From d55f2eddcb8fb86906e7aa50c829a0a6352ba9e7 Mon Sep 17 00:00:00 2001
From: Rebecca Stambler <rstambler@golang.org>
Date: Tue, 4 Aug 2020 15:26:40 -0400
Subject: [PATCH] internal/lsp/source: fix nil pointer in extract function

Ran into this while debugging another issue.

Change-Id: I154493418c7676a24457a4e11431ad4f0311c07a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/246757
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Baum <joshbaum@google.com>
---
 internal/lsp/source/extract.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/internal/lsp/source/extract.go b/internal/lsp/source/extract.go
index 4725572295..6cac9a3886 100644
--- a/internal/lsp/source/extract.go
+++ b/internal/lsp/source/extract.go
@@ -477,8 +477,8 @@ func adjustRangeForWhitespace(rng span.Range, tok *token.File, content []byte) s
 	rng.Start = tok.Pos(offset)
 
 	offset = tok.Offset(rng.End)
-	for offset-1 >= 0 {
-		if !unicode.IsSpace(rune(content[offset-1])) {
+	for o := offset - 1; 0 <= o && o < len(content); {
+		if !unicode.IsSpace(rune(content[o])) {
 			break
 		}
 		// Move backwards one byte to find a non-whitespace character.