internal/lsp/source: Use file:///C:/ on Windows file system

URI should be started with file:/// always.

Change-Id: I123e577d421de3e85dfec00596fbdb63c2231938
Reviewed-on: https://go-review.googlesource.com/c/153618
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/lsp/source/uri.go

@@ -12,8 +12,6 @@ import (
 	"strings"
 )
 
-const fileSchemePrefix = "file://"
-
 // URI represents the full uri for a file.
 type URI string
 

internal/lsp/source/uri_unix.go

@@ -0,0 +1,9 @@
+// Copyright 2018 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.
+
+// +build !windows
+
+package source
+
+const fileSchemePrefix = "file://"

internal/lsp/source/uri_windows.go

@@ -0,0 +1,9 @@
+// Copyright 2018 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.
+
+// +build windows
+
+package source
+
+const fileSchemePrefix = "file:///"

internal/lsp/source/uri_windows_test.go

@@ -0,0 +1,26 @@
+// Copyright 2018 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.
+
+// +build windows
+
+package source
+
+import (
+	"testing"
+)
+
+func TestURIWindows(t *testing.T) {
+	s := `C:\Windows\System32`
+	uri := ToURI(s)
+	if uri != `file:///C:/Windows/System32` {
+		t.Fatalf("ToURI: got %v want %v", uri, s)
+	}
+	f, err := URI(uri).Filename()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if f != s {
+		t.Fatalf("Filename: got %v want %v", f, s)
+	}
+}