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Feb 3, 2023
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Parse and recover from type ascription in patterns #107602

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51 changes: 39 additions & 12 deletions compiler/rustc_parse/src/parser/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2405,26 +2405,42 @@ impl<'a> Parser<'a> {
if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
|| !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
{
let mut snapshot_type = self.create_snapshot_for_diagnostic();
snapshot_type.bump(); // `:`
match snapshot_type.parse_ty() {
Err(inner_err) => {
inner_err.cancel();
}
Ok(ty) => {
let Err(mut err) = self.expected_one_of_not_found(&[], &[]) else {
return first_pat;
};
err.span_label(ty.span, "specifying the type of a pattern isn't supported");
self.restore_snapshot(snapshot_type);
let span = first_pat.span.to(ty.span);
first_pat = self.mk_pat(span, PatKind::Wild);
err.emit();
}
}
return first_pat;
}
// The pattern looks like it might be a path with a `::` -> `:` typo:
// `match foo { bar:baz => {} }`
let span = self.token.span;
let colon_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.create_snapshot_for_diagnostic();
let mut snapshot_pat = self.create_snapshot_for_diagnostic();
let mut snapshot_type = self.create_snapshot_for_diagnostic();

// 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) {
// Skip the `:`.
snapshot_pat.bump();
snapshot_type.bump();
match snapshot_pat.parse_pat_no_top_alt(expected) {
Err(inner_err) => {
// Carry on as if we had not done anything, callers will emit a
// reasonable error.
inner_err.cancel();
err.cancel();
self.restore_snapshot(snapshot);
}
Ok(mut pat) => {
// We've parsed the rest of the pattern.
Expand Down Expand Up @@ -2488,22 +2504,33 @@ impl<'a> Parser<'a> {
_ => {}
}
if show_sugg {
err.span_suggestion(
span,
err.span_suggestion_verbose(
colon_span.until(self.look_ahead(1, |t| t.span)),
"maybe write a path separator here",
"::",
Applicability::MaybeIncorrect,
);
} else {
first_pat = self.mk_pat(new_span, PatKind::Wild);
}
err.emit();
self.restore_snapshot(snapshot_pat);
}
}
match snapshot_type.parse_ty() {
Err(inner_err) => {
inner_err.cancel();
}
Ok(ty) => {
err.span_label(ty.span, "specifying the type of a pattern isn't supported");
self.restore_snapshot(snapshot_type);
let new_span = first_pat.span.to(ty.span);
first_pat = self.mk_pat(new_span, PatKind::Wild);
}
}
err.emit();
}
_ => {
// Carry on as if we had not done anything. This should be unreachable.
self.restore_snapshot(snapshot);
}
};
first_pat
Expand Down
1 change: 0 additions & 1 deletion tests/ui/parser/issues/issue-87086-colon-path-sep.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,6 @@ fn main() {
Foo:Bar::Baz => {}
//~^ ERROR: expected one of
//~| HELP: maybe write a path separator here
//~| ERROR: failed to resolve: `Bar` is a variant, not a module
}
match myfoo {
Foo::Bar => {}
Expand Down
81 changes: 55 additions & 26 deletions tests/ui/parser/issues/issue-87086-colon-path-sep.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -2,89 +2,118 @@ error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:17:12
|
LL | Foo:Bar => {}
| ^
| ^--- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
|
help: maybe write a path separator here
|
LL | Foo::Bar => {}
| ~~

error: expected one of `!`, `(`, `...`, `..=`, `..`, `::`, `{`, or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:23:17
|
LL | qux::Foo:Bar => {}
| ^
| ^--- specifying the type of a pattern isn't supported
| |
| expected one of 8 possible tokens
| help: maybe write a path separator here: `::`
|
help: maybe write a path separator here
|
LL | qux::Foo::Bar => {}
| ~~

error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:29:12
|
LL | qux:Foo::Baz => {}
| ^
| ^-------- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
|
help: maybe write a path separator here
|
LL | qux::Foo::Baz => {}
| ~~

error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:35:12
|
LL | qux: Foo::Baz if true => {}
| ^
| ^ -------- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
|
help: maybe write a path separator here
|
LL | qux::Foo::Baz if true => {}
| ~~

error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:40:15
|
LL | if let Foo:Bar = f() {
| ^
| ^--- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
|
help: maybe write a path separator here
|
LL | if let Foo::Bar = f() {
| ~~

error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:48:16
|
LL | ref qux: Foo::Baz => {}
| ^
| ^ -------- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
|
help: maybe write a path separator here
|
LL | ref qux::Foo::Baz => {}
| ~~

error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:57:16
|
LL | mut qux: Foo::Baz => {}
| ^
| ^ -------- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
|
help: maybe write a path separator here
|
LL | mut qux::Foo::Baz => {}
| ~~

error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:68:12
|
LL | Foo:Bar::Baz => {}
| ^
| ^-------- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`
|
help: maybe write a path separator here
|
LL | Foo::Bar::Baz => {}
| ~~

error: expected one of `@` or `|`, found `:`
--> $DIR/issue-87086-colon-path-sep.rs:75:12
--> $DIR/issue-87086-colon-path-sep.rs:74:12
|
LL | Foo:Bar => {}
| ^
| ^--- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
| help: maybe write a path separator here: `::`

error[E0433]: failed to resolve: `Bar` is a variant, not a module
--> $DIR/issue-87086-colon-path-sep.rs:68:13
|
LL | Foo:Bar::Baz => {}
| ^^^ `Bar` is a variant, not a module
help: maybe write a path separator here
|
LL | Foo::Bar => {}
| ~~

error: aborting due to 10 previous errors
error: aborting due to 9 previous errors

For more information about this error, try `rustc --explain E0433`.
16 changes: 16 additions & 0 deletions tests/ui/parser/type-ascription-in-pattern.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
fn foo(x: bool) -> i32 {
match x {
x: i32 => x, //~ ERROR expected
//~^ ERROR mismatched types
true => 42.,
false => 0.333,
}
}

fn main() {
match foo(true) {
42: i32 => (), //~ ERROR expected
_: f64 => (), //~ ERROR expected
x: i32 => (), //~ ERROR expected
}
}
54 changes: 54 additions & 0 deletions tests/ui/parser/type-ascription-in-pattern.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,54 @@
error: expected one of `@` or `|`, found `:`
--> $DIR/type-ascription-in-pattern.rs:3:10
|
LL | x: i32 => x,
| ^ --- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
|
help: maybe write a path separator here
|
LL | x::i32 => x,
| ~~

error: expected one of `...`, `..=`, `..`, or `|`, found `:`
--> $DIR/type-ascription-in-pattern.rs:12:11
|
LL | 42: i32 => (),
| ^ --- specifying the type of a pattern isn't supported
| |
| expected one of `...`, `..=`, `..`, or `|`

error: expected `|`, found `:`
--> $DIR/type-ascription-in-pattern.rs:13:10
|
LL | _: f64 => (),
| ^ --- specifying the type of a pattern isn't supported
| |
| expected `|`

error: expected one of `@` or `|`, found `:`
--> $DIR/type-ascription-in-pattern.rs:14:10
|
LL | x: i32 => (),
| ^ --- specifying the type of a pattern isn't supported
| |
| expected one of `@` or `|`
|
help: maybe write a path separator here
|
LL | x::i32 => (),
| ~~

error[E0308]: mismatched types
--> $DIR/type-ascription-in-pattern.rs:3:19
|
LL | fn foo(x: bool) -> i32 {
| --- expected `i32` because of return type
LL | match x {
LL | x: i32 => x,
| ^ expected `i32`, found `bool`

error: aborting due to 5 previous errors

For more information about this error, try `rustc --explain E0308`.