err);
let expected = expected.unwrap_or("pattern");
let msg = format!(
"expected {}, found {}",
expected,
self.this_token_descr(),
);
let mut err = self.fatal(&msg);
err.span_label(self.token.span, format!("expected {}", expected));
let sp = self.sess.source_map().start_point(self.token.span);
if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
self.sess.expr_parentheses_needed(&mut err, *sp, None);
}
return Err(err);
}
}
}
}
let pat = self.mk_pat(lo.to(self.prev_span), pat);
let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
if !allow_range_pat {
match pat.node {
PatKind::Range(
_, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
) => {},
PatKind::Range(..) => {
let mut err = self.struct_span_err(
pat.span,
"the range pattern here has ambiguous interpretation",
);
err.span_suggestion(
pat.span,
"add parentheses to clarify the precedence",
format!("({})", pprust::pat_to_string(&pat)),
// "ambiguous interpretation" implies that we have to be guessing
Applicability::MaybeIncorrect
);
return Err(err);
}
_ => {}
}
}
Ok(pat)
}
// Helper function to decide whether to parse as ident binding
// or to try to do something more complex like range patterns.
fn parse_as_ident(&mut self) -> bool {
self.look_ahead(1, |t| match t.kind {
token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
token::DotDotDot | token::DotDotEq | token::DotDot |
token::ModSep | token::Not => false,
_ => true,
})
}
/// Is the current token suitable as the start of a range patterns end?
fn is_pat_range_end_start(&self) -> bool {
self.token.is_path_start() // e.g. `MY_CONST`;
|| self.token == token::Dot // e.g. `.5` for recovery;
|| self.token.can_begin_literal_or_bool() // e.g. `42`.
|| self.token.is_whole_expr()
}
/// Parse a range-to pattern, e.g. `..X` and `..=X` for recovery.
fn parse_pat_range_to(&mut self, re: RangeEnd, form: &str) -> PResult<'a, PatKind> {
let lo = self.prev_span;
let end = self.parse_pat_range_end()?;
let range_span = lo.to(end.span);
let begin = self.mk_expr(range_span, ExprKind::Err, ThinVec::new());
self.diagnostic()
.struct_span_err(range_span, &format!("`{}X` range patterns are not supported", form))
.span_suggestion(
range_span,
"try using the minimum value for the type",
format!("MIN{}{}", form, pprust::expr_to_string(&end)),
Applicability::HasPlaceholders,
)
.emit();
Ok(PatKind::Range(begin, end, respan(lo, re)))
}
/// Parse the end of a `X..Y`, `X..=Y`, or `X...Y` range pattern or recover
/// if that end is missing treating it as `X..`, `X..=`, or `X...` respectively.
fn parse_pat_range_end_opt(&mut self, begin: &Expr, form: &str) -> PResult<'a, P<Expr>> {
if self.is_pat_range_end_start() {
// Parsing e.g. `X..=Y`.
self.parse_pat_range_end()
} else {
// Parsing e.g. `X..`.
let range_span = begin.span.to(self.prev_span);
self.diagnostic()
.struct_span_err(
range_span,
&format!("`X{}` range patterns are not supported", form),
)
.span_suggestion(
range_span,
"try using the maximum value for the type",
format!("{}{}MAX", pprust::expr_to_string(&begin), form),
Applicability::HasPlaceholders,
)
.emit();
Ok(self.mk_expr(range_span, ExprKind::Err, ThinVec::new()))
}
}
fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
if self.token.is_path_start() {
let lo = self.token.span;
let (qself, path) = if self.eat_lt() {
// Parse a qualified path
let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
(Some(qself), path)
} else {
// Parse an unqualified path
(None, self.parse_path(PathStyle::Expr)?)
};
let hi = self.prev_span;
Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
} else {
self.parse_literal_maybe_minus()
}
}
/// Parses `ident` or `ident @ pat`.
/// used by the copy foo and ref foo patterns to give a good
/// error message when parsing mistakes like `ref foo(a, b)`.
fn parse_pat_ident(&mut self,
binding_mode: ast::BindingMode)
-> PResult<'a, PatKind> {
let ident = self.parse_ident()?;
let sub = if self.eat(&token::At) {
Some(self.parse_pat(Some("binding pattern"))?)
} else {
None
};
// just to be friendly, if they write something like
// ref Some(i)
// we end up here with ( as the current token. This shortly
// leads to a parse error. Note that if there is no explicit
// binding mode then we do not end up here, because the lookahead
// will direct us over to parse_enum_variant()
if self.token == token::OpenDelim(token::Paren) {
return Err(self.span_fatal(
self.prev_span,
"expected identifier, found enum pattern"))
}
Ok(PatKind::Ident(binding_mode, ident, sub))
}
/// Parses the fields of a struct-like pattern.
fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<Spanned<FieldPat>>, bool)> {
let mut fields = Vec::new();
let mut etc = false;
let mut ate_comma = true;
let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
let mut etc_span = None;
while self.token != token::CloseDelim(token::Brace) {
let attrs = match self.parse_outer_attributes() {
Ok(attrs) => attrs,
Err(err) => {
if let Some(mut delayed) = delayed_err {
delayed.emit();
}
return Err(err);
},
};
let lo = self.token.span;
// check that a comma comes after every field
if !ate_comma {
let err = self.struct_span_err(self.prev_span, "expected `,`");
if let Some(mut delayed) = delayed_err {
delayed.emit();
}
return Err(err);
}
ate_comma = false;
if self.check(&token::DotDot) || self.token == token::DotDotDot {
etc = true;
let mut etc_sp = self.token.span;
if self.token == token::DotDotDot { // Issue #46718
// Accept `...` as if it were `..` to avoid further errors
self.struct_span_err(self.token.span, "expected field pattern, found `...`")
.span_suggestion(
self.token.span,
"to omit remaining fields, use one fewer `.`",
"..".to_owned(),
Applicability::MachineApplicable
)
.emit();
}
self.bump(); // `..` || `...`
if self.token == token::CloseDelim(token::Brace) {
etc_span = Some(etc_sp);
break;
}
let token_str = self.this_token_descr();
let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
err.span_label(self.token.span, "expected `}`");
let mut comma_sp = None;
if self.token == token::Comma { // Issue #49257
let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span);
etc_sp = etc_sp.to(nw_span);
err.span_label(etc_sp,
"`..` must be at the end and cannot have a trailing comma");
comma_sp = Some(self.token.span);
self.bump();
ate_comma = true;
}
etc_span = Some(etc_sp.until(self.token.span));
if self.token == token::CloseDelim(token::Brace) {
// If the struct looks otherwise well formed, recover and continue.
if let Some(sp) = comma_sp {
err.span_suggestion_short(
sp,
"remove this comma",
String::new(),
Applicability::MachineApplicable,
);
}
err.emit();
break;
} else if self.token.is_ident() && ate_comma {
// Accept fields coming after `..,`.
// This way we avoid "pattern missing fields" errors afterwards.
// We delay this error until the end in order to have a span for a
// suggested fix.
if let Some(mut delayed_err) = delayed_err {
delayed_err.emit();
return Err(err);
} else {
delayed_err = Some(err);
}
} else {
if let Some(mut err) = delayed_err {
err.emit();
}
return Err(err);
}
}
fields.push(match self.parse_pat_field(lo, attrs) {
Ok(field) => field,
Err(err) => {
if let Some(mut delayed_err) = delayed_err {
delayed_err.emit();
}
return Err(err);
}
});
ate_comma = self.eat(&token::Comma);
}
if let Some(mut err) = delayed_err {
if let Some(etc_span) = etc_span {
err.multipart_suggestion(
"move the `..` to the end of the field list",
vec![
(etc_span, String::new()),
(self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
],
Applicability::MachineApplicable,
);
}
err.emit();
}
return Ok((fields, etc));
}
fn parse_pat_field(
&mut self,
lo: Span,
attrs: Vec<Attribute>
) -> PResult<'a, Spanned<FieldPat>> {
// Check if a colon exists one ahead. This means we're parsing a fieldname.
let hi;
let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
// Parsing a pattern of the form "fieldname: pat"
let fieldname = self.parse_field_name()?;
self.bump();
let pat = self.parse_pat(None)?;
hi = pat.span;
(pat, fieldname, false)
} else {
// Parsing a pattern of the form "(box) (ref) (mut) fieldname"
let is_box = self.eat_keyword(kw::Box);
let boxed_span = self.token.span;
let is_ref = self.eat_keyword(kw::Ref);
let is_mut = self.eat_keyword(kw::Mut);
let fieldname = self.parse_ident()?;
hi = self.prev_span;
let bind_type = match (is_ref, is_mut) {
(true, true) => BindingMode::ByRef(Mutability::Mutable),
(true, false) => BindingMode::ByRef(Mutability::Immutable),
(false, true) => BindingMode::ByValue(Mutability::Mutable),
(false, false) => BindingMode::ByValue(Mutability::Immutable),
};
let fieldpat = self.mk_pat_ident(boxed_span.to(hi), bind_type, fieldname);
let subpat = if is_box {
self.mk_pat(lo.to(hi), PatKind::Box(fieldpat))
} else {
fieldpat
};
(subpat, fieldname, true)
};
Ok(Spanned {
span: lo.to(hi),
node: FieldPat {
ident: fieldname,
pat: subpat,
is_shorthand,
attrs: attrs.into(),
}
})
}
pub(super) fn mk_pat_ident(&self, span: Span, bm: BindingMode, ident: Ident) -> P<Pat> {
self.mk_pat(span, PatKind::Ident(bm, ident, None))
}
fn mk_pat(&self, span: Span, node: PatKind) -> P<Pat> {
P(Pat { node, span, id: ast::DUMMY_NODE_ID })
}
}

474
src/libsyntax/parse/parser/path.rs Normal file
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@ -0,0 +1,474 @@
use super::{Parser, PResult, TokenType};
use crate::{maybe_whole, ThinVec};
use crate::ast::{self, QSelf, Path, PathSegment, Ident, ParenthesizedArgs, AngleBracketedArgs};
use crate::ast::{AnonConst, GenericArg, AssocTyConstraint, AssocTyConstraintKind, BlockCheckMode};
use crate::parse::token::{self, Token};
use crate::source_map::{Span, BytePos};
use crate::symbol::kw;
use std::mem;
use log::debug;
use errors::{Applicability};
/// Specifies how to parse a path.
#[derive(Copy, Clone, PartialEq)]
pub enum PathStyle {
/// In some contexts, notably in expressions, paths with generic arguments are ambiguous
/// with something else. For example, in expressions `segment < ....` can be interpreted
/// as a comparison and `segment ( ....` can be interpreted as a function call.
/// In all such contexts the non-path interpretation is preferred by default for practical
/// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
/// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
Expr,
/// In other contexts, notably in types, no ambiguity exists and paths can be written
/// without the disambiguator, e.g., `x<y>` - unambiguously a path.
/// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
Type,
/// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
/// visibilities or attributes.
/// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
/// (paths in "mod" contexts have to be checked later for absence of generic arguments
/// anyway, due to macros), but it is used to avoid weird suggestions about expected
/// tokens when something goes wrong.
Mod,
}
impl<'a> Parser<'a> {
/// Parses a qualified path.
/// Assumes that the leading `<` has been parsed already.
///
/// `qualified_path = <type [as trait_ref]>::path`
///
/// # Examples
/// `<T>::default`
/// `<T as U>::a`
/// `<T as U>::F::a<S>` (without disambiguator)
/// `<T as U>::F::a::<S>` (with disambiguator)
pub(super) fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, Path)> {
let lo = self.prev_span;
let ty = self.parse_ty()?;
// `path` will contain the prefix of the path up to the `>`,
// if any (e.g., `U` in the `<T as U>::*` examples
// above). `path_span` has the span of that path, or an empty
// span in the case of something like `<T>::Bar`.
let (mut path, path_span);
if self.eat_keyword(kw::As) {
let path_lo = self.token.span;
path = self.parse_path(PathStyle::Type)?;
path_span = path_lo.to(self.prev_span);
} else {
path_span = self.token.span.to(self.token.span);
path = ast::Path { segments: Vec::new(), span: path_span };
}
// See doc comment for `unmatched_angle_bracket_count`.
self.expect(&token::Gt)?;
if self.unmatched_angle_bracket_count > 0 {
self.unmatched_angle_bracket_count -= 1;
debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
}
self.expect(&token::ModSep)?;
let qself = QSelf { ty, path_span, position: path.segments.len() };
self.parse_path_segments(&mut path.segments, style)?;
Ok((qself, Path { segments: path.segments, span: lo.to(self.prev_span) }))
}
/// Parses simple paths.
///
/// `path = [::] segment+`
/// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
///
/// # Examples
/// `a::b::C<D>` (without disambiguator)
/// `a::b::C::<D>` (with disambiguator)
/// `Fn(Args)` (without disambiguator)
/// `Fn::(Args)` (with disambiguator)
pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, Path> {
maybe_whole!(self, NtPath, |path| {
if style == PathStyle::Mod &&
path.segments.iter().any(|segment| segment.args.is_some()) {
self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
}
path
});
let lo = self.meta_var_span.unwrap_or(self.token.span);
let mut segments = Vec::new();
let mod_sep_ctxt = self.token.span.ctxt();
if self.eat(&token::ModSep) {
segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
}
self.parse_path_segments(&mut segments, style)?;
Ok(Path { segments, span: lo.to(self.prev_span) })
}
/// Like `parse_path`, but also supports parsing `Word` meta items into paths for
/// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
/// attributes.
pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, Path> {
let meta_ident = match self.token.kind {
token::Interpolated(ref nt) => match **nt {
token::NtMeta(ref meta) => match meta.node {
ast::MetaItemKind::Word => Some(meta.path.clone()),
_ => None,
},
_ => None,
},
_ => None,
};
if let Some(path) = meta_ident {
self.bump();
return Ok(path);
}
self.parse_path(style)
}
crate fn parse_path_segments(&mut self,
segments: &mut Vec<PathSegment>,
style: PathStyle)
-> PResult<'a, ()> {
loop {
let segment = self.parse_path_segment(style)?;
if style == PathStyle::Expr {
// In order to check for trailing angle brackets, we must have finished
// recursing (`parse_path_segment` can indirectly call this function),
// that is, the next token must be the highlighted part of the below example:
//
// `Foo::<Bar as Baz<T>>::Qux`
// ^ here
//
// As opposed to the below highlight (if we had only finished the first
// recursion):
//
// `Foo::<Bar as Baz<T>>::Qux`
// ^ here
//
// `PathStyle::Expr` is only provided at the root invocation and never in
// `parse_path_segment` to recurse and therefore can be checked to maintain
// this invariant.
self.check_trailing_angle_brackets(&segment, token::ModSep);
}
segments.push(segment);
if self.is_import_coupler() || !self.eat(&token::ModSep) {
return Ok(());
}
}
}
pub(super) fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
let ident = self.parse_path_segment_ident()?;
let is_args_start = |token: &Token| match token.kind {
token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
| token::LArrow => true,
_ => false,
};
let check_args_start = |this: &mut Self| {
this.expected_tokens.extend_from_slice(
&[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
);
is_args_start(&this.token)
};
Ok(if style == PathStyle::Type && check_args_start(self) ||
style != PathStyle::Mod && self.check(&token::ModSep)
&& self.look_ahead(1, |t| is_args_start(t)) {
// We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
// it isn't, then we reset the unmatched angle bracket count as we're about to start
// parsing a new path.
if style == PathStyle::Expr {
self.unmatched_angle_bracket_count = 0;
self.max_angle_bracket_count = 0;
}
// Generic arguments are found - `<`, `(`, `::<` or `::(`.
self.eat(&token::ModSep);
let lo = self.token.span;
let args = if self.eat_lt() {
// `<'a, T, A = U>`
let (args, constraints) =
self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
self.expect_gt()?;
let span = lo.to(self.prev_span);
AngleBracketedArgs { args, constraints, span }.into()
} else {
// `(T, U) -> R`
let (inputs, _) = self.parse_paren_comma_seq(|p| p.parse_ty())?;
let span = lo.to(self.prev_span);
let output = if self.eat(&token::RArrow) {
Some(self.parse_ty_common(false, false, false)?)
} else {
None
};
ParenthesizedArgs { inputs, output, span }.into()
};
PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
} else {
// Generic arguments are not found.
PathSegment::from_ident(ident)
})
}
pub(super) fn parse_path_segment_ident(&mut self) -> PResult<'a, Ident> {
match self.token.kind {
token::Ident(name, _) if name.is_path_segment_keyword() => {
let span = self.token.span;
self.bump();
Ok(Ident::new(name, span))
}
_ => self.parse_ident(),
}
}
/// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
/// For the purposes of understanding the parsing logic of generic arguments, this function
/// can be thought of being the same as just calling `self.parse_generic_args()` if the source
/// had the correct amount of leading angle brackets.
///
/// ```ignore (diagnostics)
/// bar::<<<<T as Foo>::Output>();
/// ^^ help: remove extra angle brackets
/// ```
fn parse_generic_args_with_leaning_angle_bracket_recovery(
&mut self,
style: PathStyle,
lo: Span,
) -> PResult<'a, (Vec<GenericArg>, Vec<AssocTyConstraint>)> {
// We need to detect whether there are extra leading left angle brackets and produce an
// appropriate error and suggestion. This cannot be implemented by looking ahead at
// upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
// then there won't be matching `>` tokens to find.
//
// To explain how this detection works, consider the following example:
//
// ```ignore (diagnostics)
// bar::<<<<T as Foo>::Output>();
// ^^ help: remove extra angle brackets
// ```
//
// Parsing of the left angle brackets starts in this function. We start by parsing the
// `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
// `eat_lt`):
//
// *Upcoming tokens:* `<<<<T as Foo>::Output>;`
// *Unmatched count:* 1
// *`parse_path_segment` calls deep:* 0
//
// This has the effect of recursing as this function is called if a `<` character
// is found within the expected generic arguments:
//
// *Upcoming tokens:* `<<<T as Foo>::Output>;`
// *Unmatched count:* 2
// *`parse_path_segment` calls deep:* 1
//
// Eventually we will have recursed until having consumed all of the `<` tokens and
// this will be reflected in the count:
//
// *Upcoming tokens:* `T as Foo>::Output>;`
// *Unmatched count:* 4
// `parse_path_segment` calls deep:* 3
//
// The parser will continue until reaching the first `>` - this will decrement the
// unmatched angle bracket count and return to the parent invocation of this function
// having succeeded in parsing:
//
// *Upcoming tokens:* `::Output>;`
// *Unmatched count:* 3
// *`parse_path_segment` calls deep:* 2
//
// This will continue until the next `>` character which will also return successfully
// to the parent invocation of this function and decrement the count:
//
// *Upcoming tokens:* `;`
// *Unmatched count:* 2
// *`parse_path_segment` calls deep:* 1
//
// At this point, this function will expect to find another matching `>` character but
// won't be able to and will return an error. This will continue all the way up the
// call stack until the first invocation:
//
// *Upcoming tokens:* `;`
// *Unmatched count:* 2
// *`parse_path_segment` calls deep:* 0
//
// In doing this, we have managed to work out how many unmatched leading left angle
// brackets there are, but we cannot recover as the unmatched angle brackets have
// already been consumed. To remedy this, we keep a snapshot of the parser state
// before we do the above. We can then inspect whether we ended up with a parsing error
// and unmatched left angle brackets and if so, restore the parser state before we
// consumed any `<` characters to emit an error and consume the erroneous tokens to
// recover by attempting to parse again.
//
// In practice, the recursion of this function is indirect and there will be other
// locations that consume some `<` characters - as long as we update the count when
// this happens, it isn't an issue.
let is_first_invocation = style == PathStyle::Expr;
// Take a snapshot before attempting to parse - we can restore this later.
let snapshot = if is_first_invocation {
Some(self.clone())
} else {
None
};
debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
match self.parse_generic_args() {
Ok(value) => Ok(value),
Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
// Cancel error from being unable to find `>`. We know the error
// must have been this due to a non-zero unmatched angle bracket
// count.
e.cancel();
// Swap `self` with our backup of the parser state before attempting to parse
// generic arguments.
let snapshot = mem::replace(self, snapshot.unwrap());
debug!(
"parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
snapshot.count={:?}",
snapshot.unmatched_angle_bracket_count,
);
// Eat the unmatched angle brackets.
for _ in 0..snapshot.unmatched_angle_bracket_count {
self.eat_lt();
}
// Make a span over ${unmatched angle bracket count} characters.
let span = lo.with_hi(
lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
);
let plural = snapshot.unmatched_angle_bracket_count > 1;
self.diagnostic()
.struct_span_err(
span,
&format!(
"unmatched angle bracket{}",
if plural { "s" } else { "" }
),
)
.span_suggestion(
span,
&format!(
"remove extra angle bracket{}",
if plural { "s" } else { "" }
),
String::new(),
Applicability::MachineApplicable,
)
.emit();
// Try again without unmatched angle bracket characters.
self.parse_generic_args()
},
Err(e) => Err(e),
}
}
/// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
/// possibly including trailing comma.
fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<AssocTyConstraint>)> {
let mut args = Vec::new();
let mut constraints = Vec::new();
let mut misplaced_assoc_ty_constraints: Vec<Span> = Vec::new();
let mut assoc_ty_constraints: Vec<Span> = Vec::new();
let args_lo = self.token.span;
loop {
if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
// Parse lifetime argument.
args.push(GenericArg::Lifetime(self.expect_lifetime()));
misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
} else if self.check_ident() && self.look_ahead(1,
|t| t == &token::Eq || t == &token::Colon) {
// Parse associated type constraint.
let lo = self.token.span;
let ident = self.parse_ident()?;
let kind = if self.eat(&token::Eq) {
AssocTyConstraintKind::Equality {
ty: self.parse_ty()?,
}
} else if self.eat(&token::Colon) {
AssocTyConstraintKind::Bound {
bounds: self.parse_generic_bounds(Some(self.prev_span))?,
}
} else {
unreachable!();
};
let span = lo.to(self.prev_span);
constraints.push(AssocTyConstraint {
id: ast::DUMMY_NODE_ID,
ident,
kind,
span,
});
assoc_ty_constraints.push(span);
} else if self.check_const_arg() {
// Parse const argument.
let expr = if let token::OpenDelim(token::Brace) = self.token.kind {
self.parse_block_expr(
None, self.token.span, BlockCheckMode::Default, ThinVec::new()
)?
} else if self.token.is_ident() {
// FIXME(const_generics): to distinguish between idents for types and consts,
// we should introduce a GenericArg::Ident in the AST and distinguish when
// lowering to the HIR. For now, idents for const args are not permitted.
if self.token.is_keyword(kw::True) || self.token.is_keyword(kw::False) {
self.parse_literal_maybe_minus()?
} else {
return Err(
self.fatal("identifiers may currently not be used for const generics")
);
}
} else {
self.parse_literal_maybe_minus()?
};
let value = AnonConst {
id: ast::DUMMY_NODE_ID,
value: expr,
};
args.push(GenericArg::Const(value));
misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
} else if self.check_type() {
// Parse type argument.
args.push(GenericArg::Type(self.parse_ty()?));
misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
} else {
break
}
if !self.eat(&token::Comma) {
break
}
}
// FIXME: we would like to report this in ast_validation instead, but we currently do not
// preserve ordering of generic parameters with respect to associated type binding, so we
// lose that information after parsing.
if misplaced_assoc_ty_constraints.len() > 0 {
let mut err = self.struct_span_err(
args_lo.to(self.prev_span),
"associated type bindings must be declared after generic parameters",
);
for span in misplaced_assoc_ty_constraints {
err.span_label(
span,
"this associated type binding should be moved after the generic parameters",
);
}
err.emit();
}
Ok((args, constraints))
}
}

458
src/libsyntax/parse/parser/stmt.rs Normal file
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@ -0,0 +1,458 @@
use super::{Parser, PResult, Restrictions, PrevTokenKind, SemiColonMode, BlockMode};
use super::expr::LhsExpr;
use super::path::PathStyle;
use crate::ptr::P;
use crate::{maybe_whole, ThinVec};
use crate::ast::{self, Stmt, StmtKind, Local, Block, BlockCheckMode, Expr, ExprKind};
use crate::ast::{Attribute, AttrStyle, VisibilityKind, MacStmtStyle, Mac_, MacDelimiter};
use crate::ext::base::DummyResult;
use crate::parse::{classify, DirectoryOwnership};
use crate::parse::diagnostics::Error;
use crate::parse::token::{self};
use crate::source_map::{respan, Span};
use crate::symbol::{kw, sym};
use std::mem;
use errors::Applicability;
impl<'a> Parser<'a> {
/// Parse a statement. This stops just before trailing semicolons on everything but items.
/// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
Ok(self.parse_stmt_(true))
}
fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
e.emit();
self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
None
})
}
fn parse_stmt_without_recovery(
&mut self,
macro_legacy_warnings: bool,
) -> PResult<'a, Option<Stmt>> {
maybe_whole!(self, NtStmt, |x| Some(x));
let attrs = self.parse_outer_attributes()?;
let lo = self.token.span;
Ok(Some(if self.eat_keyword(kw::Let) {
Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Local(self.parse_local(attrs.into())?),
span: lo.to(self.prev_span),
}
} else if let Some(macro_def) = self.eat_macro_def(
&attrs,
&respan(lo, VisibilityKind::Inherited),
lo,
)? {
Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Item(macro_def),
span: lo.to(self.prev_span),
}
// Starts like a simple path, being careful to avoid contextual keywords
// such as a union items, item with `crate` visibility or auto trait items.
// Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
// like a path (1 token), but it fact not a path.
// `union::b::c` - path, `union U { ... }` - not a path.
// `crate::b::c` - path, `crate struct S;` - not a path.
} else if self.token.is_path_start() &&
!self.token.is_qpath_start() &&
!self.is_union_item() &&
!self.is_crate_vis() &&
!self.is_auto_trait_item() &&
!self.is_async_fn() {
let path = self.parse_path(PathStyle::Expr)?;
if !self.eat(&token::Not) {
let expr = if self.check(&token::OpenDelim(token::Brace)) {
self.parse_struct_expr(lo, path, ThinVec::new())?
} else {
let hi = self.prev_span;
self.mk_expr(lo.to(hi), ExprKind::Path(None, path), ThinVec::new())
};
let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
})?;
return Ok(Some(Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Expr(expr),
span: lo.to(self.prev_span),
}));
}
let (delim, tts) = self.expect_delimited_token_tree()?;
let hi = self.prev_span;
let style = if delim == MacDelimiter::Brace {
MacStmtStyle::Braces
} else {
MacStmtStyle::NoBraces
};
let mac = respan(lo.to(hi), Mac_ {
path,
tts,
delim,
prior_type_ascription: self.last_type_ascription,
});
let node = if delim == MacDelimiter::Brace ||
self.token == token::Semi || self.token == token::Eof {
StmtKind::Mac(P((mac, style, attrs.into())))
}
// We used to incorrectly stop parsing macro-expanded statements here.
// If the next token will be an error anyway but could have parsed with the
// earlier behavior, stop parsing here and emit a warning to avoid breakage.
else if macro_legacy_warnings &&
self.token.can_begin_expr() &&
match self.token.kind {
// These can continue an expression, so we can't stop parsing and warn.
token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
token::BinOp(token::Minus) | token::BinOp(token::Star) |
token::BinOp(token::And) | token::BinOp(token::Or) |
token::AndAnd | token::OrOr |
token::DotDot | token::DotDotDot | token::DotDotEq => false,
_ => true,
} {
self.warn_missing_semicolon();
StmtKind::Mac(P((mac, style, attrs.into())))
} else {
let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
let e = self.maybe_recover_from_bad_qpath(e, true)?;
let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
StmtKind::Expr(e)
};
Stmt {
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
node,
}
} else {
// FIXME: Bad copy of attrs
let old_directory_ownership =
mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
let item = self.parse_item_(attrs.clone(), false, true)?;
self.directory.ownership = old_directory_ownership;
match item {
Some(i) => Stmt {
id: ast::DUMMY_NODE_ID,
span: lo.to(i.span),
node: StmtKind::Item(i),
},
None => {
let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
if !attrs.is_empty() {
if s.prev_token_kind == PrevTokenKind::DocComment {
s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
} else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
s.span_err(
s.token.span, "expected statement after outer attribute"
);
}
}
};
// Do not attempt to parse an expression if we're done here.
if self.token == token::Semi {
unused_attrs(&attrs, self);
self.bump();
return Ok(None);
}
if self.token == token::CloseDelim(token::Brace) {
unused_attrs(&attrs, self);
return Ok(None);
}
// Remainder are line-expr stmts.
let e = self.parse_expr_res(
Restrictions::STMT_EXPR, Some(attrs.into()))?;
Stmt {
id: ast::DUMMY_NODE_ID,
span: lo.to(e.span),
node: StmtKind::Expr(e),
}
}
}
}))
}
/// Parses a local variable declaration.
fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
let lo = self.prev_span;
let pat = self.parse_top_level_pat()?;
let (err, ty) = if self.eat(&token::Colon) {
// Save the state of the parser before parsing type normally, in case there is a `:`
// instead of an `=` typo.
let parser_snapshot_before_type = self.clone();
let colon_sp = self.prev_span;
match self.parse_ty() {
Ok(ty) => (None, Some(ty)),
Err(mut err) => {
// Rewind to before attempting to parse the type and continue parsing
let parser_snapshot_after_type = self.clone();
mem::replace(self, parser_snapshot_before_type);
let snippet = self.span_to_snippet(pat.span).unwrap();
err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
(Some((parser_snapshot_after_type, colon_sp, err)), None)
}
}
} else {
(None, None)
};
let init = match (self.parse_initializer(err.is_some()), err) {
(Ok(init), None) => { // init parsed, ty parsed
init
}
(Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
// Could parse the type as if it were the initializer, it is likely there was a
// typo in the code: `:` instead of `=`. Add suggestion and emit the error.
err.span_suggestion_short(
colon_sp,
"use `=` if you meant to assign",
"=".to_string(),
Applicability::MachineApplicable
);
err.emit();
// As this was parsed successfully, continue as if the code has been fixed for the
// rest of the file. It will still fail due to the emitted error, but we avoid
// extra noise.
init
}
(Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
init_err.cancel();
// Couldn't parse the type nor the initializer, only raise the type error and
// return to the parser state before parsing the type as the initializer.
// let x: <parse_error>;
mem::replace(self, snapshot);
return Err(ty_err);
}
(Err(err), None) => { // init error, ty parsed
// Couldn't parse the initializer and we're not attempting to recover a failed
// parse of the type, return the error.
return Err(err);
}
};
let hi = if self.token == token::Semi {
self.token.span
} else {
self.prev_span
};
Ok(P(ast::Local {
ty,
pat,
init,
id: ast::DUMMY_NODE_ID,
span: lo.to(hi),
attrs,
}))
}
/// Parses the RHS of a local variable declaration (e.g., '= 14;').
fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
if self.eat(&token::Eq) {
Ok(Some(self.parse_expr()?))
} else if skip_eq {
Ok(Some(self.parse_expr()?))
} else {
Ok(None)
}
}
fn is_auto_trait_item(&self) -> bool {
// auto trait
(self.token.is_keyword(kw::Auto) &&
self.is_keyword_ahead(1, &[kw::Trait]))
|| // unsafe auto trait
(self.token.is_keyword(kw::Unsafe) &&
self.is_keyword_ahead(1, &[kw::Auto]) &&
self.is_keyword_ahead(2, &[kw::Trait]))
}
/// Parses a block. No inner attributes are allowed.
pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
maybe_whole!(self, NtBlock, |x| x);
let lo = self.token.span;
if !self.eat(&token::OpenDelim(token::Brace)) {
let sp = self.token.span;
let tok = self.this_token_descr();
let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
let do_not_suggest_help =
self.token.is_keyword(kw::In) || self.token == token::Colon;
if self.token.is_ident_named(sym::and) {
e.span_suggestion_short(
self.token.span,
"use `&&` instead of `and` for the boolean operator",
"&&".to_string(),
Applicability::MaybeIncorrect,
);
}
if self.token.is_ident_named(sym::or) {
e.span_suggestion_short(
self.token.span,
"use `||` instead of `or` for the boolean operator",
"||".to_string(),
Applicability::MaybeIncorrect,
);
}
// Check to see if the user has written something like
//
// if (cond)
// bar;
//
// Which is valid in other languages, but not Rust.
match self.parse_stmt_without_recovery(false) {
Ok(Some(stmt)) => {
if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
|| do_not_suggest_help {
// if the next token is an open brace (e.g., `if a b {`), the place-
// inside-a-block suggestion would be more likely wrong than right
e.span_label(sp, "expected `{`");
return Err(e);
}
let mut stmt_span = stmt.span;
// expand the span to include the semicolon, if it exists
if self.eat(&token::Semi) {
stmt_span = stmt_span.with_hi(self.prev_span.hi());
}
if let Ok(snippet) = self.span_to_snippet(stmt_span) {
e.span_suggestion(
stmt_span,
"try placing this code inside a block",
format!("{{ {} }}", snippet),
// speculative, has been misleading in the past (#46836)
Applicability::MaybeIncorrect,
);
}
}
Err(mut e) => {
self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
self.cancel(&mut e);
}
_ => ()
}
e.span_label(sp, "expected `{`");
return Err(e);
}
self.parse_block_tail(lo, BlockCheckMode::Default)
}
/// Parses a block. Inner attributes are allowed.
crate fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
let lo = self.token.span;
self.expect(&token::OpenDelim(token::Brace))?;
Ok((self.parse_inner_attributes()?,
self.parse_block_tail(lo, BlockCheckMode::Default)?))
}
/// Parses the rest of a block expression or function body.
/// Precondition: already parsed the '{'.
pub(super) fn parse_block_tail(
&mut self,
lo: Span,
s: BlockCheckMode
) -> PResult<'a, P<Block>> {
let mut stmts = vec![];
while !self.eat(&token::CloseDelim(token::Brace)) {
if self.token == token::Eof {
break;
}
let stmt = match self.parse_full_stmt(false) {
Err(mut err) => {
err.emit();
self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
Some(Stmt {
id: ast::DUMMY_NODE_ID,
node: StmtKind::Expr(DummyResult::raw_expr(self.token.span, true)),
span: self.token.span,
})
}
Ok(stmt) => stmt,
};
if let Some(stmt) = stmt {
stmts.push(stmt);
} else {
// Found only `;` or `}`.
continue;
};
}
Ok(P(ast::Block {
stmts,
id: ast::DUMMY_NODE_ID,
rules: s,
span: lo.to(self.prev_span),
}))
}
/// Parses a statement, including the trailing semicolon.
crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
// skip looking for a trailing semicolon when we have an interpolated statement
maybe_whole!(self, NtStmt, |x| Some(x));
let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
Some(stmt) => stmt,
None => return Ok(None),
};
match stmt.node {
StmtKind::Expr(ref expr) if self.token != token::Eof => {
// expression without semicolon
if classify::expr_requires_semi_to_be_stmt(expr) {
// Just check for errors and recover; do not eat semicolon yet.
if let Err(mut e) =
self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
{
e.emit();
self.recover_stmt();
// Don't complain about type errors in body tail after parse error (#57383).
let sp = expr.span.to(self.prev_span);
stmt.node = StmtKind::Expr(DummyResult::raw_expr(sp, true));
}
}
}
StmtKind::Local(..) => {
// We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
if macro_legacy_warnings && self.token != token::Semi {
self.warn_missing_semicolon();
} else {
self.expect_one_of(&[], &[token::Semi])?;
}
}
_ => {}
}
if self.eat(&token::Semi) {
stmt = stmt.add_trailing_semicolon();
}
stmt.span = stmt.span.to(self.prev_span);
Ok(Some(stmt))
}
fn warn_missing_semicolon(&self) {
self.diagnostic().struct_span_warn(self.token.span, {
&format!("expected `;`, found {}", self.this_token_descr())
}).note({
"This was erroneously allowed and will become a hard error in a future release"
}).emit();
}
}

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src/libsyntax/parse/parser/ty.rs Normal file
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use super::{Parser, PResult, PathStyle, PrevTokenKind, TokenType};
use crate::{maybe_whole, maybe_recover_from_interpolated_ty_qpath};
use crate::ptr::P;
use crate::ast::{self, Ty, TyKind, MutTy, BareFnTy, FunctionRetTy, GenericParam, Lifetime, Ident};
use crate::ast::{TraitBoundModifier, TraitObjectSyntax, GenericBound, GenericBounds, PolyTraitRef};
use crate::ast::{Mutability, AnonConst, FnDecl, Mac_};
use crate::parse::token::{self, Token};
use crate::source_map::{respan, Span};
use crate::symbol::{kw};
use rustc_target::spec::abi::Abi;
use errors::{Applicability};
/// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
/// `IDENT<<u8 as Trait>::AssocTy>`.
///
/// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
/// that `IDENT` is not the ident of a fn trait.
fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
t == &token::ModSep || t == &token::Lt ||
t == &token::BinOp(token::Shl)
}
impl<'a> Parser<'a> {
/// Parses a type.
pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
self.parse_ty_common(true, true, false)
}
/// Parses a type in restricted contexts where `+` is not permitted.
///
/// Example 1: `&'a TYPE`
/// `+` is prohibited to maintain operator priority (P(+) < P(&)).
/// Example 2: `value1 as TYPE + value2`
/// `+` is prohibited to avoid interactions with expression grammar.
pub(super) fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
self.parse_ty_common(false, true, false)
}
/// Parses an optional return type `[ -> TY ]` in a function declaration.
pub(super) fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
if self.eat(&token::RArrow) {
Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
} else {
Ok(FunctionRetTy::Default(self.token.span.shrink_to_lo()))
}
}
pub(super) fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
maybe_whole!(self, NtTy, |x| x);
let lo = self.token.span;
let mut impl_dyn_multi = false;
let node = if self.eat(&token::OpenDelim(token::Paren)) {
// `(TYPE)` is a parenthesized type.
// `(TYPE,)` is a tuple with a single field of type TYPE.
let mut ts = vec![];
let mut last_comma = false;
while self.token != token::CloseDelim(token::Paren) {
ts.push(self.parse_ty()?);
if self.eat(&token::Comma) {
last_comma = true;
} else {
last_comma = false;
break;
}
}
let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
self.expect(&token::CloseDelim(token::Paren))?;
if ts.len() == 1 && !last_comma {
let ty = ts.into_iter().nth(0).unwrap().into_inner();
let maybe_bounds = allow_plus && self.token.is_like_plus();
match ty.node {
// `(TY_BOUND_NOPAREN) + BOUND + ...`.
TyKind::Path(None, ref path) if maybe_bounds => {
self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
}
TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
let path = match bounds[0] {
GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
};
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
}
// `(TYPE)`
_ => TyKind::Paren(P(ty))
}
} else {
TyKind::Tup(ts)
}
} else if self.eat(&token::Not) {
// Never type `!`
TyKind::Never
} else if self.eat(&token::BinOp(token::Star)) {
// Raw pointer
TyKind::Ptr(self.parse_ptr()?)
} else if self.eat(&token::OpenDelim(token::Bracket)) {
// Array or slice
let t = self.parse_ty()?;
// Parse optional `; EXPR` in `[TYPE; EXPR]`
let t = match self.maybe_parse_fixed_length_of_vec()? {
None => TyKind::Slice(t),
Some(length) => TyKind::Array(t, AnonConst {
id: ast::DUMMY_NODE_ID,
value: length,
}),
};
self.expect(&token::CloseDelim(token::Bracket))?;
t
} else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
// Reference
self.expect_and()?;
self.parse_borrowed_pointee()?
} else if self.eat_keyword_noexpect(kw::Typeof) {
// `typeof(EXPR)`
// In order to not be ambiguous, the type must be surrounded by parens.
self.expect(&token::OpenDelim(token::Paren))?;
let e = AnonConst {
id: ast::DUMMY_NODE_ID,
value: self.parse_expr()?,
};
self.expect(&token::CloseDelim(token::Paren))?;
TyKind::Typeof(e)
} else if self.eat_keyword(kw::Underscore) {
// A type to be inferred `_`
TyKind::Infer
} else if self.token_is_bare_fn_keyword() {
// Function pointer type
self.parse_ty_bare_fn(Vec::new())?
} else if self.check_keyword(kw::For) {
// Function pointer type or bound list (trait object type) starting with a poly-trait.
// `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
// `for<'lt> Trait1<'lt> + Trait2 + 'a`
let lo = self.token.span;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
if self.token_is_bare_fn_keyword() {
self.parse_ty_bare_fn(lifetime_defs)?
} else {
let path = self.parse_path(PathStyle::Type)?;
let parse_plus = allow_plus && self.check_plus();
self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
}
} else if self.eat_keyword(kw::Impl) {
// Always parse bounds greedily for better error recovery.
let bounds = self.parse_generic_bounds(None)?;
impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
} else if self.check_keyword(kw::Dyn) &&
(self.token.span.rust_2018() ||
self.look_ahead(1, |t| t.can_begin_bound() &&
!can_continue_type_after_non_fn_ident(t))) {
self.bump(); // `dyn`
// Always parse bounds greedily for better error recovery.
let bounds = self.parse_generic_bounds(None)?;
impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
} else if self.check(&token::Question) ||
self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
// Bound list (trait object type)
TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
TraitObjectSyntax::None)
} else if self.eat_lt() {
// Qualified path
let (qself, path) = self.parse_qpath(PathStyle::Type)?;
TyKind::Path(Some(qself), path)
} else if self.token.is_path_start() {
// Simple path
let path = self.parse_path(PathStyle::Type)?;
if self.eat(&token::Not) {
// Macro invocation in type position
let (delim, tts) = self.expect_delimited_token_tree()?;
let node = Mac_ {
path,
tts,
delim,
prior_type_ascription: self.last_type_ascription,
};
TyKind::Mac(respan(lo.to(self.prev_span), node))
} else {
// Just a type path or bound list (trait object type) starting with a trait.
// `Type`
// `Trait1 + Trait2 + 'a`
if allow_plus && self.check_plus() {
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
} else {
TyKind::Path(None, path)
}
}
} else if self.check(&token::DotDotDot) {
if allow_c_variadic {
self.eat(&token::DotDotDot);
TyKind::CVarArgs
} else {
return Err(self.fatal(
"only foreign functions are allowed to be C-variadic"
));
}
} else {
let msg = format!("expected type, found {}", self.this_token_descr());
let mut err = self.fatal(&msg);
err.span_label(self.token.span, "expected type");
self.maybe_annotate_with_ascription(&mut err, true);
return Err(err);
};
let span = lo.to(self.prev_span);
let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
// Try to recover from use of `+` with incorrect priority.
self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
}
fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
if parse_plus {
self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
}
Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
}
fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
let mutbl = if self.eat_keyword(kw::Mut) {
Mutability::Mutable
} else if self.eat_keyword(kw::Const) {
Mutability::Immutable
} else {
let span = self.prev_span;
let msg = "expected mut or const in raw pointer type";
self.struct_span_err(span, msg)
.span_label(span, msg)
.help("use `*mut T` or `*const T` as appropriate")
.emit();
Mutability::Immutable
};
let t = self.parse_ty_no_plus()?;
Ok(MutTy { ty: t, mutbl })
}
fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
if self.eat(&token::Semi) {
Ok(Some(self.parse_expr()?))
} else {
Ok(None)
}
}
fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
let mutbl = self.parse_mutability();
let ty = self.parse_ty_no_plus()?;
return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }));
}
/// Is the current token one of the keywords that signals a bare function type?
fn token_is_bare_fn_keyword(&mut self) -> bool {
self.check_keyword(kw::Fn) ||
self.check_keyword(kw::Unsafe) ||
self.check_keyword(kw::Extern)
}
/// Parses a `TyKind::BareFn` type.
fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
/*
[unsafe] [extern "ABI"] fn (S) -> T
^~~~^ ^~~~^ ^~^ ^
| | | |
| | | Return type
| | Argument types
| |
| ABI
Function Style
*/
let unsafety = self.parse_unsafety();
let abi = if self.eat_keyword(kw::Extern) {
self.parse_opt_abi()?.unwrap_or(Abi::C)
} else {
Abi::Rust
};
self.expect_keyword(kw::Fn)?;
let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
let ret_ty = self.parse_ret_ty(false)?;
let decl = P(FnDecl {
inputs,
output: ret_ty,
c_variadic,
});
Ok(TyKind::BareFn(P(BareFnTy {
abi,
unsafety,
generic_params,
decl,
})))
}
crate fn parse_generic_bounds(&mut self,
colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
self.parse_generic_bounds_common(true, colon_span)
}
/// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
///
/// ```
/// BOUND = TY_BOUND | LT_BOUND
/// LT_BOUND = LIFETIME (e.g., `'a`)
/// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
/// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
/// ```
fn parse_generic_bounds_common(&mut self,
allow_plus: bool,
colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
let mut bounds = Vec::new();
let mut negative_bounds = Vec::new();
let mut last_plus_span = None;
let mut was_negative = false;
loop {
// This needs to be synchronized with `TokenKind::can_begin_bound`.
let is_bound_start = self.check_path() || self.check_lifetime() ||
self.check(&token::Not) || // used for error reporting only
self.check(&token::Question) ||
self.check_keyword(kw::For) ||
self.check(&token::OpenDelim(token::Paren));
if is_bound_start {
let lo = self.token.span;
let has_parens = self.eat(&token::OpenDelim(token::Paren));
let inner_lo = self.token.span;
let is_negative = self.eat(&token::Not);
let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
if self.token.is_lifetime() {
if let Some(question_span) = question {
self.span_err(question_span,
"`?` may only modify trait bounds, not lifetime bounds");
}
bounds.push(GenericBound::Outlives(self.expect_lifetime()));
if has_parens {
let inner_span = inner_lo.to(self.prev_span);
self.expect(&token::CloseDelim(token::Paren))?;
let mut err = self.struct_span_err(
lo.to(self.prev_span),
"parenthesized lifetime bounds are not supported"
);
if let Ok(snippet) = self.span_to_snippet(inner_span) {
err.span_suggestion_short(
lo.to(self.prev_span),
"remove the parentheses",
snippet.to_owned(),
Applicability::MachineApplicable
);
}
err.emit();
}
} else {
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
let path = self.parse_path(PathStyle::Type)?;
if has_parens {
self.expect(&token::CloseDelim(token::Paren))?;
}
let poly_span = lo.to(self.prev_span);
if is_negative {
was_negative = true;
if let Some(sp) = last_plus_span.or(colon_span) {
negative_bounds.push(sp.to(poly_span));
}
} else {
let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
let modifier = if question.is_some() {
TraitBoundModifier::Maybe
} else {
TraitBoundModifier::None
};
bounds.push(GenericBound::Trait(poly_trait, modifier));
}
}
} else {
break
}
if !allow_plus || !self.eat_plus() {
break
} else {
last_plus_span = Some(self.prev_span);
}
}
if !negative_bounds.is_empty() || was_negative {
let plural = negative_bounds.len() > 1;
let last_span = negative_bounds.last().map(|sp| *sp);
let mut err = self.struct_span_err(
negative_bounds,
"negative trait bounds are not supported",
);
if let Some(sp) = last_span {
err.span_label(sp, "negative trait bounds are not supported");
}
if let Some(bound_list) = colon_span {
let bound_list = bound_list.to(self.prev_span);
let mut new_bound_list = String::new();
if !bounds.is_empty() {
let mut snippets = bounds.iter().map(|bound| bound.span())
.map(|span| self.span_to_snippet(span));
while let Some(Ok(snippet)) = snippets.next() {
new_bound_list.push_str(" + ");
new_bound_list.push_str(&snippet);
}
new_bound_list = new_bound_list.replacen(" +", ":", 1);
}
err.span_suggestion_hidden(
bound_list,
&format!("remove the trait bound{}", if plural { "s" } else { "" }),
new_bound_list,
Applicability::MachineApplicable,
);
}
err.emit();
}
return Ok(bounds);
}
pub(super) fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
if self.eat_keyword(kw::For) {
self.expect_lt()?;
let params = self.parse_generic_params()?;
self.expect_gt()?;
// We rely on AST validation to rule out invalid cases: There must not be type
// parameters, and the lifetime parameters must not have bounds.
Ok(params)
} else {
Ok(Vec::new())
}
}
crate fn check_lifetime(&mut self) -> bool {
self.expected_tokens.push(TokenType::Lifetime);
self.token.is_lifetime()
}
/// Parses a single lifetime `'a` or panics.
crate fn expect_lifetime(&mut self) -> Lifetime {
if let Some(ident) = self.token.lifetime() {
let span = self.token.span;
self.bump();
Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
} else {
self.span_bug(self.token.span, "not a lifetime")
}
}
}