cmd/compile: omit file:pos for non-existent, permission errors

Omits printing the file:line:column when trying to open either
* non-existent files
* files without permission

Given:
    go tool compile x.go

For either of x.go not existing, or if no read permissions:

* Before:
    x.go:0: open x.go: no such file or directory
    x.go:0: open x.go: permission denied

* After:
    open x.go: no such file or directory
    open x.go: permission denied

While here, noticed an oddity with the Linux builders, that appear
to always be running under root, hence the test for permission errors
with 0222 -W-*-W-*-W- can't pass on linux-amd64 builders.
The filed bug is #38608.

Fixes #36437

Change-Id: I9645ef73177c286c99547e3a0f3719fa07b35cb5
Reviewed-on: https://go-review.googlesource.com/c/go/+/229357
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/src/cmd/compile/internal/gc/subr.go b/src/cmd/compile/internal/gc/subr.go
index 2bbc5e4ae1..6df9ffc66e 100644
--- a/src/cmd/compile/internal/gc/subr.go
+++ b/src/cmd/compile/internal/gc/subr.go
@@ -60,9 +60,15 @@ func adderrorname(n *Node) {
 }
 
 func adderr(pos src.XPos, format string, args ...interface{}) {
+	msg := fmt.Sprintf(format, args...)
+	// Only add the position if we have a file.
+	// See issue golang.org/issue/11361.
+	if !strings.HasSuffix(msg, ": no such file or directory") && !strings.HasSuffix(msg, ": permission denied") {
+		msg = fmt.Sprintf("%v: %s", linestr(pos), msg)
+	}
 	errors = append(errors, Error{
 		pos: pos,
-		msg: fmt.Sprintf("%v: %s\n", linestr(pos), fmt.Sprintf(format, args...)),
+		msg: msg + "\n",
 	})
 }