cmd/vet: polish output of shadow test

This commit modifies the style of a error message in case of -shadow.

Previously such a message would look like:
foo.go:42: declaration of err shadows declaration at shadow.go:13:

Changes of the commit include highlighting the variable name and
removing the ": "(space intended) at the end of the line:
foo.go:42: declaration of "err" shadows declaration at shadow.go:13

Fixes #14585.

Change-Id: Ia6a6bf396668dcba9a24f025a08d8826db31f434
Reviewed-on: https://go-review.googlesource.com/20093
Reviewed-by: Rob Pike <r@golang.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/cmd/vet/main.go b/src/cmd/vet/main.go
index fc3873997b..c401fed0b4 100644
--- a/src/cmd/vet/main.go
+++ b/src/cmd/vet/main.go
@@ -435,17 +435,17 @@ func (f *File) loc(pos token.Pos) string {
 	// expression instead of the inner part with the actual error, the
 	// precision can mislead.
 	posn := f.fset.Position(pos)
-	return fmt.Sprintf("%s:%d: ", posn.Filename, posn.Line)
+	return fmt.Sprintf("%s:%d", posn.Filename, posn.Line)
 }
 
 // Warn reports an error but does not set the exit code.
 func (f *File) Warn(pos token.Pos, args ...interface{}) {
-	fmt.Fprint(os.Stderr, f.loc(pos)+fmt.Sprintln(args...))
+	fmt.Fprintf(os.Stderr, "%s: %s", f.loc(pos), fmt.Sprintln(args...))
 }
 
 // Warnf reports a formatted error but does not set the exit code.
 func (f *File) Warnf(pos token.Pos, format string, args ...interface{}) {
-	fmt.Fprintf(os.Stderr, f.loc(pos)+format+"\n", args...)
+	fmt.Fprintf(os.Stderr, "%s: %s\n", f.loc(pos), fmt.Sprintf(format, args...))
 }
 
 // walkFile walks the file's tree.