Fix ICE on invalid variable declarations in macro calls

compiler/rustc_parse/src/parser/stmt.rs

@@ -72,14 +72,22 @@ impl<'a> Parser<'a> {
 
         Ok(Some(if self.token.is_keyword(kw::Let) {
             self.parse_local_mk(lo, attrs, capture_semi, force_collect)?
-        } else if self.is_kw_followed_by_ident(kw::Mut) {
-            self.recover_stmt_local(lo, attrs, InvalidVariableDeclarationSub::MissingLet)?
-        } else if self.is_kw_followed_by_ident(kw::Auto) {
+        } else if self.is_kw_followed_by_ident(kw::Mut) && self.may_recover() {
+            self.recover_stmt_local_after_let(lo, attrs, InvalidVariableDeclarationSub::MissingLet)?
+        } else if self.is_kw_followed_by_ident(kw::Auto) && self.may_recover() {
             self.bump(); // `auto`
-            self.recover_stmt_local(lo, attrs, InvalidVariableDeclarationSub::UseLetNotAuto)?
-        } else if self.is_kw_followed_by_ident(sym::var) {
+            self.recover_stmt_local_after_let(
+                lo,
+                attrs,
+                InvalidVariableDeclarationSub::UseLetNotAuto,
+            )?
+        } else if self.is_kw_followed_by_ident(sym::var) && self.may_recover() {
             self.bump(); // `var`
-            self.recover_stmt_local(lo, attrs, InvalidVariableDeclarationSub::UseLetNotVar)?
+            self.recover_stmt_local_after_let(
+                lo,
+                attrs,
+                InvalidVariableDeclarationSub::UseLetNotVar,
+            )?
         } else if self.check_path() && !self.token.is_qpath_start() && !self.is_path_start_item() {
             // We have avoided contextual keywords like `union`, items with `crate` visibility,
             // or `auto trait` items. We aim to parse an arbitrary path `a::b` but not something
@@ -213,13 +221,21 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn recover_stmt_local(
+    fn recover_stmt_local_after_let(
         &mut self,
         lo: Span,
         attrs: AttrWrapper,
         subdiagnostic: fn(Span) -> InvalidVariableDeclarationSub,
     ) -> PResult<'a, Stmt> {
-        let stmt = self.recover_local_after_let(lo, attrs)?;
+        let stmt =
+            self.collect_tokens_trailing_token(attrs, ForceCollect::Yes, |this, attrs| {
+                let local = this.parse_local(attrs)?;
+                // FIXME - maybe capture semicolon in recovery?
+                Ok((
+                    this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)),
+                    TrailingToken::None,
+                ))
+            })?;
         self.sess.emit_err(InvalidVariableDeclaration { span: lo, sub: subdiagnostic(lo) });
         Ok(stmt)
     }
@@ -243,17 +259,6 @@ impl<'a> Parser<'a> {
         })
     }
 
-    fn recover_local_after_let(&mut self, lo: Span, attrs: AttrWrapper) -> PResult<'a, Stmt> {
-        self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
-            let local = this.parse_local(attrs)?;
-            // FIXME - maybe capture semicolon in recovery?
-            Ok((
-                this.mk_stmt(lo.to(this.prev_token.span), StmtKind::Local(local)),
-                TrailingToken::None,
-            ))
-        })
-    }
-
     /// Parses a local variable declaration.
     fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> {
         let lo = self.prev_token.span;

src/test/ui/macros/issue-103529.rs

@@ -0,0 +1,13 @@
+macro_rules! m {
+    ($s:stmt) => {}
+}
+
+m! { mut x }
+//~^ ERROR expected expression, found keyword `mut`
+//~| ERROR expected a statement
+m! { auto x }
+//~^ ERROR invalid variable declaration
+m! { var x }
+//~^ ERROR invalid variable declaration
+
+fn main() {}

src/test/ui/macros/issue-103529.stderr

@@ -0,0 +1,39 @@
+error: expected expression, found keyword `mut`
+  --> $DIR/issue-103529.rs:5:6
+   |
+LL | m! { mut x }
+   |      ^^^ expected expression
+
+error: expected a statement
+  --> $DIR/issue-103529.rs:5:10
+   |
+LL |     ($s:stmt) => {}
+   |      ------- while parsing argument for this `stmt` macro fragment
+...
+LL | m! { mut x }
+   |          ^
+
+error: invalid variable declaration
+  --> $DIR/issue-103529.rs:8:6
+   |
+LL | m! { auto x }
+   |      ^^^^
+   |
+help: write `let` instead of `auto` to introduce a new variable
+   |
+LL | m! { let x }
+   |      ~~~
+
+error: invalid variable declaration
+  --> $DIR/issue-103529.rs:10:6
+   |
+LL | m! { var x }
+   |      ^^^
+   |
+help: write `let` instead of `var` to introduce a new variable
+   |
+LL | m! { let x }
+   |      ~~~
+
+error: aborting due to 4 previous errors
+