Auto merge of #13160 - ChayimFriedman2:parse-parenthesized-type-path-with-coloncolon, r=jonas-schievink

fix: Parse TypePathFn with preceding `::`

e.g. `impl Fn::() -> ()`.

Fixes #13157. This was the problem, not that the path was not at the end.

I could unify the parsing of `::` of TypePathFn with that of generic arg list, but some code relies on the `::` of generic arg list to be inside it.

crates/parser/src/grammar/paths.rs

@@ -118,6 +118,11 @@ fn opt_path_type_args(p: &mut Parser<'_>, mode: Mode) {
     match mode {
         Mode::Use => {}
         Mode::Type => {
+            // test typepathfn_with_coloncolon
+            // type F = Start::(Middle) -> (Middle)::End;
+            if p.at(T![::]) && p.nth_at(2, T!['(']) {
+                p.bump(T![::]);
+            }
             // test path_fn_trait_args
             // type F = Box<Fn(i32) -> ()>;
             if p.at(T!['(']) {

crates/parser/test_data/parser/inline/ok/0202_typepathfn_with_coloncolon.rast

@@ -0,0 +1,43 @@
+SOURCE_FILE
+  TYPE_ALIAS
+    TYPE_KW "type"
+    WHITESPACE " "
+    NAME
+      IDENT "F"
+    WHITESPACE " "
+    EQ "="
+    WHITESPACE " "
+    PATH_TYPE
+      PATH
+        PATH
+          PATH_SEGMENT
+            NAME_REF
+              IDENT "Start"
+            COLON2 "::"
+            PARAM_LIST
+              L_PAREN "("
+              PARAM
+                PATH_TYPE
+                  PATH
+                    PATH_SEGMENT
+                      NAME_REF
+                        IDENT "Middle"
+              R_PAREN ")"
+            WHITESPACE " "
+            RET_TYPE
+              THIN_ARROW "->"
+              WHITESPACE " "
+              PAREN_TYPE
+                L_PAREN "("
+                PATH_TYPE
+                  PATH
+                    PATH_SEGMENT
+                      NAME_REF
+                        IDENT "Middle"
+                R_PAREN ")"
+        COLON2 "::"
+        PATH_SEGMENT
+          NAME_REF
+            IDENT "End"
+    SEMICOLON ";"
+  WHITESPACE "\n"

crates/parser/test_data/parser/inline/ok/0202_typepathfn_with_coloncolon.rs

@@ -0,0 +1 @@
+type F = Start::(Middle) -> (Middle)::End;