Deprecate 'DartType.isVoid', use 'is VoidType' instead.

Maybe? With an explicit type check we don't try to make an impression
that anything more happens here, e.g. for type parameters.

Similarly, for #36697 we would need to introduce `InvalidType`, which is not `DynamicType`. And so, `DartType.isDynamic` should not return `true` for `InvalidType`, it is not a property that various types may have, and should be replaced with explicit `is DynamicType`.

We also have `UnknownInferredType`, but it should never leak to clients.

Change-Id: I302b06355143d97bb52922c805dbad585a522e0a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/288340
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

Author: scheglov

pkg/analysis_server/lib/src/services/completion/dart/completion_manager.dart

@@ -365,7 +365,7 @@ class DartCompletionRequest {
     );
 
     var opType = OpType.forCompletion(target, offset);
-    if (contextType != null && contextType.isVoid) {
+    if (contextType is VoidType) {
       opType.includeVoidReturnSuggestions = true;
     }
 

pkg/analysis_server/lib/src/services/completion/dart/local_library_contributor.dart

@@ -94,7 +94,7 @@ class LibraryElementSuggestionBuilder extends GeneralizingElementVisitor<void> {
       return;
     }
     var returnType = element.returnType;
-    if (returnType.isVoid) {
+    if (returnType is VoidType) {
       if (opType.includeVoidReturnSuggestions) {
         builder.suggestTopLevelFunction(element, kind: kind, prefix: prefix);
       }

pkg/analysis_server/lib/src/services/completion/dart/local_reference_contributor.dart

@@ -129,7 +129,7 @@ class LocalReferenceContributor extends DartCompletionContributor {
     for (var method in type.methods) {
       if (!method.isStatic) {
         if (_visibilityTracker._isVisible(method.declaration)) {
-          if (!method.returnType.isVoid) {
+          if (method.returnType is! VoidType) {
             if (opType.includeReturnValueSuggestions) {
               memberBuilder.addSuggestionForMethod(
                   method: method,

pkg/analysis_server/lib/src/services/completion/dart/utilities.dart

@@ -102,7 +102,7 @@ CompletionDefaultArgumentList computeCompletionDefaultArgumentList(
       // todo (pq): consider refactoring to share common logic w/
       //  ArgListContributor.buildClosureSuggestions
       final returnType = parameterType.returnType;
-      if (returnType.isVoid) {
+      if (returnType is VoidType) {
         blockBuffer.write('{');
         rangeStart = sb.length + blockBuffer.length;
         blockBuffer.write(' }');

pkg/analysis_server/lib/src/services/correction/dart/add_async.dart

@@ -77,7 +77,7 @@ class AddAsync extends CorrectionProducer {
   /// Return `true` if the [type] is `Future<void>`.
   bool _isFutureVoid(DartType type) {
     if (type is InterfaceType && type.isDartAsyncFuture) {
-      return type.typeArguments[0].isVoid;
+      return type.typeArguments[0] is VoidType;
     }
     return false;
   }

pkg/analysis_server/lib/src/services/correction/dart/assign_to_local_variable.dart

@@ -8,6 +8,7 @@ import 'package:analysis_server/src/services/correction/dart/abstract_producer.d
 import 'package:analysis_server/src/services/correction/name_suggestion.dart';
 import 'package:analysis_server/src/utilities/extensions/ast.dart';
 import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/extensions.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:analyzer_plugin/utilities/assist/assist.dart';
@@ -50,7 +51,7 @@ class AssignToLocalVariable extends CorrectionProducer {
     var offset = expression.offset;
     // prepare expression type
     var type = expression.typeOrThrow;
-    if (type.isVoid) {
+    if (type is VoidType) {
       return;
     }
     // prepare excluded names

pkg/analysis_server/lib/src/services/correction/dart/convert_into_block_body.dart

@@ -6,6 +6,7 @@ import 'package:analysis_server/src/services/correction/assist.dart';
 import 'package:analysis_server/src/services/correction/dart/abstract_producer.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/extensions.dart';
 import 'package:analyzer_plugin/utilities/assist/assist.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
@@ -64,7 +65,7 @@ class ConvertIntoBlockBody extends CorrectionProducer {
     var lines = ['// TODO: implement ${functionElement.displayName}'];
 
     var returnValueType = functionElement.returnType;
-    if (!returnValueType.isVoid) {
+    if (returnValueType is! VoidType) {
       lines.add('throw UnimplementedError();');
     }
     return lines;
@@ -85,9 +86,9 @@ class ConvertIntoBlockBody extends CorrectionProducer {
     var returnValueType = returnValue.typeOrThrow;
     var returnValueCode = utils.getNodeText(returnValue);
     var returnCode = '';
-    if (!returnValueType.isVoid &&
+    if (returnValueType is! VoidType &&
         !returnValueType.isBottom &&
-        !functionElement.returnType.isVoid) {
+        functionElement.returnType is! VoidType) {
       returnCode = 'return ';
     }
     returnCode += '$returnValueCode;';

pkg/analysis_server/lib/src/services/refactoring/legacy/convert_method_to_getter.dart

@@ -11,6 +11,7 @@ import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/dart/analysis/session.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/analysis/session_helper.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:analyzer_plugin/utilities/range_factory.dart';
@@ -88,7 +89,7 @@ class ConvertMethodToGetterRefactoringImpl extends RefactoringImpl
           'Only class methods or top-level functions can be converted to getters.');
     }
     // returns a value
-    if (element.returnType.isVoid) {
+    if (element.returnType is VoidType) {
       return RefactoringStatus.fatal(
           'Cannot convert ${element.kind.displayName} returning void.');
     }

pkg/analysis_server/lib/src/services/refactoring/legacy/extract_local.dart

@@ -20,6 +20,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/utilities.dart';
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ -314,7 +315,7 @@ class ExtractLocalRefactoringImpl extends RefactoringImpl
       if (node is MethodInvocation) {
         var invocation = node;
         var element = invocation.methodName.staticElement;
-        if (element is ExecutableElement && element.returnType.isVoid) {
+        if (element is ExecutableElement && element.returnType is VoidType) {
           if (singleExpression == null) {
             return RefactoringStatus.fatal(
                 'Cannot extract the void expression.',

pkg/analysis_server/tool/code_completion/implicit_type_declarations.dart

@@ -104,7 +104,7 @@ class ImpliedTypeCollector extends RecursiveAstVisitor<void> {
   void handleVariableDeclaration(VariableDeclaration node, DartType? dartType) {
     // If some untyped variable declaration
     if (node.equals != null && dartType == null ||
-        (dartType != null && (dartType.isDynamic || dartType.isVoid))) {
+        (dartType != null && (dartType.isDynamic || dartType is VoidType))) {
       // And if we can determine the type on the RHS of the variable declaration
       var rhsType = node.initializer?.staticType;
       if (rhsType != null && !rhsType.isDynamic) {

pkg/analyzer/CHANGELOG.md

@@ -1,3 +1,6 @@
+## 5.8.0-dev
+* Deprecated `DartType.isVoid`, use `is VoidType` instead.
+
 ## 5.7.1
 * Require SDK `>=2.19.0 <3.0.0` to use `PathNotFoundException` from `dart:io`.
 

pkg/analyzer/lib/dart/element/type.dart

@@ -122,6 +122,7 @@ abstract class DartType {
   bool get isDynamic;
 
   /// Return `true` if this type represents the type 'void'.
+  @Deprecated('Use `is VoidType` instead')
   bool get isVoid;
 
   /// Return the name of this type, or `null` if the type does not have a name,

pkg/analyzer/lib/src/dart/element/type.dart

@@ -1462,6 +1462,7 @@ class VoidTypeImpl extends TypeImpl implements VoidType {
   @override
   int get hashCode => 2;
 
+  @Deprecated('Use `is VoidType` instead')
   @override
   bool get isVoid => true;
 

pkg/analyzer/lib/src/dart/element/type_system.dart

@@ -1100,7 +1100,7 @@ class TypeSystemImpl implements TypeSystem {
 
   @override
   bool isNonNullable(DartType type) {
-    if (type.isDynamic || type.isVoid || type.isDartCoreNull) {
+    if (type.isDynamic || type is VoidType || type.isDartCoreNull) {
       return false;
     } else if (type is TypeParameterTypeImpl && type.promotedBound != null) {
       return isNonNullable(type.promotedBound!);
@@ -1141,7 +1141,7 @@ class TypeSystemImpl implements TypeSystem {
 
   @override
   bool isNullable(DartType type) {
-    if (type.isDynamic || type.isVoid || type.isDartCoreNull) {
+    if (type.isDynamic || type is VoidType || type.isDartCoreNull) {
       return true;
     } else if (type is TypeParameterTypeImpl && type.promotedBound != null) {
       return isNullable(type.promotedBound!);
@@ -1183,7 +1183,7 @@ class TypeSystemImpl implements TypeSystem {
 
   @override
   bool isStrictlyNonNullable(DartType type) {
-    if (type.isDynamic || type.isVoid || type.isDartCoreNull) {
+    if (type.isDynamic || type is VoidType || type.isDartCoreNull) {
       return false;
     } else if (type.nullabilitySuffix != NullabilitySuffix.none) {
       return false;

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

@@ -119,7 +119,7 @@ class AssignmentExpressionResolver {
     DartType rightType, {
     required Map<DartType, NonPromotionReason> Function()? whyNotPromoted,
   }) {
-    if (!writeType.isVoid && _checkForUseOfVoidResult(right)) {
+    if (writeType is! VoidType && _checkForUseOfVoidResult(right)) {
       return;
     }
 
@@ -207,7 +207,7 @@ class AssignmentExpressionResolver {
     // Values of the type void cannot be used.
     // Example: `y += 0`, is not allowed.
     if (operatorType != TokenType.EQ) {
-      if (leftType.isVoid) {
+      if (leftType is VoidType) {
         _errorReporter.reportErrorForToken(
           CompileTimeErrorCode.USE_OF_VOID_RESULT,
           operator,

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

@@ -127,11 +127,11 @@ class BodyInferenceContext {
     // If `R` is `void`, or the function literal is marked `async` and `R` is
     // `FutureOr<void>`, let `S` be `void`.
     if (_typeSystem.isNonNullableByDefault) {
-      if (R.isVoid ||
+      if (R is VoidType ||
           isAsynchronous &&
               R is InterfaceType &&
               R.isDartAsyncFutureOr &&
-              R.typeArguments[0].isVoid) {
+              R.typeArguments[0] is VoidType) {
         return VoidTypeImpl.instance;
       }
     }

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

@@ -222,7 +222,7 @@ class ExtensionMemberResolver {
       substitution,
     );
 
-    if (receiverType.isVoid) {
+    if (receiverType is VoidType) {
       _errorReporter.reportErrorForNode(
           CompileTimeErrorCode.USE_OF_VOID_RESULT, receiverExpression);
     } else if (!_typeSystem.isAssignableTo(receiverType, extendedType)) {

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

@@ -127,7 +127,7 @@ class LegacyTypeAsserter extends GeneralizingAstVisitor<void> {
       return;
     }
 
-    if (type.isDynamic || type.isVoid) {
+    if (type.isDynamic || type is VoidType) {
       return;
     }
 

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

@@ -77,7 +77,7 @@ class PropertyElementResolver with ScopeHelpers {
     var targetType = target.typeOrThrow;
     targetType = _typeSystem.resolveToBound(targetType);
 
-    if (targetType.isVoid) {
+    if (targetType is VoidType) {
       // TODO(scheglov) Report directly in TypePropertyResolver?
       _reportUnresolvedIndex(
         node,
@@ -431,7 +431,7 @@ class PropertyElementResolver with ScopeHelpers {
       );
     }
 
-    if (targetType.isVoid) {
+    if (targetType is VoidType) {
       errorReporter.reportErrorForNode(
         CompileTimeErrorCode.USE_OF_VOID_RESULT,
         propertyName,

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

@@ -1579,12 +1579,13 @@ class BestPracticesVerifier extends RecursiveAstVisitor<void> {
       if (returnType == null) return;
 
       bool isReturnVoid;
-      if (returnType.isVoid) {
+      if (returnType is VoidType) {
         isReturnVoid = true;
       } else if (returnType is ParameterizedType &&
           (returnType.isDartAsyncFuture || returnType.isDartAsyncFutureOr)) {
         var typeArguments = returnType.typeArguments;
-        isReturnVoid = typeArguments.length == 1 && typeArguments.first.isVoid;
+        isReturnVoid =
+            typeArguments.length == 1 && typeArguments.first is VoidType;
       } else {
         isReturnVoid = false;
       }

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

@@ -68,7 +68,7 @@ class LiteralElementVerifier {
   void _verifyElement(CollectionElement? element) {
     if (element is Expression) {
       if (forList || forSet) {
-        if (!elementType!.isVoid &&
+        if (elementType is! VoidType &&
             _errorVerifier.checkForUseOfVoidResult(element)) {
           return;
         }
@@ -103,14 +103,14 @@ class LiteralElementVerifier {
   /// Verify that the [entry]'s key and value are assignable to [mapKeyType]
   /// and [mapValueType].
   void _verifyMapLiteralEntry(MapLiteralEntry entry) {
-    var mapKeyType = this.mapKeyType;
-    if (!mapKeyType!.isVoid &&
+    var mapKeyType = this.mapKeyType!;
+    if (mapKeyType is! VoidType &&
         _errorVerifier.checkForUseOfVoidResult(entry.key)) {
       return;
     }
 
-    var mapValueType = this.mapValueType;
-    if (!mapValueType!.isVoid &&
+    var mapValueType = this.mapValueType!;
+    if (mapValueType is! VoidType &&
         _errorVerifier.checkForUseOfVoidResult(entry.value)) {
       return;
     }