encoding/xml: restore changes lost in merge

See golang#43168.

src/encoding/xml/xml.go

@@ -835,12 +835,15 @@ func (d *Decoder) rawToken() (Token, error) {
 		d.ungetc(b)
 
 		a := Attr{}
-		// Tag has a list of attributes bound to a namespace or not.
-		a.Name, ok = d.nsname()
-		// if !ok the attribute name has no namespace
+		if a.Name, ok = d.nsname(); !ok {
+			if d.err == nil {
+				d.err = d.syntaxError("expected attribute name in element")
+			}
+			return nil, d.err
+		}
 		d.space()
 		if b, ok = d.mustgetc(); !ok {
-			d.err = d.syntaxError("expected attribute name in element")
+			// d.err = d.syntaxError("expected attribute name in element")
 			return nil, d.err
 		}
 		if b != '=' { // nsname.Local is the attribute name if xmlns is present otherwise err was returned

src/encoding/xml/xml_test.go

@@ -730,7 +730,7 @@ var characterTests = []struct {
 	{"<?xml version=\"1.0\"?>\x0b<doc/>", "illegal character code U+000B"},
 	{"\xef\xbf\xbe<doc/>", "illegal character code U+FFFE"},
 	{"<?xml version=\"1.0\"?><doc>\r\n<hiya/>\x07<toots/></doc>", "illegal character code U+0007"},
-	{"<?xml version=\"1.0\"?><doc \x12='value'>what's up</doc>", "expected = after attribute name"},
+	{"<?xml version=\"1.0\"?><doc \x12='value'>what's up</doc>", "expected attribute name in element"},
 	{"<doc>&abc\x01;</doc>", "invalid character entity &abc (no semicolon)"},
 	{"<doc>&\x01;</doc>", "invalid character entity & (no semicolon)"},
 	{"<doc>&\xef\xbf\xbe;</doc>", "invalid character entity &\uFFFE;"},