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extract pattern lowering -> pat.rs

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This commit is contained in:
Mazdak Farrokhzad 2020-01-06 05:51:59 +01:00
parent 956265d55b
commit f75ccdef10
2 changed files with 256 additions and 246 deletions
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249
src/librustc_ast_lowering/lib.rs
View file

@ -33,6 +33,7 @@
//! in the HIR, especially for multiple identifiers.
#![feature(array_value_iter)]
#![feature(crate_visibility_modifier)]
use rustc::arena::Arena;
use rustc::dep_graph::DepGraph;
@ -58,14 +59,13 @@ use rustc_session::config::nightly_options;
use rustc_session::node_id::NodeMap;
use rustc_session::Session;
use rustc_span::hygiene::ExpnId;
use rustc_span::source_map::{respan, DesugaringKind, ExpnData, ExpnKind, Spanned};
use rustc_span::source_map::{respan, DesugaringKind, ExpnData, ExpnKind};
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_span::Span;
use syntax::ast;
use syntax::ast::*;
use syntax::attr;
use syntax::print::pprust;
use syntax::ptr::P as AstP;
use syntax::sess::ParseSess;
use syntax::token::{self, Nonterminal, Token};
use syntax::tokenstream::{TokenStream, TokenTree};
@ -86,6 +86,7 @@ macro_rules! arena_vec {
mod expr;
mod item;
mod pat;
const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
@ -2636,250 +2637,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
self.expr_block(block, AttrVec::new())
}
fn lower_pat(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> {
let node = match p.kind {
PatKind::Wild => hir::PatKind::Wild,
PatKind::Ident(ref binding_mode, ident, ref sub) => {
let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(&*s));
let node = self.lower_pat_ident(p, binding_mode, ident, lower_sub);
node
}
PatKind::Lit(ref e) => hir::PatKind::Lit(self.lower_expr(e)),
PatKind::TupleStruct(ref path, ref pats) => {
let qpath = self.lower_qpath(
p.id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct");
hir::PatKind::TupleStruct(qpath, pats, ddpos)
}
PatKind::Or(ref pats) => {
hir::PatKind::Or(self.arena.alloc_from_iter(pats.iter().map(|x| self.lower_pat(x))))
}
PatKind::Path(ref qself, ref path) => {
let qpath = self.lower_qpath(
p.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
hir::PatKind::Path(qpath)
}
PatKind::Struct(ref path, ref fields, etc) => {
let qpath = self.lower_qpath(
p.id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
let fs = self.arena.alloc_from_iter(fields.iter().map(|f| hir::FieldPat {
hir_id: self.next_id(),
ident: f.ident,
pat: self.lower_pat(&f.pat),
is_shorthand: f.is_shorthand,
span: f.span,
}));
hir::PatKind::Struct(qpath, fs, etc)
}
PatKind::Tuple(ref pats) => {
let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");
hir::PatKind::Tuple(pats, ddpos)
}
PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
PatKind::Ref(ref inner, mutbl) => hir::PatKind::Ref(self.lower_pat(inner), mutbl),
PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range(
self.lower_expr(e1),
self.lower_expr(e2),
self.lower_range_end(end),
),
PatKind::Slice(ref pats) => self.lower_pat_slice(pats),
PatKind::Rest => {
// If we reach here the `..` pattern is not semantically allowed.
self.ban_illegal_rest_pat(p.span)
}
PatKind::Paren(ref inner) => return self.lower_pat(inner),
PatKind::Mac(_) => panic!("Shouldn't exist here"),
};
self.pat_with_node_id_of(p, node)
}
fn lower_pat_tuple(
&mut self,
pats: &[AstP<Pat>],
ctx: &str,
) -> (&'hir [&'hir hir::Pat<'hir>], Option<usize>) {
let mut elems = Vec::with_capacity(pats.len());
let mut rest = None;
let mut iter = pats.iter().enumerate();
for (idx, pat) in iter.by_ref() {
// Interpret the first `..` pattern as a sub-tuple pattern.
// Note that unlike for slice patterns,
// where `xs @ ..` is a legal sub-slice pattern,
// it is not a legal sub-tuple pattern.
if pat.is_rest() {
rest = Some((idx, pat.span));
break;
}
// It was not a sub-tuple pattern so lower it normally.
elems.push(self.lower_pat(pat));
}
for (_, pat) in iter {
// There was a previous sub-tuple pattern; make sure we don't allow more...
if pat.is_rest() {
// ...but there was one again, so error.
self.ban_extra_rest_pat(pat.span, rest.unwrap().1, ctx);
} else {
elems.push(self.lower_pat(pat));
}
}
(self.arena.alloc_from_iter(elems), rest.map(|(ddpos, _)| ddpos))
}
/// Lower a slice pattern of form `[pat_0, ..., pat_n]` into
/// `hir::PatKind::Slice(before, slice, after)`.
///
/// When encountering `($binding_mode $ident @)? ..` (`slice`),
/// this is interpreted as a sub-slice pattern semantically.
/// Patterns that follow, which are not like `slice` -- or an error occurs, are in `after`.
fn lower_pat_slice(&mut self, pats: &[AstP<Pat>]) -> hir::PatKind<'hir> {
let mut before = Vec::new();
let mut after = Vec::new();
let mut slice = None;
let mut prev_rest_span = None;
let mut iter = pats.iter();
// Lower all the patterns until the first occurence of a sub-slice pattern.
for pat in iter.by_ref() {
match pat.kind {
// Found a sub-slice pattern `..`. Record, lower it to `_`, and stop here.
PatKind::Rest => {
prev_rest_span = Some(pat.span);
slice = Some(self.pat_wild_with_node_id_of(pat));
break;
}
// Found a sub-slice pattern `$binding_mode $ident @ ..`.
// Record, lower it to `$binding_mode $ident @ _`, and stop here.
PatKind::Ident(ref bm, ident, Some(ref sub)) if sub.is_rest() => {
prev_rest_span = Some(sub.span);
let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub));
let node = self.lower_pat_ident(pat, bm, ident, lower_sub);
slice = Some(self.pat_with_node_id_of(pat, node));
break;
}
// It was not a subslice pattern so lower it normally.
_ => before.push(self.lower_pat(pat)),
}
}
// Lower all the patterns after the first sub-slice pattern.
for pat in iter {
// There was a previous subslice pattern; make sure we don't allow more.
let rest_span = match pat.kind {
PatKind::Rest => Some(pat.span),
PatKind::Ident(.., Some(ref sub)) if sub.is_rest() => {
// The `HirValidator` is merciless; add a `_` pattern to avoid ICEs.
after.push(self.pat_wild_with_node_id_of(pat));
Some(sub.span)
}
_ => None,
};
if let Some(rest_span) = rest_span {
// We have e.g., `[a, .., b, ..]`. That's no good, error!
self.ban_extra_rest_pat(rest_span, prev_rest_span.unwrap(), "slice");
} else {
// Lower the pattern normally.
after.push(self.lower_pat(pat));
}
}
hir::PatKind::Slice(
self.arena.alloc_from_iter(before),
slice,
self.arena.alloc_from_iter(after),
)
}
fn lower_pat_ident(
&mut self,
p: &Pat,
binding_mode: &BindingMode,
ident: Ident,
lower_sub: impl FnOnce(&mut Self) -> Option<&'hir hir::Pat<'hir>>,
) -> hir::PatKind<'hir> {
match self.resolver.get_partial_res(p.id).map(|d| d.base_res()) {
// `None` can occur in body-less function signatures
res @ None | res @ Some(Res::Local(_)) => {
let canonical_id = match res {
Some(Res::Local(id)) => id,
_ => p.id,
};
hir::PatKind::Binding(
self.lower_binding_mode(binding_mode),
self.lower_node_id(canonical_id),
ident,
lower_sub(self),
)
}
Some(res) => hir::PatKind::Path(hir::QPath::Resolved(
None,
self.arena.alloc(hir::Path {
span: ident.span,
res: self.lower_res(res),
segments: arena_vec![self; hir::PathSegment::from_ident(ident)],
}),
)),
}
}
fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> {
self.pat_with_node_id_of(p, hir::PatKind::Wild)
}
/// Construct a `Pat` with the `HirId` of `p.id` lowered.
fn pat_with_node_id_of(&mut self, p: &Pat, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> {
self.arena.alloc(hir::Pat { hir_id: self.lower_node_id(p.id), kind, span: p.span })
}
/// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern.
fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) {
self.diagnostic()
.struct_span_err(sp, &format!("`..` can only be used once per {} pattern", ctx))
.span_label(sp, &format!("can only be used once per {} pattern", ctx))
.span_label(prev_sp, "previously used here")
.emit();
}
/// Used to ban the `..` pattern in places it shouldn't be semantically.
fn ban_illegal_rest_pat(&self, sp: Span) -> hir::PatKind<'hir> {
self.diagnostic()
.struct_span_err(sp, "`..` patterns are not allowed here")
.note("only allowed in tuple, tuple struct, and slice patterns")
.emit();
// We're not in a list context so `..` can be reasonably treated
// as `_` because it should always be valid and roughly matches the
// intent of `..` (notice that the rest of a single slot is that slot).
hir::PatKind::Wild
}
fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd {
match *e {
RangeEnd::Included(_) => hir::RangeEnd::Included,
RangeEnd::Excluded => hir::RangeEnd::Excluded,
}
}
fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
self.with_new_scopes(|this| hir::AnonConst {
hir_id: this.lower_node_id(c.id),

253
src/librustc_ast_lowering/pat.rs Normal file
View file

@ -0,0 +1,253 @@
use super::{ImplTraitContext, LoweringContext, ParamMode};
use rustc::hir;
use rustc::hir::def::Res;
use rustc_span::{source_map::Spanned, Span};
use syntax::ast::*;
use syntax::ptr::P;
impl<'a, 'hir> LoweringContext<'a, 'hir> {
crate fn lower_pat(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> {
let node = match p.kind {
PatKind::Wild => hir::PatKind::Wild,
PatKind::Ident(ref binding_mode, ident, ref sub) => {
let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(&*s));
let node = self.lower_pat_ident(p, binding_mode, ident, lower_sub);
node
}
PatKind::Lit(ref e) => hir::PatKind::Lit(self.lower_expr(e)),
PatKind::TupleStruct(ref path, ref pats) => {
let qpath = self.lower_qpath(
p.id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct");
hir::PatKind::TupleStruct(qpath, pats, ddpos)
}
PatKind::Or(ref pats) => {
hir::PatKind::Or(self.arena.alloc_from_iter(pats.iter().map(|x| self.lower_pat(x))))
}
PatKind::Path(ref qself, ref path) => {
let qpath = self.lower_qpath(
p.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
hir::PatKind::Path(qpath)
}
PatKind::Struct(ref path, ref fields, etc) => {
let qpath = self.lower_qpath(
p.id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
let fs = self.arena.alloc_from_iter(fields.iter().map(|f| hir::FieldPat {
hir_id: self.next_id(),
ident: f.ident,
pat: self.lower_pat(&f.pat),
is_shorthand: f.is_shorthand,
span: f.span,
}));
hir::PatKind::Struct(qpath, fs, etc)
}
PatKind::Tuple(ref pats) => {
let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");
hir::PatKind::Tuple(pats, ddpos)
}
PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
PatKind::Ref(ref inner, mutbl) => hir::PatKind::Ref(self.lower_pat(inner), mutbl),
PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range(
self.lower_expr(e1),
self.lower_expr(e2),
self.lower_range_end(end),
),
PatKind::Slice(ref pats) => self.lower_pat_slice(pats),
PatKind::Rest => {
// If we reach here the `..` pattern is not semantically allowed.
self.ban_illegal_rest_pat(p.span)
}
PatKind::Paren(ref inner) => return self.lower_pat(inner),
PatKind::Mac(_) => panic!("Shouldn't exist here"),
};
self.pat_with_node_id_of(p, node)
}
fn lower_pat_tuple(
&mut self,
pats: &[P<Pat>],
ctx: &str,
) -> (&'hir [&'hir hir::Pat<'hir>], Option<usize>) {
let mut elems = Vec::with_capacity(pats.len());
let mut rest = None;
let mut iter = pats.iter().enumerate();
for (idx, pat) in iter.by_ref() {
// Interpret the first `..` pattern as a sub-tuple pattern.
// Note that unlike for slice patterns,
// where `xs @ ..` is a legal sub-slice pattern,
// it is not a legal sub-tuple pattern.
if pat.is_rest() {
rest = Some((idx, pat.span));
break;
}
// It was not a sub-tuple pattern so lower it normally.
elems.push(self.lower_pat(pat));
}
for (_, pat) in iter {
// There was a previous sub-tuple pattern; make sure we don't allow more...
if pat.is_rest() {
// ...but there was one again, so error.
self.ban_extra_rest_pat(pat.span, rest.unwrap().1, ctx);
} else {
elems.push(self.lower_pat(pat));
}
}
(self.arena.alloc_from_iter(elems), rest.map(|(ddpos, _)| ddpos))
}
/// Lower a slice pattern of form `[pat_0, ..., pat_n]` into
/// `hir::PatKind::Slice(before, slice, after)`.
///
/// When encountering `($binding_mode $ident @)? ..` (`slice`),
/// this is interpreted as a sub-slice pattern semantically.
/// Patterns that follow, which are not like `slice` -- or an error occurs, are in `after`.
fn lower_pat_slice(&mut self, pats: &[P<Pat>]) -> hir::PatKind<'hir> {
let mut before = Vec::new();
let mut after = Vec::new();
let mut slice = None;
let mut prev_rest_span = None;
let mut iter = pats.iter();
// Lower all the patterns until the first occurence of a sub-slice pattern.
for pat in iter.by_ref() {
match pat.kind {
// Found a sub-slice pattern `..`. Record, lower it to `_`, and stop here.
PatKind::Rest => {
prev_rest_span = Some(pat.span);
slice = Some(self.pat_wild_with_node_id_of(pat));
break;
}
// Found a sub-slice pattern `$binding_mode $ident @ ..`.
// Record, lower it to `$binding_mode $ident @ _`, and stop here.
PatKind::Ident(ref bm, ident, Some(ref sub)) if sub.is_rest() => {
prev_rest_span = Some(sub.span);
let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub));
let node = self.lower_pat_ident(pat, bm, ident, lower_sub);
slice = Some(self.pat_with_node_id_of(pat, node));
break;
}
// It was not a subslice pattern so lower it normally.
_ => before.push(self.lower_pat(pat)),
}
}
// Lower all the patterns after the first sub-slice pattern.
for pat in iter {
// There was a previous subslice pattern; make sure we don't allow more.
let rest_span = match pat.kind {
PatKind::Rest => Some(pat.span),
PatKind::Ident(.., Some(ref sub)) if sub.is_rest() => {
// The `HirValidator` is merciless; add a `_` pattern to avoid ICEs.
after.push(self.pat_wild_with_node_id_of(pat));
Some(sub.span)
}
_ => None,
};
if let Some(rest_span) = rest_span {
// We have e.g., `[a, .., b, ..]`. That's no good, error!
self.ban_extra_rest_pat(rest_span, prev_rest_span.unwrap(), "slice");
} else {
// Lower the pattern normally.
after.push(self.lower_pat(pat));
}
}
hir::PatKind::Slice(
self.arena.alloc_from_iter(before),
slice,
self.arena.alloc_from_iter(after),
)
}
fn lower_pat_ident(
&mut self,
p: &Pat,
binding_mode: &BindingMode,
ident: Ident,
lower_sub: impl FnOnce(&mut Self) -> Option<&'hir hir::Pat<'hir>>,
) -> hir::PatKind<'hir> {
match self.resolver.get_partial_res(p.id).map(|d| d.base_res()) {
// `None` can occur in body-less function signatures
res @ None | res @ Some(Res::Local(_)) => {
let canonical_id = match res {
Some(Res::Local(id)) => id,
_ => p.id,
};
hir::PatKind::Binding(
self.lower_binding_mode(binding_mode),
self.lower_node_id(canonical_id),
ident,
lower_sub(self),
)
}
Some(res) => hir::PatKind::Path(hir::QPath::Resolved(
None,
self.arena.alloc(hir::Path {
span: ident.span,
res: self.lower_res(res),
segments: arena_vec![self; hir::PathSegment::from_ident(ident)],
}),
)),
}
}
fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> {
self.pat_with_node_id_of(p, hir::PatKind::Wild)
}
/// Construct a `Pat` with the `HirId` of `p.id` lowered.
fn pat_with_node_id_of(&mut self, p: &Pat, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> {
self.arena.alloc(hir::Pat { hir_id: self.lower_node_id(p.id), kind, span: p.span })
}
/// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern.
fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) {
self.diagnostic()
.struct_span_err(sp, &format!("`..` can only be used once per {} pattern", ctx))
.span_label(sp, &format!("can only be used once per {} pattern", ctx))
.span_label(prev_sp, "previously used here")
.emit();
}
/// Used to ban the `..` pattern in places it shouldn't be semantically.
fn ban_illegal_rest_pat(&self, sp: Span) -> hir::PatKind<'hir> {
self.diagnostic()
.struct_span_err(sp, "`..` patterns are not allowed here")
.note("only allowed in tuple, tuple struct, and slice patterns")
.emit();
// We're not in a list context so `..` can be reasonably treated
// as `_` because it should always be valid and roughly matches the
// intent of `..` (notice that the rest of a single slot is that slot).
hir::PatKind::Wild
}
fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd {
match *e {
RangeEnd::Included(_) => hir::RangeEnd::Included,
RangeEnd::Excluded => hir::RangeEnd::Excluded,
}
}
}