go/types: collect methods with parenthesized receiver types

The existing code simply dropped them on the floor. Don't do that.

Fixes #23130.

Change-Id: I10f20e41f2c466a76519983253f87af7cf6d5e70
Reviewed-on: https://go-review.googlesource.com/83918Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/go/types/resolver.go

@@ -417,9 +417,9 @@ func (check *Checker) collectObjects() {
 					// receiver name. They will be type-checked later, with regular
 					// functions.
 					if list := d.Recv.List; len(list) > 0 {
-						typ := list[0].Type
+						typ := unparen(list[0].Type)
 						if ptr, _ := typ.(*ast.StarExpr); ptr != nil {
-							typ = ptr.X
+							typ = unparen(ptr.X)
 						}
 						if base, _ := typ.(*ast.Ident); base != nil && base.Name != "_" {
 							check.assocMethod(base.Name, obj)

src/go/types/testdata/decls2b.src

@@ -63,3 +63,13 @@ func ((*T7)) m3() {}
 func (x *(T7),) m4() {}
 func (x (*(T7)),) m5() {}
 func (x ((*((T7)))),) m6() {}
+
+// Check that methods with parenthesized receiver are actually present (issue #23130).
+var (
+	_ = T7.m1
+	_ = T7.m2
+	_ = (*T7).m3
+	_ = (*T7).m4
+	_ = (*T7).m5
+	_ = (*T7).m6
+)
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