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Suggest a path separator if a stray colon is found in a match arm

Browse source 
Co-authored-by: Esteban Kuber <estebank@users.noreply.github.com>
This commit is contained in:
Fabian Wolff 2021-07-13 13:18:03 +02:00
parent 394804bb23
commit 2362450425
7 changed files with 219 additions and 19 deletions
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12
compiler/rustc_expand/src/expand.rs
View file

@ -22,7 +22,9 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_data_structures::sync::Lrc;
use rustc_errors::{Applicability, FatalError, PResult};
use rustc_feature::Features;
use rustc_parse::parser::{AttemptLocalParseRecovery, ForceCollect, Parser, RecoverComma};
use rustc_parse::parser::{
AttemptLocalParseRecovery, ForceCollect, Parser, RecoverColon, RecoverComma,
};
use rustc_parse::validate_attr;
use rustc_session::lint::builtin::UNUSED_DOC_COMMENTS;
use rustc_session::lint::BuiltinLintDiagnostics;
@ -930,9 +932,11 @@ pub fn parse_ast_fragment<'a>(
}
}
AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
AstFragmentKind::Pat => {
AstFragment::Pat(this.parse_pat_allow_top_alt(None, RecoverComma::No)?)
}
AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat_allow_top_alt(
None,
RecoverComma::No,
RecoverColon::Yes,
)?),
AstFragmentKind::Arms
| AstFragmentKind::Fields
| AstFragmentKind::FieldPats

8
compiler/rustc_parse/src/parser/expr.rs
View file

@ -1,4 +1,4 @@
use super::pat::{RecoverComma, PARAM_EXPECTED};
use super::pat::{RecoverColon, RecoverComma, PARAM_EXPECTED};
use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
use super::{AttrWrapper, BlockMode, ForceCollect, Parser, PathStyle, Restrictions, TokenType};
use super::{SemiColonMode, SeqSep, TokenExpectType, TrailingToken};
@ -1813,7 +1813,7 @@ impl<'a> Parser<'a> {
/// The `let` token has already been eaten.
fn parse_let_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
let lo = self.prev_token.span;
let pat = self.parse_pat_allow_top_alt(None, RecoverComma::Yes)?;
let pat = self.parse_pat_allow_top_alt(None, RecoverComma::Yes, RecoverColon::Yes)?;
self.expect(&token::Eq)?;
let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
@ -1876,7 +1876,7 @@ impl<'a> Parser<'a> {
_ => None,
};
let pat = self.parse_pat_allow_top_alt(None, RecoverComma::Yes)?;
let pat = self.parse_pat_allow_top_alt(None, RecoverComma::Yes, RecoverColon::Yes)?;
if !self.eat_keyword(kw::In) {
self.error_missing_in_for_loop();
}
@ -2083,7 +2083,7 @@ impl<'a> Parser<'a> {
let attrs = self.parse_outer_attributes()?;
self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
let lo = this.token.span;
let pat = this.parse_pat_allow_top_alt(None, RecoverComma::Yes)?;
let pat = this.parse_pat_allow_top_alt(None, RecoverComma::Yes, RecoverColon::Yes)?;
let guard = if this.eat_keyword(kw::If) {
let if_span = this.prev_token.span;
let cond = this.parse_expr()?;

2
compiler/rustc_parse/src/parser/mod.rs
View file

@ -14,7 +14,7 @@ use crate::lexer::UnmatchedBrace;
pub use attr_wrapper::AttrWrapper;
pub use diagnostics::AttemptLocalParseRecovery;
use diagnostics::Error;
pub use pat::RecoverComma;
pub use pat::{RecoverColon, RecoverComma};
pub use path::PathStyle;
use rustc_ast::ptr::P;

4
compiler/rustc_parse/src/parser/nonterminal.rs
View file

@ -5,7 +5,7 @@ use rustc_ast_pretty::pprust;
use rustc_errors::PResult;
use rustc_span::symbol::{kw, Ident};
use crate::parser::pat::RecoverComma;
use crate::parser::pat::{RecoverColon, RecoverComma};
use crate::parser::{FollowedByType, ForceCollect, Parser, PathStyle};
impl<'a> Parser<'a> {
@ -125,7 +125,7 @@ impl<'a> Parser<'a> {
token::NtPat(self.collect_tokens_no_attrs(|this| match kind {
NonterminalKind::PatParam { .. } => this.parse_pat_no_top_alt(None),
NonterminalKind::PatWithOr { .. } => {
this.parse_pat_allow_top_alt(None, RecoverComma::No)
this.parse_pat_allow_top_alt(None, RecoverComma::No, RecoverColon::No)
}
_ => unreachable!(),
})?)

78
compiler/rustc_parse/src/parser/pat.rs
View file

@ -24,6 +24,13 @@ pub enum RecoverComma {
No,
}
/// Whether or not to recover a `:` when parsing patterns that were meant to be paths.
#[derive(PartialEq, Copy, Clone)]
pub enum RecoverColon {
Yes,
No,
}
/// The result of `eat_or_separator`. We want to distinguish which case we are in to avoid
/// emitting duplicate diagnostics.
#[derive(Debug, Clone, Copy)]
@ -58,8 +65,9 @@ impl<'a> Parser<'a> {
&mut self,
expected: Expected,
rc: RecoverComma,
ra: RecoverColon,
) -> PResult<'a, P<Pat>> {
self.parse_pat_allow_top_alt_inner(expected, rc).map(|(pat, _)| pat)
self.parse_pat_allow_top_alt_inner(expected, rc, ra).map(|(pat, _)| pat)
}
/// Returns the pattern and a bool indicating whether we recovered from a trailing vert (true =
@ -68,6 +76,7 @@ impl<'a> Parser<'a> {
&mut self,
expected: Expected,
rc: RecoverComma,
ra: RecoverColon,
) -> PResult<'a, (P<Pat>, bool)> {
// Keep track of whether we recovered from a trailing vert so that we can avoid duplicated
// suggestions (which bothers rustfix).
@ -89,6 +98,56 @@ impl<'a> Parser<'a> {
// If we parsed a leading `|` which should be gated,
// then we should really gate the leading `|`.
// This complicated procedure is done purely for diagnostics UX.
let mut first_pat = first_pat;
if let (RecoverColon::Yes, token::Colon) = (ra, &self.token.kind) {
if matches!(
first_pat.kind,
PatKind::Ident(BindingMode::ByValue(Mutability::Not), _, None)
| PatKind::Path(..)
) && self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
{
// The pattern looks like it might be a path with a `::` -> `:` typo:
// `match foo { bar:baz => {} }`
let span = self.token.span;
// We only emit "unexpected `:`" error here if we can successfully parse the
// whole pattern correctly in that case.
let snapshot = self.clone();
// Create error for "unexpected `:`".
match self.expected_one_of_not_found(&[], &[]) {
Err(mut err) => {
self.bump(); // Skip the `:`.
match self.parse_pat_no_top_alt(expected) {
Err(mut inner_err) => {
// Carry on as if we had not done anything, callers will emit a
// reasonable error.
inner_err.cancel();
err.cancel();
*self = snapshot;
}
Ok(pat) => {
// We've parsed the rest of the pattern.
err.span_suggestion(
span,
"maybe write a path separator here",
"::".to_string(),
Applicability::MachineApplicable,
);
err.emit();
first_pat =
self.mk_pat(first_pat.span.to(pat.span), PatKind::Wild);
}
}
}
_ => {
// Carry on as if we had not done anything. This should be unreachable.
*self = snapshot;
}
};
}
}
if let Some(leading_vert_span) = leading_vert_span {
// If there was a leading vert, treat this as an or-pattern. This improves
// diagnostics.
@ -140,7 +199,8 @@ impl<'a> Parser<'a> {
// We use `parse_pat_allow_top_alt` regardless of whether we actually want top-level
// or-patterns so that we can detect when a user tries to use it. This allows us to print a
// better error message.
let (pat, trailing_vert) = self.parse_pat_allow_top_alt_inner(expected, rc)?;
let (pat, trailing_vert) =
self.parse_pat_allow_top_alt_inner(expected, rc, RecoverColon::No)?;
let colon = self.eat(&token::Colon);
if let PatKind::Or(pats) = &pat.kind {
@ -350,7 +410,7 @@ impl<'a> Parser<'a> {
} else if self.check(&token::OpenDelim(token::Bracket)) {
// Parse `[pat, pat,...]` as a slice pattern.
let (pats, _) = self.parse_delim_comma_seq(token::Bracket, |p| {
p.parse_pat_allow_top_alt(None, RecoverComma::No)
p.parse_pat_allow_top_alt(None, RecoverComma::No, RecoverColon::No)
})?;
PatKind::Slice(pats)
} else if self.check(&token::DotDot) && !self.is_pat_range_end_start(1) {
@ -563,8 +623,9 @@ impl<'a> Parser<'a> {
/// Parse a tuple or parenthesis pattern.
fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> {
let (fields, trailing_comma) =
self.parse_paren_comma_seq(|p| p.parse_pat_allow_top_alt(None, RecoverComma::No))?;
let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| {
p.parse_pat_allow_top_alt(None, RecoverComma::No, RecoverColon::No)
})?;
// Here, `(pat,)` is a tuple pattern.
// For backward compatibility, `(..)` is a tuple pattern as well.
@ -873,8 +934,9 @@ impl<'a> Parser<'a> {
/// Parse tuple struct or tuple variant pattern (e.g. `Foo(...)` or `Foo::Bar(...)`).
fn parse_pat_tuple_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
let (fields, _) =
self.parse_paren_comma_seq(|p| p.parse_pat_allow_top_alt(None, RecoverComma::No))?;
let (fields, _) = self.parse_paren_comma_seq(|p| {
p.parse_pat_allow_top_alt(None, RecoverComma::No, RecoverColon::No)
})?;
if qself.is_some() {
self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
}
@ -1033,7 +1095,7 @@ impl<'a> Parser<'a> {
// Parsing a pattern of the form `fieldname: pat`.
let fieldname = self.parse_field_name()?;
self.bump();
let pat = self.parse_pat_allow_top_alt(None, RecoverComma::No)?;
let pat = self.parse_pat_allow_top_alt(None, RecoverComma::No, RecoverColon::No)?;
hi = pat.span;
(pat, fieldname, false)
} else {

66
src/test/ui/parser/issue-87086-colon-path-sep.rs Normal file
View file

@ -0,0 +1,66 @@
// Tests that a suggestion is issued if the user wrote a colon instead of
// a path separator in a match arm.
enum Foo {
Bar,
Baz,
}
fn f() -> Foo { Foo::Bar }
fn g1() {
match f() {
Foo:Bar => {}
//~^ ERROR: expected one of
//~| HELP: maybe write a path separator here
_ => {}
}
match f() {
Foo::Bar:Baz => {}
//~^ ERROR: expected one of
//~| HELP: maybe write a path separator here
_ => {}
}
match f() {
Foo:Bar::Baz => {}
//~^ ERROR: expected one of
//~| HELP: maybe write a path separator here
_ => {}
}
match f() {
Foo: Bar::Baz if true => {}
//~^ ERROR: expected one of
//~| HELP: maybe write a path separator here
_ => {}
}
if let Bar:Baz = f() {
//~^ ERROR: expected one of
//~| HELP: maybe write a path separator here
}
}
fn g1_neg() {
match f() {
ref Foo: Bar::Baz => {}
//~^ ERROR: expected one of
_ => {}
}
}
fn g2_neg() {
match f() {
mut Foo: Bar::Baz => {}
//~^ ERROR: expected one of
_ => {}
}
}
fn main() {
let myfoo = Foo::Bar;
match myfoo {
Foo::Bar => {}
Foo:Bar::Baz => {}
//~^ ERROR: expected one of
//~| HELP: maybe write a path separator here
}
}

68
src/test/ui/parser/issue-87086-colon-path-sep.stderr Normal file
View file

@ -0,0 +1,68 @@
error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:13:12
|
LL | Foo:Bar => {}
| ^
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `{`, or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:19:17
|
LL | Foo::Bar:Baz => {}
| ^
| |
| expected one of 8 possible tokens
| help: maybe write a path separator here: `::`
error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:25:12
|
LL | Foo:Bar::Baz => {}
| ^
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:31:12
|
LL | Foo: Bar::Baz if true => {}
| ^
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:36:15
|
LL | if let Bar:Baz = f() {
| ^
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
error: expected one of `=>`, `@`, `if`, or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:44:16
|
LL | ref Foo: Bar::Baz => {}
| ^ expected one of `=>`, `@`, `if`, or `|`
error: expected one of `=>`, `@`, `if`, or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:52:16
|
LL | mut Foo: Bar::Baz => {}
| ^ expected one of `=>`, `@`, `if`, or `|`
error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:62:12
|
LL | Foo:Bar::Baz => {}
| ^
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
error: aborting due to 8 previous errors