go/parser: remove import path string syntax checking

The validity of an import path string is checked by the type checker
(and possibly other tools); it doesn't need to be done by the parser.
Remove the respective code and tests.

Also, adjust a corresponding go/types test which resolves a TODO.

For #54511.

Change-Id: Id1fc80df4e3e83be3ef123da3946ccb8f759779f
Reviewed-on: https://go-review.googlesource.com/c/go/+/424855
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

src/go/parser/parser.go

@@ -21,9 +21,6 @@ import (
 	"go/internal/typeparams"
 	"go/scanner"
 	"go/token"
-	"strconv"
-	"strings"
-	"unicode"
 )
 
 // The parser structure holds the parser's internal state.
@@ -2547,17 +2544,6 @@ func (p *parser) parseStmt() (s ast.Stmt) {
 
 type parseSpecFunction func(doc *ast.CommentGroup, pos token.Pos, keyword token.Token, iota int) ast.Spec
 
-func isValidImport(lit string) bool {
-	const illegalChars = `!"#$%&'()*,:;<=>?[\]^{|}` + "`\uFFFD"
-	s, _ := strconv.Unquote(lit) // go/scanner returns a legal string literal
-	for _, r := range s {
-		if !unicode.IsGraphic(r) || unicode.IsSpace(r) || strings.ContainsRune(illegalChars, r) {
-			return false
-		}
-	}
-	return s != ""
-}
-
 func (p *parser) parseImportSpec(doc *ast.CommentGroup, _ token.Pos, _ token.Token, _ int) ast.Spec {
 	if p.trace {
 		defer un(trace(p, "ImportSpec"))
@@ -2576,9 +2562,6 @@ func (p *parser) parseImportSpec(doc *ast.CommentGroup, _ token.Pos, _ token.Tok
 	var path string
 	if p.tok == token.STRING {
 		path = p.lit
-		if !isValidImport(path) {
-			p.error(pos, "invalid import path: "+path)
-		}
 		p.next()
 	} else {
 		p.expect(token.STRING) // use expect() error handling

src/go/parser/parser_test.go

@@ -310,51 +310,6 @@ type s3b struct { a, b *s3b; c []float }
 	}
 }
 
-var imports = map[string]bool{
-	`"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 %s", path)
-		_, err := ParseFile(token.NewFileSet(), "", src, 0)
-		switch {
-		case err != nil && isValid:
-			t.Errorf("ParseFile(%s): got %v; expected no error", src, err)
-		case err == nil && !isValid:
-			t.Errorf("ParseFile(%s): got no error; expected one", src)
-		}
-	}
-}
-
 func TestCommentGroups(t *testing.T) {
 	f, err := ParseFile(token.NewFileSet(), "", `
 package p /* 1a */ /* 1b */      /* 1c */ // 1d

src/go/types/testdata/check/importdecl0/importdecl0b.go

@@ -12,12 +12,9 @@ import . /* ERROR .unsafe. imported but not used */ "unsafe"
 import . "fmt"     // declares Println in file scope
 
 import (
-	// TODO(gri) At the moment, 2 errors are reported because both go/parser
-	// and the type checker report it. Eventually, this test should not be
-	// done by the parser anymore.
-	"" /* ERROR invalid import path */ /* ERROR invalid import path */
-	"a!b" /* ERROR invalid import path */ /* ERROR invalid import path */
-	"abc\xffdef" /* ERROR invalid import path */ /* ERROR invalid import path */
+	"" /* ERROR invalid import path */
+	"a!b" /* ERROR invalid import path */
+	"abc\xffdef" /* ERROR invalid import path */
 )
 
 // using "math" in this file doesn't affect its use in other files