cmd/vet: check only for ASCII spaces (0x20) in struct tags

Change-Id: I6e9b5caeca842b6bf72afefb31f5140608b86d20
Reviewed-on: https://go-review.googlesource.com/58530
Run-TryBot: Francesc Campoy Flores <campoy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/vet/structtag.go

@@ -13,7 +13,6 @@ import (
 	"reflect"
 	"strconv"
 	"strings"
-	"unicode"
 )
 
 func init() {
@@ -195,7 +194,7 @@ func validateStructTag(tag string) error {
 			value = value[comma+1:]
 		}
 
-		if strings.IndexFunc(value, unicode.IsSpace) >= 0 {
+		if strings.IndexByte(value, ' ') >= 0 {
 			return errTagValueSpace
 		}
 	}

src/cmd/vet/testdata/structtag.go

@@ -83,15 +83,14 @@ type DuplicateJSONFields struct {
 
 type UnexpectedSpacetest struct {
 	A int `json:"a,omitempty"`
-	B int `json:"b, omitempty"`  // ERROR "suspicious space found in struct tag value"
-	C int `json:"c,omitempty\t"` // ERROR "suspicious space found in struct tag value"
-	D int `json:"d ,omitempty"`
-	E int `json:"e,omitempty, string"` // ERROR "suspicious space found in struct tag value"
-	F int `xml:" f"`                   // ERROR "suspicious space found in struct tag value"
-	G int `xml:"g "`                   // ERROR "suspicious space found in struct tag value"
-	H int `xml:"h ,omitempty"`         // ERROR "suspicious space found in struct tag value"
-	I int `xml:" i"`                   // ERROR "suspicious space found in struct tag value"
-	J int `xml:"j "`                   // ERROR "suspicious space found in struct tag value"
-	K int `xml:"k ,omitempty"`         // ERROR "suspicious space found in struct tag value"
-	L int `foo:" doesn't care "`
+	B int `json:"b, omitempty"` // ERROR "suspicious space found in struct tag value"
+	C int `json:"d ,omitempty"`
+	D int `json:"e,omitempty, string"` // ERROR "suspicious space found in struct tag value"
+	E int `xml:" f"`                   // ERROR "suspicious space found in struct tag value"
+	F int `xml:"g "`                   // ERROR "suspicious space found in struct tag value"
+	G int `xml:"h ,omitempty"`         // ERROR "suspicious space found in struct tag value"
+	H int `xml:" i"`                   // ERROR "suspicious space found in struct tag value"
+	I int `xml:"j "`                   // ERROR "suspicious space found in struct tag value"
+	J int `xml:"k ,omitempty"`         // ERROR "suspicious space found in struct tag value"
+	K int `foo:" doesn't care "`
 }