go/parser: expand test cases for bad import

R=gri
CC=golang-dev
https://golang.org/cl/5697047

src/pkg/go/parser/parser_test.go

@@ -207,24 +207,40 @@ func TestVarScope(t *testing.T) {
 }
 
 var imports = map[string]bool{
-	"a":        true,
-	"a/b":      true,
-	"a.b":      true,
-	"m\x61th":  true,
-	"greek/αβ": true,
-	"":         false,
-	"\x00":     false,
-	"\x7f":     false,
-	"a!":       false,
-	"a b":      false,
-	`a\b`:      false,
-	"`a`":      false,
-	"\x80\x80": false,
+	`"a"`:        true,
+	"`a`":        true,
+	`"a/b"`:      true,
+	`"a.b"`:      true,
+	`"m\x61th"`:  true,
+	`"greek/αβ"`: true,
+	`""`:         false,
+
+	// Each of these pairs tests both `` vs "" strings
+	// and also use of invalid characters spelled out as
+	// escape sequences and written directly.
+	// For example `"\x00"` tests import "\x00"
+	// while "`\x00`" tests import `<actual-NUL-byte>`.
+	`"\x00"`:     false,
+	"`\x00`":     false,
+	`"\x7f"`:     false,
+	"`\x7f`":     false,
+	`"a!"`:       false,
+	"`a!`":       false,
+	`"a b"`:      false,
+	"`a b`":      false,
+	`"a\\b"`:     false,
+	"`a\\b`":     false,
+	"\"`a`\"":    false,
+	"`\"a\"`":    false,
+	`"\x80\x80"`: false,
+	"`\x80\x80`": false,
+	`"\xFFFD"`:   false,
+	"`\xFFFD`":   false,
 }
 
 func TestImports(t *testing.T) {
 	for path, isValid := range imports {
-		src := fmt.Sprintf("package p; import %q", path)
+		src := fmt.Sprintf("package p; import %s", path)
 		_, err := ParseFile(fset, "", src, 0)
 		switch {
 		case err != nil && isValid: