Properly parse legacy trait objects with leading ForType

Author: Veykril

crates/parser/src/grammar/type_params.rs

@@ -113,7 +113,7 @@ fn type_bound(p: &mut Parser) -> bool {
     p.eat(T![?]);
     match p.current() {
         LIFETIME_IDENT => lifetime(p),
-        T![for] => types::for_type(p),
+        T![for] => types::for_type(p, false),
         _ if paths::is_use_path_start(p) => types::path_type_(p, false),
         _ => {
             m.abandon(p);

crates/parser/src/grammar/types.rs

@@ -44,7 +44,7 @@ fn type_with_bounds_cond(p: &mut Parser, allow_bounds: bool) {
         T![&] => ref_type(p),
         T![_] => infer_type(p),
         T![fn] | T![unsafe] | T![extern] => fn_ptr_type(p),
-        T![for] => for_type(p),
+        T![for] => for_type(p, allow_bounds),
         T![impl] => impl_trait_type(p),
         T![dyn] => dyn_trait_type(p),
         // Some path types are not allowed to have bounds (no plus)
@@ -227,7 +227,7 @@ pub(super) fn for_binder(p: &mut Parser) {
 // type A = for<'a> fn() -> ();
 // type B = for<'a> unsafe extern "C" fn(&'a ()) -> ();
 // type Obj = for<'a> PartialEq<&'a i32>;
-pub(super) fn for_type(p: &mut Parser) {
+pub(super) fn for_type(p: &mut Parser, allow_bounds: bool) {
     assert!(p.at(T![for]));
     let m = p.start();
     for_binder(p);
@@ -240,7 +240,13 @@ pub(super) fn for_type(p: &mut Parser) {
         }
     }
     type_no_bounds(p);
-    m.complete(p, FOR_TYPE);
+    let completed = m.complete(p, FOR_TYPE);
+
+    // test no_dyn_trait_leading_for
+    // type A = for<'a> Test<'a> + Send;
+    if allow_bounds {
+        opt_type_bounds_as_dyn_trait_type(p, completed);
+    }
 }
 
 // test impl_trait_type
@@ -290,7 +296,7 @@ fn path_or_macro_type_(p: &mut Parser, allow_bounds: bool) {
     let path = m.complete(p, kind);
 
     if allow_bounds {
-        opt_path_type_bounds_as_dyn_trait_type(p, path);
+        opt_type_bounds_as_dyn_trait_type(p, path);
     }
 }
 
@@ -304,19 +310,23 @@ pub(super) fn path_type_(p: &mut Parser, allow_bounds: bool) {
     // fn foo() -> Box<dyn T + 'f> {}
     let path = m.complete(p, PATH_TYPE);
     if allow_bounds {
-        opt_path_type_bounds_as_dyn_trait_type(p, path);
+        opt_type_bounds_as_dyn_trait_type(p, path);
     }
 }
 
-/// This turns a parsed PATH_TYPE optionally into a DYN_TRAIT_TYPE
+/// This turns a parsed PATH_TYPE or FOR_TYPE optionally into a DYN_TRAIT_TYPE
 /// with a TYPE_BOUND_LIST
-fn opt_path_type_bounds_as_dyn_trait_type(p: &mut Parser, path_type_marker: CompletedMarker) {
+fn opt_type_bounds_as_dyn_trait_type(p: &mut Parser, type_marker: CompletedMarker) {
+    assert!(matches!(
+        type_marker.kind(),
+        SyntaxKind::PATH_TYPE | SyntaxKind::FOR_TYPE | SyntaxKind::MACRO_CALL
+    ));
     if !p.at(T![+]) {
         return;
     }
 
     // First create a TYPE_BOUND from the completed PATH_TYPE
-    let m = path_type_marker.precede(p).complete(p, TYPE_BOUND);
+    let m = type_marker.precede(p).complete(p, TYPE_BOUND);
 
     // Next setup a marker for the TYPE_BOUND_LIST
     let m = m.precede(p);

crates/syntax/test_data/parser/inline/ok/0154_no_dyn_trait_leading_for.rast

@@ -0,0 +1,43 @@
+[email protected]
+  [email protected]
+    [email protected] "type"
+    [email protected] " "
+    [email protected]
+      [email protected] "A"
+    [email protected] " "
+    [email protected] "="
+    [email protected] " "
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected] "for"
+            [email protected]
+              [email protected] "<"
+              [email protected]
+                [email protected]
+                  [email protected] "\'a"
+              [email protected] ">"
+            [email protected] " "
+            [email protected]
+              [email protected]
+                [email protected]
+                  [email protected]
+                    [email protected] "Test"
+                  [email protected]
+                    [email protected] "<"
+                    [email protected]
+                      [email protected]
+                        [email protected] "\'a"
+                    [email protected] ">"
+        [email protected] " "
+        [email protected] "+"
+        [email protected] " "
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected]
+                [email protected]
+                  [email protected] "Send"
+    [email protected] ";"
+  [email protected] "\n"

crates/syntax/test_data/parser/inline/ok/0154_no_dyn_trait_leading_for.rs

@@ -0,0 +1 @@
+type A = for<'a> Test<'a> + Send;