From 7ec0ec3645a481155728020c07685992444a9e4f Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Mon, 15 Aug 2022 15:37:22 -0700
Subject: [PATCH] go/types, types2: skip comparison for operands with invalid
 types

Fixes #54405.

Change-Id: Ia7b2709b83966fa080e41e3d4818527d1e8b49f9
Reviewed-on: https://go-review.googlesource.com/c/go/+/424054
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
---
 src/cmd/compile/internal/types2/expr.go          |  6 ++++++
 .../types2/testdata/fixedbugs/issue54405.go      | 16 ++++++++++++++++
 src/go/types/expr.go                             |  6 ++++++
 src/go/types/testdata/fixedbugs/issue54405.go    | 16 ++++++++++++++++
 4 files changed, 44 insertions(+)
 create mode 100644 src/cmd/compile/internal/types2/testdata/fixedbugs/issue54405.go
 create mode 100644 src/go/types/testdata/fixedbugs/issue54405.go

diff --git a/src/cmd/compile/internal/types2/expr.go b/src/cmd/compile/internal/types2/expr.go
index b11cd1e9d8..ee0792e61c 100644
--- a/src/cmd/compile/internal/types2/expr.go
+++ b/src/cmd/compile/internal/types2/expr.go
@@ -783,6 +783,12 @@ func (check *Checker) implicitTypeAndValue(x *operand, target Type) (Type, const
 
 // If switchCase is true, the operator op is ignored.
 func (check *Checker) comparison(x, y *operand, op syntax.Operator, switchCase bool) {
+	// Avoid spurious errors if any of the operands has an invalid type (issue #54405).
+	if x.typ == Typ[Invalid] || y.typ == Typ[Invalid] {
+		x.mode = invalid
+		return
+	}
+
 	if switchCase {
 		op = syntax.Eql
 	}
diff --git a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue54405.go b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue54405.go
new file mode 100644
index 0000000000..e89d5e1b80
--- /dev/null
+++ b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue54405.go
@@ -0,0 +1,16 @@
+// Copyright 2022 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.
+
+// Test that we don't see spurious errors for ==
+// for values with invalid types due to prior errors.
+
+package p
+
+var x struct {
+	f *NotAType /* ERROR undeclared name */
+}
+var _ = x.f == nil // no error expected here
+
+var y *NotAType  /* ERROR undeclared name */
+var _ = y == nil // no error expected here
diff --git a/src/go/types/expr.go b/src/go/types/expr.go
index 0e8dca3247..4b60123499 100644
--- a/src/go/types/expr.go
+++ b/src/go/types/expr.go
@@ -736,6 +736,12 @@ func (check *Checker) implicitTypeAndValue(x *operand, target Type) (Type, const
 
 // If switchCase is true, the operator op is ignored.
 func (check *Checker) comparison(x, y *operand, op token.Token, switchCase bool) {
+	// Avoid spurious errors if any of the operands has an invalid type (issue #54405).
+	if x.typ == Typ[Invalid] || y.typ == Typ[Invalid] {
+		x.mode = invalid
+		return
+	}
+
 	if switchCase {
 		op = token.EQL
 	}
diff --git a/src/go/types/testdata/fixedbugs/issue54405.go b/src/go/types/testdata/fixedbugs/issue54405.go
new file mode 100644
index 0000000000..e89d5e1b80
--- /dev/null
+++ b/src/go/types/testdata/fixedbugs/issue54405.go
@@ -0,0 +1,16 @@
+// Copyright 2022 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.
+
+// Test that we don't see spurious errors for ==
+// for values with invalid types due to prior errors.
+
+package p
+
+var x struct {
+	f *NotAType /* ERROR undeclared name */
+}
+var _ = x.f == nil // no error expected here
+
+var y *NotAType  /* ERROR undeclared name */
+var _ = y == nil // no error expected here