bjoernager/rust
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Auto merge of #88672 - camelid:inc-parser-sugg, r=davidtwco

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Suggest `i += 1` when we see `i++` or `++i`

Closes #83502 (for `i++` and `++i`; `--i` should be covered by #82987, and `i--`
is tricky to handle).

This is a continuation of #83536.

r? `@estebank`
This commit is contained in:
bors 2022-04-03 05:24:20 +00:00
commit 133859d680
7 changed files with 514 additions and 1 deletions
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214
compiler/rustc_parse/src/parser/diagnostics.rs
View file

@ -17,7 +17,7 @@ use rustc_ast::{
};
use rustc_ast_pretty::pprust;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{pluralize, struct_span_err, Diagnostic, ErrorGuaranteed};
use rustc_errors::{pluralize, struct_span_err, Diagnostic, EmissionGuarantee, ErrorGuaranteed};
use rustc_errors::{Applicability, DiagnosticBuilder, Handler, PResult};
use rustc_span::source_map::Spanned;
use rustc_span::symbol::{kw, Ident};
@ -156,6 +156,89 @@ impl AttemptLocalParseRecovery {
}
}
/// Information for emitting suggestions and recovering from
/// C-style `i++`, `--i`, etc.
#[derive(Debug, Copy, Clone)]
struct IncDecRecovery {
/// Is this increment/decrement its own statement?
standalone: IsStandalone,
/// Is this an increment or decrement?
op: IncOrDec,
/// Is this pre- or postfix?
fixity: UnaryFixity,
}
/// Is an increment or decrement expression its own statement?
#[derive(Debug, Copy, Clone)]
enum IsStandalone {
/// It's standalone, i.e., its own statement.
Standalone,
/// It's a subexpression, i.e., *not* standalone.
Subexpr,
/// It's maybe standalone; we're not sure.
Maybe,
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum IncOrDec {
Inc,
// FIXME: `i--` recovery isn't implemented yet
#[allow(dead_code)]
Dec,
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum UnaryFixity {
Pre,
Post,
}
impl IncOrDec {
fn chr(&self) -> char {
match self {
Self::Inc => '+',
Self::Dec => '-',
}
}
fn name(&self) -> &'static str {
match self {
Self::Inc => "increment",
Self::Dec => "decrement",
}
}
}
impl std::fmt::Display for UnaryFixity {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Self::Pre => write!(f, "prefix"),
Self::Post => write!(f, "postfix"),
}
}
}
struct MultiSugg {
msg: String,
patches: Vec<(Span, String)>,
applicability: Applicability,
}
impl MultiSugg {
fn emit<G: EmissionGuarantee>(self, err: &mut DiagnosticBuilder<'_, G>) {
err.multipart_suggestion(&self.msg, self.patches, self.applicability);
}
/// Overrides individual messages and applicabilities.
fn emit_many<G: EmissionGuarantee>(
err: &mut DiagnosticBuilder<'_, G>,
msg: &str,
applicability: Applicability,
suggestions: impl Iterator<Item = Self>,
) {
err.multipart_suggestions(msg, suggestions.map(|s| s.patches), applicability);
}
}
// SnapshotParser is used to create a snapshot of the parser
// without causing duplicate errors being emitted when the `Parser`
// is dropped.
@ -1171,6 +1254,135 @@ impl<'a> Parser<'a> {
Ok(())
}
pub(super) fn recover_from_prefix_increment(
&mut self,
operand_expr: P<Expr>,
op_span: Span,
prev_is_semi: bool,
) -> PResult<'a, P<Expr>> {
let standalone =
if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr };
let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
self.recover_from_inc_dec(operand_expr, kind, op_span)
}
pub(super) fn recover_from_postfix_increment(
&mut self,
operand_expr: P<Expr>,
op_span: Span,
) -> PResult<'a, P<Expr>> {
let kind = IncDecRecovery {
standalone: IsStandalone::Maybe,
op: IncOrDec::Inc,
fixity: UnaryFixity::Post,
};
self.recover_from_inc_dec(operand_expr, kind, op_span)
}
fn recover_from_inc_dec(
&mut self,
base: P<Expr>,
kind: IncDecRecovery,
op_span: Span,
) -> PResult<'a, P<Expr>> {
let mut err = self.struct_span_err(
op_span,
&format!("Rust has no {} {} operator", kind.fixity, kind.op.name()),
);
err.span_label(op_span, &format!("not a valid {} operator", kind.fixity));
let help_base_case = |mut err: DiagnosticBuilder<'_, _>, base| {
err.help(&format!("use `{}= 1` instead", kind.op.chr()));
err.emit();
Ok(base)
};
// (pre, post)
let spans = match kind.fixity {
UnaryFixity::Pre => (op_span, base.span.shrink_to_hi()),
UnaryFixity::Post => (base.span.shrink_to_lo(), op_span),
};
match kind.standalone {
IsStandalone::Standalone => self.inc_dec_standalone_suggest(kind, spans).emit(&mut err),
IsStandalone::Subexpr => {
let Ok(base_src) = self.span_to_snippet(base.span)
else { return help_base_case(err, base) };
match kind.fixity {
UnaryFixity::Pre => {
self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
}
UnaryFixity::Post => {
self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
}
}
}
IsStandalone::Maybe => {
let Ok(base_src) = self.span_to_snippet(base.span)
else { return help_base_case(err, base) };
let sugg1 = match kind.fixity {
UnaryFixity::Pre => self.prefix_inc_dec_suggest(base_src, kind, spans),
UnaryFixity::Post => self.postfix_inc_dec_suggest(base_src, kind, spans),
};
let sugg2 = self.inc_dec_standalone_suggest(kind, spans);
MultiSugg::emit_many(
&mut err,
"use `+= 1` instead",
Applicability::Unspecified,
[sugg1, sugg2].into_iter(),
)
}
}
Err(err)
}
fn prefix_inc_dec_suggest(
&mut self,
base_src: String,
kind: IncDecRecovery,
(pre_span, post_span): (Span, Span),
) -> MultiSugg {
MultiSugg {
msg: format!("use `{}= 1` instead", kind.op.chr()),
patches: vec![
(pre_span, "{ ".to_string()),
(post_span, format!(" {}= 1; {} }}", kind.op.chr(), base_src)),
],
applicability: Applicability::MachineApplicable,
}
}
fn postfix_inc_dec_suggest(
&mut self,
base_src: String,
kind: IncDecRecovery,
(pre_span, post_span): (Span, Span),
) -> MultiSugg {
let tmp_var = if base_src.trim() == "tmp" { "tmp_" } else { "tmp" };
MultiSugg {
msg: format!("use `{}= 1` instead", kind.op.chr()),
patches: vec![
(pre_span, format!("{{ let {} = ", tmp_var)),
(post_span, format!("; {} {}= 1; {} }}", base_src, kind.op.chr(), tmp_var)),
],
applicability: Applicability::HasPlaceholders,
}
}
fn inc_dec_standalone_suggest(
&mut self,
kind: IncDecRecovery,
(pre_span, post_span): (Span, Span),
) -> MultiSugg {
MultiSugg {
msg: format!("use `{}= 1` instead", kind.op.chr()),
patches: vec![(pre_span, String::new()), (post_span, format!(" {}= 1", kind.op.chr()))],
applicability: Applicability::MachineApplicable,
}
}
/// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
/// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
/// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.

24
compiler/rustc_parse/src/parser/expr.rs
View file

@ -267,6 +267,17 @@ impl<'a> Parser<'a> {
self.bump();
}
if self.prev_token == token::BinOp(token::Plus)
&& self.token == token::BinOp(token::Plus)
&& self.prev_token.span.between(self.token.span).is_empty()
{
let op_span = self.prev_token.span.to(self.token.span);
// Eat the second `+`
self.bump();
lhs = self.recover_from_postfix_increment(lhs, op_span)?;
continue;
}
let op = op.node;
// Special cases:
if op == AssocOp::As {
@ -580,6 +591,19 @@ impl<'a> Parser<'a> {
this.bump();
this.parse_prefix_expr(None)
} // `+expr`
// Recover from `++x`:
token::BinOp(token::Plus)
if this.look_ahead(1, |t| *t == token::BinOp(token::Plus)) =>
{
let prev_is_semi = this.prev_token == token::Semi;
let pre_span = this.token.span.to(this.look_ahead(1, |t| t.span));
// Eat both `+`s.
this.bump();
this.bump();
let operand_expr = this.parse_dot_or_call_expr(Default::default())?;
this.recover_from_prefix_increment(operand_expr, pre_span, prev_is_semi)
}
token::Ident(..) if this.token.is_keyword(kw::Box) => {
make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
}