go/printer: do not panic on *ast.ParenExpr in combinesWithName

Fixes #69206

Change-Id: I1b5a664c22d5739e2c6748d562591f57345b536e
GitHub-Last-Rev: 1798e2c65b
GitHub-Pull-Request: golang/go#69208
Reviewed-on: https://go-review.googlesource.com/c/go/+/610115
Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

src/go/printer/nodes.go

@@ -411,9 +411,7 @@ func combinesWithName(x ast.Expr) bool {
 	case *ast.BinaryExpr:
 		return combinesWithName(x.X) && !isTypeElem(x.Y)
 	case *ast.ParenExpr:
-		// name(x) combines but we are making sure at
-		// the call site that x is never parenthesized.
-		panic("unexpected parenthesized expression")
+		return combinesWithName(x.X)
 	}
 	return false
 }

src/go/printer/testdata/generics.golden

@@ -45,6 +45,8 @@ type _[P T | T] struct{}
 type _[P T | T | T | T] struct{}
 type _[P *T, _ any] struct{}
 type _[P *T,] struct{}
+type _[P *T,] struct{}
+type _[P ~int] struct{}
 type _[P *T, _ any] struct{}
 type _[P T] struct{}
 type _[P T, _ any] struct{}

src/go/printer/testdata/generics.input

@@ -42,6 +42,8 @@ type _[P T | T] struct{}
 type _[P T | T | T | T] struct{}
 type _[P *T, _ any] struct{}
 type _[P (*T),] struct{}
+type _[P ((*T)),] struct{}
+type _[P ((~int)),] struct{}
 type _[P (*T), _ any] struct{}
 type _[P (T),] struct{}
 type _[P (T), _ any] struct{}