Issue 25558. Report an error, but don't crash when AST it too deep.

pkg/analyzer/lib/src/dart/error/syntactic_errors.dart

Index: pkg/analyzer/lib/src/dart/error/syntactic_errors.dart
diff --git a/pkg/analyzer/lib/src/dart/error/syntactic_errors.dart b/pkg/analyzer/lib/src/dart/error/syntactic_errors.dart
index c4b6f316e6d2ac3b6f9a7112290a5e506d8b0f20..35aab58752771151088020853edec4db421d4c8a 100644
--- a/pkg/analyzer/lib/src/dart/error/syntactic_errors.dart
+++ b/pkg/analyzer/lib/src/dart/error/syntactic_errors.dart
@@ -834,6 +834,11 @@ class ParserErrorCode extends ErrorCode {
       "Setters can't be defined within methods or functions.",
       "Try moving the setter outside the method or function.");
 
+  static const ParserErrorCode STACK_OVERFLOW = const ParserErrorCode(
+      'STACK_OVERFLOW',
+      "The file has too many nested expressions or statements.",
+      "Try simplifying the code.");
+
   static const ParserErrorCode STATIC_AFTER_CONST = const ParserErrorCode(
       'STATIC_AFTER_CONST',
       "The modifier 'static' should be before the modifier 'const'.",