Only suggest turbofish in patterns if we may recover

fmease · fmease · commit 3ed77e98fa9e · 2023-09-12T16:38:59.000+02:00
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
@@ -830,7 +830,8 @@ impl<'a> Parser<'a> {
     ) -> PResult<'a, PatKind> {
         let ident = self.parse_ident()?;
 
-        if !matches!(syntax_loc, Some(PatternLocation::FunctionParameter))
+        if self.may_recover()
+            && !matches!(syntax_loc, Some(PatternLocation::FunctionParameter))
             && self.check_noexpect(&token::Lt)
             && self.look_ahead(1, |t| t.can_begin_type())
         {
diff --git a/tests/ui/parser/issues/issue-115780-pat-lt-bracket-in-macro-call.rs b/tests/ui/parser/issues/issue-115780-pat-lt-bracket-in-macro-call.rs
@@ -0,0 +1,21 @@
+// Regression test for issue #115780.
+// Ensure that we don't emit a parse error for the token sequence `Ident "<" Ty` in pattern position
+// if we are inside a macro call since it can be valid input for a subsequent macro rule.
+// See also #103534.
+
+// check-pass
+
+macro_rules! mdo {
+    ($p: pat =<< $e: expr ; $( $t: tt )*) => {
+        $e.and_then(|$p| mdo! { $( $t )* })
+    };
+    (ret<$ty: ty> $e: expr;) => { Some::<$ty>($e) };
+}
+
+fn main() {
+    mdo! {
+        x_val =<< Some(0);
+        y_val =<< Some(1);
+        ret<(i32, i32)> (x_val, y_val);
+    };
+}

Original file line number	Diff line number	Diff line change
`@@ -830,7 +830,8 @@ impl<'a> Parser<'a> {`
`830`	`830`	`) -> PResult<'a, PatKind> {`
`831`	`831`	`let ident = self.parse_ident()?;`
`832`	`832`
`833`		`- if !matches!(syntax_loc, Some(PatternLocation::FunctionParameter))`
	`833`	`+ if self.may_recover()`
	`834`	`+ && !matches!(syntax_loc, Some(PatternLocation::FunctionParameter))`
`834`	`835`	`&& self.check_noexpect(&token::Lt)`
`835`	`836`	`&& self.look_ahead(1, \|t\| t.can_begin_type())`
`836`	`837`	`{`