cmd/go: fix run errors

$ go run
go run: no go files listed
$ go run ../../pkg/math/bits.go
go run: cannot run non-main package
$

Fixes #3168.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5755064

diff --git a/src/cmd/go/run.go b/src/cmd/go/run.go
index d189d70aac89eb819c70b7e531d7072ba5ae9c71..94cd5929691da5152e877c549feaafada5599eea 100644 (file)
--- a/src/cmd/go/run.go
+++ b/src/cmd/go/run.go
@@ -42,12 +42,15 @@ func runRun(cmd *Command, args []string) {
                i++
        }
        files, cmdArgs := args[:i], args[i:]
+       if len(files) == 0 {
+               fatalf("go run: no go files listed")
+       }
        p := goFilesPackage(files)
        if p.Error != nil {
                fatalf("%s", p.Error)
        }
        if p.Name != "main" {
-               fatalf("cannot run non-main package")
+               fatalf("go run: cannot run non-main package")
        }
        p.target = "" // must build - not up to date
        a1 := b.action(modeBuild, modeBuild, p)