Flow analysis is not available outside of function bodies and initial…

…izers.

This fixes a group of crashes during fuzz testing.

FAILURE: typedef`(=<?[
[NoSuchMethodError: The method 'nullAwareAccess_rightBegin' was called on null.
Receiver: null
Tried calling: nullAwareAccess_rightBegin(Instance of 'ListLiteralImpl', Instance of 'InterfaceTypeImpl'), #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:54:5)
flutter#1      ResolverVisitor.startNullAwareIndexExpression (package:analyzer/src/generated/resolver.dart:776:26)
flutter#2      ResolverVisitor.visitIndexExpression (package:analyzer/src/generated/resolver.dart:1585:5)
flutter#3      IndexExpressionImpl.accept (package:analyzer/src/dart/ast/ast.dart:5993:49)
flutter#4      DefaultFormalParameterImpl.visitChildren (package:analyzer/src/dart/ast/ast.dart:3008:20)
#5      ResolverVisitor.visitNode (package:analyzer/src/generated/resolver.dart:1743:10)
flutter#6      UnifyingAstVisitor.visitDefaultFormalParameter (package:analyzer/dart/ast/visitor.dart:3198:65)
flutter#7      ResolverVisitor.visitDefaultFormalParameter (package:analyzer/src/generated/resolver.dart:1239:11)
flutter#8      DefaultFormalParameterImpl.accept (package:analyzer/src/dart/ast/ast.dart:3003:15)
flutter#9      NodeListImpl.accept (package:analyzer/src/dart/ast/ast.dart:7611:20)
flutter#10     FormalParameterListImpl.visitChildren (package:analyzer/src/dart/ast/ast.dart:4493:17)
flutter#11     ResolverVisitor.visitNode (package:analyzer/src/generated/resolver.dart:1743:10)
flutter#12     UnifyingAstVisitor.visitFormalParameterList (package:analyzer/dart/ast/visitor.dart:3258:59)
flutter#13     ScopedVisitor.visitFormalParameterList (package:analyzer/src/generated/resolver.dart:2717:11)
flutter#14     FormalParameterListImpl.accept (package:analyzer/src/dart/ast/ast.dart:4489:49)
flutter#15     FunctionTypeAliasImpl.visitChildren (package:analyzer/src/dart/ast/ast.dart:5166:18)
flutter#16     ResolverVisitor.visitNode (package:analyzer/src/generated/resolver.dart:1743:10)
flutter#17     UnifyingAstVisitor.visitFunctionTypeAlias (package:analyzer/dart/ast/visitor.dart:3285:55)
flutter#18     ScopedVisitor.visitFunctionTypeAliasInScope (package:analyzer/src/generated/resolver.dart:2819:11)
flutter#19     ResolverVisitor.visitFunctionTypeAliasInScope (package:analyzer/src/generated/resolver.dart:1490:11)
flutter#20     ScopedVisitor.visitFunctionTypeAlias (package:analyzer/src/generated/resolver.dart:2812:7)
#21     ResolverVisitor.visitFunctionTypeAlias (package:analyzer/src/generated/resolver.dart:1482:13)
#22     FunctionTypeAliasImpl.accept (package:analyzer/src/dart/ast/ast.dart:5158:49)
#23     ResolverVisitor.visitCompilationUnit (package:analyzer/src/generated/resolver.dart:1088:23)
#24     CompilationUnitImpl.accept (package:analyzer/src/dart/ast/ast.dart:2134:49)
#25     LibraryAnalyzer._resolveFile (package:analyzer/src/dart/analysis/library_analyzer.dart:706:10)

Continues //dart-review.googlesource.com/c/sdk/+/175187

Change-Id: I9518363961b4adcf7f57c2f0661151ef74efc2f5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/175906
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/lib/src/generated/resolver.dart

@@ -771,26 +771,29 @@ class ResolverVisitor extends ScopedVisitor {
   }
 
   void startNullAwareIndexExpression(IndexExpression node) {
-    if (_migratableAstInfoProvider.isIndexExpressionNullAware(node) &&
-        _flowAnalysis != null) {
-      _flowAnalysis.flow.nullAwareAccess_rightBegin(
-          node.target, node.realTarget.staticType ?? typeProvider.dynamicType);
-      _unfinishedNullShorts.add(node.nullShortingTermination);
+    if (_migratableAstInfoProvider.isIndexExpressionNullAware(node)) {
+      var flow = _flowAnalysis?.flow;
+      if (flow != null) {
+        flow.nullAwareAccess_rightBegin(node.target,
+            node.realTarget.staticType ?? typeProvider.dynamicType);
+        _unfinishedNullShorts.add(node.nullShortingTermination);
+      }
     }
   }
 
-  void startNullAwarePropertyAccess(
-    PropertyAccess node,
-  ) {
-    if (_migratableAstInfoProvider.isPropertyAccessNullAware(node) &&
-        _flowAnalysis != null) {
-      var target = node.target;
-      if (target is SimpleIdentifier && target.staticElement is ClassElement) {
-        // `?.` to access static methods is equivalent to `.`, so do nothing.
-      } else {
-        _flowAnalysis.flow.nullAwareAccess_rightBegin(
-            target, node.realTarget.staticType ?? typeProvider.dynamicType);
-        _unfinishedNullShorts.add(node.nullShortingTermination);
+  void startNullAwarePropertyAccess(PropertyAccess node) {
+    if (_migratableAstInfoProvider.isPropertyAccessNullAware(node)) {
+      var flow = _flowAnalysis?.flow;
+      if (flow != null) {
+        var target = node.target;
+        if (target is SimpleIdentifier &&
+            target.staticElement is ClassElement) {
+          // `?.` to access static methods is equivalent to `.`, so do nothing.
+        } else {
+          flow.nullAwareAccess_rightBegin(
+              target, node.realTarget.staticType ?? typeProvider.dynamicType);
+          _unfinishedNullShorts.add(node.nullShortingTermination);
+        }
       }
     }
   }
@@ -1684,14 +1687,17 @@ class ResolverVisitor extends ScopedVisitor {
     var target = node.target;
     target?.accept(this);
 
-    if (_migratableAstInfoProvider.isMethodInvocationNullAware(node) &&
-        _flowAnalysis != null) {
-      if (target is SimpleIdentifier && target.staticElement is ClassElement) {
-        // `?.` to access static methods is equivalent to `.`, so do nothing.
-      } else {
-        _flowAnalysis.flow.nullAwareAccess_rightBegin(
-            target, node.realTarget.staticType ?? typeProvider.dynamicType);
-        _unfinishedNullShorts.add(node.nullShortingTermination);
+    if (_migratableAstInfoProvider.isMethodInvocationNullAware(node)) {
+      var flow = _flowAnalysis?.flow;
+      if (flow != null) {
+        if (target is SimpleIdentifier &&
+            target.staticElement is ClassElement) {
+          // `?.` to access static methods is equivalent to `.`, so do nothing.
+        } else {
+          flow.nullAwareAccess_rightBegin(
+              target, node.realTarget.staticType ?? typeProvider.dynamicType);
+          _unfinishedNullShorts.add(node.nullShortingTermination);
+        }
       }
     }
 

pkg/analyzer/test/src/dart/resolution/index_expression_test.dart

@@ -29,6 +29,19 @@ void f({a = b?[0]}) {}
     );
   }
 
+  test_invalid_inDefaultValue_nullAware2() async {
+    await assertInvalidTestCode(r'''
+typedef void F({a = b?[0]});
+''');
+
+    assertIndexExpression(
+      findNode.index('[0]'),
+      readElement: null,
+      writeElement: null,
+      type: 'dynamic',
+    );
+  }
+
   test_read() async {
     await assertNoErrorsInCode(r'''
 class A {

pkg/analyzer/test/src/dart/resolution/method_invocation_test.dart

@@ -1718,6 +1718,20 @@ void f({a = b?.foo()}) {}
     );
   }
 
+  test_invalid_inDefaultValue_nullAware2() async {
+    await assertInvalidTestCode('''
+typedef void F({a = b?.foo()});
+''');
+
+    assertMethodInvocation2(
+      findNode.methodInvocation('?.foo()'),
+      element: null,
+      typeArgumentTypes: [],
+      invokeType: 'dynamic',
+      type: 'dynamic',
+    );
+  }
+
   test_namedArgument() async {
     var question = typeToStringWithNullability ? '?' : '';
     await assertNoErrorsInCode('''

pkg/analyzer/test/src/dart/resolution/property_access_test.dart

@@ -250,6 +250,18 @@ void f({a = b?.foo}) {}
     );
   }
 
+  test_invalid_inDefaultValue_nullAware2() async {
+    await assertInvalidTestCode('''
+typedef void F({a = b?.foo});
+''');
+
+    assertPropertyAccess2(
+      findNode.propertyAccess('?.foo'),
+      element: null,
+      type: 'dynamic',
+    );
+  }
+
   test_invalid_inDefaultValue_nullAware_cascade() async {
     await assertInvalidTestCode('''
 void f({a = b?..foo}) {}