Add support for assert statements with messages to the analyzer.

pkg/analyzer/test/generated/parser_test.dart

Index: pkg/analyzer/test/generated/parser_test.dart
diff --git a/pkg/analyzer/test/generated/parser_test.dart b/pkg/analyzer/test/generated/parser_test.dart
index 98e80de36f5522bf50147d2a8d31bbfa39935ccf..dab21e966fe575207aa8f676ca38bf114e48ed7c 100644
--- a/pkg/analyzer/test/generated/parser_test.dart
+++ b/pkg/analyzer/test/generated/parser_test.dart
@@ -3221,6 +3221,17 @@ class B = Object with A {}''',
     expect(expression.thenExpression.isSynthetic, isTrue);
   }
 
+  void test_declarationBeforeDirective() {
+    CompilationUnit unit = ParserTestCase.parseCompilationUnit(
+        "class foo { } import 'bar.dart';",
+        [ParserErrorCode.DIRECTIVE_AFTER_DECLARATION]);
+    expect(unit.directives, hasLength(1));
+    expect(unit.declarations, hasLength(1));
+    ClassDeclaration classDecl = unit.childEntities.first;
+    expect(classDecl, isNotNull);
+    expect(classDecl.name.name, 'foo');
+  }
+
   void test_equalityExpression_missing_LHS() {
     BinaryExpression expression =
         parseExpression("== y", [ParserErrorCode.MISSING_IDENTIFIER]);
@@ -3338,17 +3349,6 @@ class B = Object with A {}''',
     parseExpression("m(f() => 0);", [ParserErrorCode.EXPECTED_TOKEN]);
   }
 
-  void test_declarationBeforeDirective() {
-    CompilationUnit unit = ParserTestCase.parseCompilationUnit(
-        "class foo { } import 'bar.dart';",
-        [ParserErrorCode.DIRECTIVE_AFTER_DECLARATION]);
-    expect(unit.directives, hasLength(1));
-    expect(unit.declarations, hasLength(1));
-    ClassDeclaration classDecl = unit.childEntities.first;
-    expect(classDecl, isNotNull);
-    expect(classDecl.name.name, 'foo');
-  }
-
   void test_importDirectivePartial_as() {
     CompilationUnit unit = ParserTestCase.parseCompilationUnit(
         "import 'b.dart' d as b;", [ParserErrorCode.UNEXPECTED_TOKEN]);
@@ -5045,6 +5045,36 @@ class SimpleParserTest extends ParserTestCase {
     expect(statement.assertKeyword, isNotNull);
     expect(statement.leftParenthesis, isNotNull);
     expect(statement.condition, isNotNull);
+    expect(statement.comma, isNull);
+    expect(statement.message, isNull);
+    expect(statement.rightParenthesis, isNotNull);
+    expect(statement.semicolon, isNotNull);
+  }
+
+  void test_parseAssertStatement_messageLowPrecedence() {
+    // Using a throw expression as an assert message would be silly in
+    // practice, but it's the lowest precedence expression type, so verifying
+    // that it works should give us high confidence that other expression types
+    // will work as well.
+    AssertStatement statement =
+        parse4('parseAssertStatement', 'assert (x, throw "foo");');
+    expect(statement.assertKeyword, isNotNull);
+    expect(statement.leftParenthesis, isNotNull);
+    expect(statement.condition, isNotNull);
+    expect(statement.comma, isNotNull);
+    expect(statement.message, isNotNull);
+    expect(statement.rightParenthesis, isNotNull);
+    expect(statement.semicolon, isNotNull);
+  }
+
+  void test_parseAssertStatement_messageString() {
+    AssertStatement statement =
+        parse4('parseAssertStatement', 'assert (x, "foo");');
+    expect(statement.assertKeyword, isNotNull);
+    expect(statement.leftParenthesis, isNotNull);
+    expect(statement.condition, isNotNull);
+    expect(statement.comma, isNotNull);
+    expect(statement.message, isNotNull);
     expect(statement.rightParenthesis, isNotNull);
     expect(statement.semicolon, isNotNull);
   }