From: Robert Findley <rfindley@google.com>
Date: Mon, 7 Aug 2023 19:46:34 +0000 (-0400)
Subject: go/types: fix panic in allowVersion when pos is invalid
X-Git-Tag: go1.22rc1~1374
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=008ab9adb8382a274ba25c005a046b912af94809;p=gostls13.git

go/types: fix panic in allowVersion when pos is invalid

CL 515656 updated go/types to use file base as key in the posVers map,
but introduced a panic when the corresponding *token.File is nil.

Check that pos is valid before performing the lookup.

Fixes #61822

Change-Id: I1ac9d48c831a470de8439a50022ba5f59b3e0bed
Reviewed-on: https://go-review.googlesource.com/c/go/+/516738
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Robert Findley <rfindley@google.com>
---

diff --git a/src/go/types/version.go b/src/go/types/version.go
index 2f21e98ad8..0f4d064b74 100644
--- a/src/go/types/version.go
+++ b/src/go/types/version.go
@@ -131,9 +131,10 @@ func (check *Checker) allowVersion(pkg *Package, at positioner, v version) bool
 		return true
 	}
 
-	// If the source file declares its Go version, use that to decide.
-	if check.posVers != nil {
-		fileStart := check.fset.File(at.Pos()).Pos(0)
+	// If the source file declares its Go version and at references a valid
+	// position, use that to decide.
+	if pos := at.Pos(); pos.IsValid() && check.posVers != nil {
+		fileStart := check.fset.File(pos).Pos(0)
 		if src, ok := check.posVers[fileStart]; ok && src.major >= 1 {
 			return !src.before(v)
 		}
diff --git a/src/internal/types/testdata/fixedbugs/issue61822.go b/src/internal/types/testdata/fixedbugs/issue61822.go
new file mode 100644
index 0000000000..0a91ebb7b2
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue61822.go
@@ -0,0 +1,19 @@
+// -lang=go1.19
+
+// 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.
+
+//go:build go1.20
+
+package p
+
+type I[P any] interface {
+	~string | ~int
+	Error() P
+}
+
+func _[P I[string]]() {
+	var x P
+	var _ error = x
+}