Add optional thin-arrow ret-type for fn-item

Author: A4-Tacks

crates/parser/src/grammar.rs

@@ -303,6 +303,18 @@ fn opt_ret_type(p: &mut Parser<'_>) -> bool {
     }
 }
 
+fn opt_no_arrow_ret_type(p: &mut Parser<'_>) -> bool {
+    if p.at_ts(PATH_NAME_REF_KINDS) {
+        let m = p.start();
+        p.error("missing thin-arrow `->`");
+        types::type_no_bounds(p);
+        m.complete(p, RET_TYPE);
+        true
+    } else {
+        false
+    }
+}
+
 fn name_r(p: &mut Parser<'_>, recovery: TokenSet) {
     if p.at(IDENT) {
         let m = p.start();

crates/parser/src/grammar/items.rs

@@ -422,7 +422,12 @@ fn fn_(p: &mut Parser<'_>, m: Marker) {
     // test function_ret_type
     // fn foo() {}
     // fn bar() -> () {}
-    opt_ret_type(p);
+    if !opt_ret_type(p) {
+        // test_err function_ret_type_missing_arrow
+        // fn foo() usize {}
+        // fn bar() super::Foo {}
+        opt_no_arrow_ret_type(p);
+    }
 
     // test_err fn_ret_recovery
     // fn foo() -> A>]) { let x = 1; }

crates/parser/test_data/generated/runner.rs

@@ -783,6 +783,10 @@ mod err {
         run_and_expect_errors("test_data/parser/inline/err/fn_ret_recovery.rs");
     }
     #[test]
+    fn function_ret_type_missing_arrow() {
+        run_and_expect_errors("test_data/parser/inline/err/function_ret_type_missing_arrow.rs");
+    }
+    #[test]
     fn gen_fn() {
         run_and_expect_errors_with_edition(
             "test_data/parser/inline/err/gen_fn.rs",

crates/parser/test_data/parser/inline/err/function_ret_type_missing_arrow.rast

@@ -0,0 +1,50 @@
+SOURCE_FILE
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "foo"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    RET_TYPE
+      PATH_TYPE
+        PATH
+          PATH_SEGMENT
+            NAME_REF
+              IDENT "usize"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        R_CURLY "}"
+  WHITESPACE "\n"
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "bar"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    RET_TYPE
+      PATH_TYPE
+        PATH
+          PATH
+            PATH_SEGMENT
+              NAME_REF
+                SUPER_KW "super"
+          COLON2 "::"
+          PATH_SEGMENT
+            NAME_REF
+              IDENT "Foo"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        R_CURLY "}"
+  WHITESPACE "\n"
+error 9: missing thin-arrow `->`
+error 27: missing thin-arrow `->`

crates/parser/test_data/parser/inline/err/function_ret_type_missing_arrow.rs

@@ -0,0 +1,2 @@
+fn foo() usize {}
+fn bar() super::Foo {}