go/types, types2: isParameterized must be able to handle tuples

CL 484615 rewrote isParameterized by handling tuple types only where
they occur (function signatures). However, isParameterized is also
called from Checker.callExpr, with a result parameter list which
is a tuple. This CL handles tuples again.

Fixes #59890.

Change-Id: I35159ff65f23322432557e6abcab939933933d40
Reviewed-on: https://go-review.googlesource.com/c/go/+/490695
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>

5 files changed, 35 insertions, 10 deletions

diff --git a/src/cmd/compile/internal/types2/call.go b/src/cmd/compile/internal/types2/call.go
index 7e8fce4350..20cde9f44e 100644
--- a/src/cmd/compile/internal/types2/call.go
+++ b/src/cmd/compile/internal/types2/call.go
@@ -329,8 +329,8 @@ func (check *Checker) callExpr(x *operand, call *syntax.CallExpr) exprKind {
 	x.expr = call
 	check.hasCallOrRecv = true
 
-	// if type inference failed, a parametrized result must be invalidated
-	// (operands cannot have a parametrized type)
+	// if type inference failed, a parameterized result must be invalidated
+	// (operands cannot have a parameterized type)
 	if x.mode == value && sig.TypeParams().Len() > 0 && isParameterized(sig.TypeParams().list(), x.typ) {
 		x.mode = invalid
 	}
diff --git a/src/cmd/compile/internal/types2/infer.go b/src/cmd/compile/internal/types2/infer.go
index 46f461ea09..dbe621cded 100644
--- a/src/cmd/compile/internal/types2/infer.go
+++ b/src/cmd/compile/internal/types2/infer.go
@@ -498,9 +498,13 @@ func (w *tpWalker) isParameterized(typ Type) (res bool) {
 	case *Pointer:
 		return w.isParameterized(t.base)
 
-	// case *Tuple:
-	//      This case should not occur because tuples only appear
-	//      in signatures where they are handled explicitly.
+	case *Tuple:
+		// This case does not occur from within isParameterized
+		// because tuples only appear in signatures where they
+		// are handled explicitly. But isParameterized is also
+		// called by Checker.callExpr with a function result tuple
+		// if instantiation failed (go.dev/issue/59890).
+		return t != nil && w.varList(t.vars)
 
 	case *Signature:
 		// t.tparams may not be nil if we are looking at a signature
diff --git a/src/go/types/call.go b/src/go/types/call.go
index 418de06e76..979de2338f 100644
--- a/src/go/types/call.go
+++ b/src/go/types/call.go
@@ -334,8 +334,8 @@ func (check *Checker) callExpr(x *operand, call *ast.CallExpr) exprKind {
 	x.expr = call
 	check.hasCallOrRecv = true
 
-	// if type inference failed, a parametrized result must be invalidated
-	// (operands cannot have a parametrized type)
+	// if type inference failed, a parameterized result must be invalidated
+	// (operands cannot have a parameterized type)
 	if x.mode == value && sig.TypeParams().Len() > 0 && isParameterized(sig.TypeParams().list(), x.typ) {
 		x.mode = invalid
 	}
diff --git a/src/go/types/infer.go b/src/go/types/infer.go
index f24c729d7a..3aa66105c4 100644
--- a/src/go/types/infer.go
+++ b/src/go/types/infer.go
@@ -500,9 +500,13 @@ func (w *tpWalker) isParameterized(typ Type) (res bool) {
 	case *Pointer:
 		return w.isParameterized(t.base)
 
-	// case *Tuple:
-	//      This case should not occur because tuples only appear
-	//      in signatures where they are handled explicitly.
+	case *Tuple:
+		// This case does not occur from within isParameterized
+		// because tuples only appear in signatures where they
+		// are handled explicitly. But isParameterized is also
+		// called by Checker.callExpr with a function result tuple
+		// if instantiation failed (go.dev/issue/59890).
+		return t != nil && w.varList(t.vars)
 
 	case *Signature:
 		// t.tparams may not be nil if we are looking at a signature
diff --git a/src/internal/types/testdata/fixedbugs/issue59890.go b/src/internal/types/testdata/fixedbugs/issue59890.go
new file mode 100644
index 0000000000..ed7afd939a
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue59890.go
@@ -0,0 +1,17 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _() { g /* ERROR "cannot infer T" */ () }
+
+func g[T any]() (_ /* ERROR "cannot use _ as value or type" */, int) { panic(0) }
+
+// test case from issue
+
+var _ = append(f /* ERROR "cannot infer T" */ ()())
+
+func f[T any]() (_ /* ERROR "cannot use _" */, _ /* ERROR "cannot use _" */, int) {
+	panic("not implemented")
+}