cmd/compile: use bufio.Reader directly in lexer

Removes an intermediate layer of functions that was clogging up a
corner of the compiler's profile graph.

I can't measure a performance improvement running a large build
like jujud, but the profile reports less total time spent in
gc.(*lexer).getr.

Change-Id: I3000585cfcb0f9729d3a3859e9023690a6528591
Reviewed-on: https://go-review.googlesource.com/20565
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/test/syntax/ddd.go b/test/syntax/ddd.go
new file mode 100644
index 0000000000..476ae22793
--- /dev/null
+++ b/test/syntax/ddd.go
@@ -0,0 +1,11 @@
+// errorcheck
+
+// Copyright 2016 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.
+
+package main
+
+func f() {
+	g(f..3) // ERROR "unexpected literal \.3, expecting name or \("
+}