Parse and recover from type ascription in patterns

5 files changed, 164 insertions, 39 deletions

diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 16d5edfd303..cd9d85b1d91 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -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.
@@ -2488,8 +2504,8 @@ 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,
@@ -2497,13 +2513,24 @@ impl<'a> Parser<'a> {
                         } 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
diff --git a/tests/ui/parser/issues/issue-87086-colon-path-sep.rs b/tests/ui/parser/issues/issue-87086-colon-path-sep.rs
index 0b7b67496d6..e1ea38f2795 100644
--- a/tests/ui/parser/issues/issue-87086-colon-path-sep.rs
+++ b/tests/ui/parser/issues/issue-87086-colon-path-sep.rs
@@ -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 => {}
diff --git a/tests/ui/parser/issues/issue-87086-colon-path-sep.stderr b/tests/ui/parser/issues/issue-87086-colon-path-sep.stderr
index 2050a16beb3..63b072ac4cd 100644
--- a/tests/ui/parser/issues/issue-87086-colon-path-sep.stderr
+++ b/tests/ui/parser/issues/issue-87086-colon-path-sep.stderr
@@ -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`.
diff --git a/tests/ui/parser/type-ascription-in-pattern.rs b/tests/ui/parser/type-ascription-in-pattern.rs
new file mode 100644
index 00000000000..fec168afba1
--- /dev/null
+++ b/tests/ui/parser/type-ascription-in-pattern.rs
@@ -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
+    }
+}
diff --git a/tests/ui/parser/type-ascription-in-pattern.stderr b/tests/ui/parser/type-ascription-in-pattern.stderr
new file mode 100644
index 00000000000..09190754993
--- /dev/null
+++ b/tests/ui/parser/type-ascription-in-pattern.stderr
@@ -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`.