Merge #3127

3127: Support unnamed arguments in function pointers r=edwin0cheng a=hanmertens

Fixes #3089

Co-authored-by: Han Mertens <[email protected]>

Author: bors[bot]

crates/ra_parser/src/grammar/params.rs

@@ -114,8 +114,11 @@ fn value_parameter(p: &mut Parser, flavor: Flavor) {
         // test fn_pointer_param_ident_path
         // type Foo = fn(Bar::Baz);
         // type Qux = fn(baz: Bar::Baz);
+
+        // test fn_pointer_unnamed_arg
+        // type Foo = fn(_: bar);
         Flavor::FnPointer => {
-            if p.at(IDENT) && p.nth(1) == T![:] && !p.nth_at(1, T![::]) {
+            if (p.at(IDENT) || p.at(UNDERSCORE)) && p.nth(1) == T![:] && !p.nth_at(1, T![::]) {
                 patterns::pattern_single(p);
                 types::ascription(p);
             } else {

crates/ra_syntax/test_data/parser/inline/ok/0157_fn_pointer_unnamed_arg.rs

@@ -0,0 +1 @@
+type Foo = fn(_: bar);

crates/ra_syntax/test_data/parser/inline/ok/0157_fn_pointer_unnamed_arg.txt

@@ -0,0 +1,26 @@
+SOURCE_FILE@[0; 23)
+  TYPE_ALIAS_DEF@[0; 22)
+    TYPE_KW@[0; 4) "type"
+    WHITESPACE@[4; 5) " "
+    NAME@[5; 8)
+      IDENT@[5; 8) "Foo"
+    WHITESPACE@[8; 9) " "
+    EQ@[9; 10) "="
+    WHITESPACE@[10; 11) " "
+    FN_POINTER_TYPE@[11; 21)
+      FN_KW@[11; 13) "fn"
+      PARAM_LIST@[13; 21)
+        L_PAREN@[13; 14) "("
+        PARAM@[14; 20)
+          PLACEHOLDER_PAT@[14; 15)
+            UNDERSCORE@[14; 15) "_"
+          COLON@[15; 16) ":"
+          WHITESPACE@[16; 17) " "
+          PATH_TYPE@[17; 20)
+            PATH@[17; 20)
+              PATH_SEGMENT@[17; 20)
+                NAME_REF@[17; 20)
+                  IDENT@[17; 20) "bar"
+        R_PAREN@[20; 21) ")"
+    SEMI@[21; 22) ";"
+  WHITESPACE@[22; 23) "\n"