update statement completion for fasta scanner

pkg/analyzer/lib/src/dart/ast/utilities.dart

Index: pkg/analyzer/lib/src/dart/ast/utilities.dart
diff --git a/pkg/analyzer/lib/src/dart/ast/utilities.dart b/pkg/analyzer/lib/src/dart/ast/utilities.dart
index dc303a376d86f22bb5af790a49558326be638be6..ccb388e64c02c03fe1b9925bdbfb846dc2eea667 100644
--- a/pkg/analyzer/lib/src/dart/ast/utilities.dart
+++ b/pkg/analyzer/lib/src/dart/ast/utilities.dart
@@ -3977,7 +3977,10 @@ class NodeLocator extends UnifyingAstVisitor<Object> {
     Token endToken = node.endToken;
     // Don't include synthetic tokens.
     while (endToken != beginToken) {
-      if (endToken.type == TokenType.EOF || !endToken.isSynthetic) {
+      // Fasta scanner reports unterminated string literal errors
+      // and generates a synthetic string token with non-zero length.
+      // Because of this, check for length > 0 rather than !isSynthetic.
+      if (endToken.type == TokenType.EOF || endToken.length > 0) {
         break;
       }
       endToken = endToken.previous;