Report errors for the new top-level inference rules.

We also stop type inference most of these cases with task based analysis.
Summary based analysis is not changed yet.

[email protected]
BUG=

Review-Url: https://codereview.chromium.org/2782533002 .

Author: scheglov

pkg/analyzer/lib/error/error.dart

@@ -638,6 +638,13 @@ const List<ErrorCode> errorCodeValues = const [
   StrongModeCode.NO_DEFAULT_BOUNDS,
   StrongModeCode.NON_GROUND_TYPE_CHECK_INFO,
   StrongModeCode.NOT_INSTANTIATED_BOUND,
+  StrongModeCode.TOP_LEVEL_CYCLE,
+  StrongModeCode.TOP_LEVEL_FUNCTION_LITERAL_BLOCK,
+  StrongModeCode.TOP_LEVEL_FUNCTION_LITERAL_PARAMETER,
+  StrongModeCode.TOP_LEVEL_IDENTIFIER_NO_TYPE,
+  StrongModeCode.TOP_LEVEL_INSTANCE_GETTER,
+  StrongModeCode.TOP_LEVEL_TYPE_ARGUMENTS,
+  StrongModeCode.TOP_LEVEL_UNSUPPORTED,
   StrongModeCode.UNSAFE_BLOCK_CLOSURE_INFERENCE,
   TodoCode.TODO,
 ];

pkg/analyzer/lib/src/dart/analysis/driver.dart

@@ -72,7 +72,7 @@ class AnalysisDriver implements AnalysisDriverGeneric {
   /**
    * The version of data format, should be incremented on every format change.
    */
-  static const int DATA_VERSION = 27;
+  static const int DATA_VERSION = 28;
 
   /**
    * The number of exception contexts allowed to write. Once this field is

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

@@ -4951,6 +4951,50 @@ class StrongModeCode extends ErrorCode {
       "Type parameter bound types must be instantiated.",
       "Try adding type arguments.");
 
+  static const StrongModeCode TOP_LEVEL_CYCLE = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'TOP_LEVEL_CYCLE',
+      "The type of '{0}' can't be inferred because it depends on itself through the cycle: {1}.",
+      "Try adding an explicit type to one or more of the variables in the cycle in order to break the cycle.");
+
+  static const StrongModeCode TOP_LEVEL_FUNCTION_LITERAL_BLOCK =
+      const StrongModeCode(
+          ErrorType.COMPILE_TIME_ERROR,
+          'TOP_LEVEL_FUNCTION_LITERAL_BLOCK',
+          "The type of the function literal can't be inferred because the literal has a block as its body.",
+          "Try adding an explicit type to the variable.");
+
+  static const StrongModeCode TOP_LEVEL_FUNCTION_LITERAL_PARAMETER =
+      const StrongModeCode(
+          ErrorType.COMPILE_TIME_ERROR,
+          'TOP_LEVEL_FUNCTION_LITERAL_PARAMETER',
+          "The type of '{0}' can't be inferred because the parameter '{1}' does not have an explicit type.",
+          "Try adding an explicit type to the parameter '{1}', or add an explicit type for '{0}'.");
+
+  static const StrongModeCode TOP_LEVEL_IDENTIFIER_NO_TYPE = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'TOP_LEVEL_IDENTIFIER_NO_TYPE',
+      "The type of '{0}' can't be inferred because the type of '{1}' couldn't be inferred.",
+      "Try adding an explicit type to either the variable '{0}' or the variable '{1}'.");
+
+  static const StrongModeCode TOP_LEVEL_INSTANCE_GETTER = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'TOP_LEVEL_INSTANCE_GETTER',
+      "The type of '{0}' can't be inferred because of the use of the instance getter '{1}'.",
+      "Try removing the use of the instance getter {1}, or add an explicit type for '{0}'.");
+
+  static const StrongModeCode TOP_LEVEL_TYPE_ARGUMENTS = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'TOP_LEVEL_TYPE_ARGUMENTS',
+      "The type of '{0}' can't be inferred because type arguments were not given for '{1}'.",
+      "Try adding type arguments for '{1}', or add an explicit type for '{0}'.");
+
+  static const StrongModeCode TOP_LEVEL_UNSUPPORTED = const StrongModeCode(
+      ErrorType.COMPILE_TIME_ERROR,
+      'TOP_LEVEL_UNSUPPORTED',
+      "The type of '{0}' can't be inferred because {1} expressions aren't supported.",
+      "Try adding an explicit type for '{0}'.");
+
   static const StrongModeCode UNSAFE_BLOCK_CLOSURE_INFERENCE = const StrongModeCode(
       ErrorType.STATIC_WARNING,
       'UNSAFE_BLOCK_CLOSURE_INFERENCE',

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

@@ -5021,6 +5021,12 @@ class ResolverVisitor extends ScopedVisitor {
    */
   bool resolveOnlyCommentInFunctionBody = false;
 
+  /**
+   * This flag is set to `true` while the type of a top-level variable or a
+   * class field is being inferred using its initializer.
+   */
+  bool isTopLevelInference;
+
   /**
    * Body of the function currently being analyzed, if any.
    */
@@ -5050,7 +5056,7 @@ class ResolverVisitor extends ScopedVisitor {
    */
   ResolverVisitor(LibraryElement definingLibrary, Source source,
       TypeProvider typeProvider, AnalysisErrorListener errorListener,
-      {Scope nameScope})
+      {Scope nameScope, this.isTopLevelInference: false})
       : super(definingLibrary, source, typeProvider, errorListener,
             nameScope: nameScope) {
     AnalysisOptions options = definingLibrary.context.analysisOptions;
@@ -5550,11 +5556,14 @@ class ResolverVisitor extends ScopedVisitor {
 
   @override
   Object visitBlockFunctionBody(BlockFunctionBody node) {
+    bool wasTopLevelInference = isTopLevelInference;
+    isTopLevelInference = false;
     _overrideManager.enterScope();
     try {
       inferenceContext.pushReturnContext(node);
       super.visitBlockFunctionBody(node);
     } finally {
+      isTopLevelInference = wasTopLevelInference;
       _overrideManager.exitScope();
       inferenceContext.popReturnContext(node);
     }
@@ -5873,10 +5882,13 @@ class ResolverVisitor extends ScopedVisitor {
 
   @override
   Object visitFieldDeclaration(FieldDeclaration node) {
+    bool wasTopLevelInference = isTopLevelInference;
+    isTopLevelInference = node.fields.type == null;
     _overrideManager.enterScope();
     try {
       super.visitFieldDeclaration(node);
     } finally {
+      isTopLevelInference = wasTopLevelInference;
       Map<VariableElement, DartType> overrides =
           _overrideManager.captureOverrides(node.fields);
       _overrideManager.exitScope();
@@ -6379,10 +6391,13 @@ class ResolverVisitor extends ScopedVisitor {
 
   @override
   Object visitTopLevelVariableDeclaration(TopLevelVariableDeclaration node) {
+    bool wasTopLevelInference = isTopLevelInference;
+    isTopLevelInference = node.variables.type == null;
     _overrideManager.enterScope();
     try {
       super.visitTopLevelVariableDeclaration(node);
     } finally {
+      isTopLevelInference = wasTopLevelInference;
       Map<VariableElement, DartType> overrides =
           _overrideManager.captureOverrides(node.variables);
       _overrideManager.exitScope();
@@ -6661,6 +6676,11 @@ class ResolverVisitor extends ScopedVisitor {
         uninstantiatedType is FunctionType &&
         uninstantiatedType.typeFormals.isNotEmpty &&
         ts is StrongTypeSystemImpl) {
+      if (isTopLevelInference) {
+        if (uninstantiatedType.typeFormals.isNotEmpty) {
+          return null;
+        }
+      }
       return ts.inferGenericFunctionOrType/*<FunctionType>*/(
           uninstantiatedType,
           ParameterElement.EMPTY_LIST,