fix #26141, add support for type arguments to constants

pkg/analyzer/lib/src/dart/constant/evaluation.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.src.dart.constant.evaluation;
 
 import 'dart:collection';
 
 import 'package:analyzer/context/declared_variables.dart';
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 57 matching lines @@
    * The set of variables declared on the command line using '-D'.
    */
   final DeclaredVariables _declaredVariables;
 
   /**
    * Validator used to verify correct dependency analysis when running unit
    * tests.
    */
   final ConstantEvaluationValidator validator;
 
+  /** Whether we are running in strong mode. */
+  final bool strongMode;
+
   /**
    * Initialize a newly created [ConstantEvaluationEngine].  The [typeProvider]
    * is used to access known types.  [_declaredVariables] is the set of
    * variables declared on the command line using '-D'.  The [validator], if
    * given, is used to verify correct dependency analysis when running unit
    * tests.
    */
-  ConstantEvaluationEngine(this.typeProvider, this._declaredVariables,
+  ConstantEvaluationEngine(TypeProvider typeProvider, this._declaredVariables,
       {ConstantEvaluationValidator validator, TypeSystem typeSystem})
-      : validator =
+      : typeProvider = typeProvider,
+        strongMode =
+            typeProvider.objectType.element.context.analysisOptions.strongMode,
+        validator =
             validator ?? new ConstantEvaluationValidator_ForProduction(),
         typeSystem = typeSystem ?? new TypeSystemImpl();
 
   /**
    * Check that the arguments to a call to fromEnvironment() are correct. The
    * [arguments] are the AST nodes of the arguments. The [argumentValues] are
    * the values of the unnamed arguments. The [namedArgumentValues] are the
    * values of the named arguments. The [expectedDefaultValueType] is the
    * allowed type of the "defaultValue" parameter (if present). Note:
    * "defaultValue" is always allowed to be null. Return `true` if the arguments
@@ skipping 304 matching lines @@
         // The VM would use the built-in default value, but we don't want to do
         // that for analysis because it's likely to lead to cascading errors.
         // So just leave [value] in the unknown state.
       }
     }
     return value;
   }
 
   DartObjectImpl evaluateConstructorCall(
       AstNode node,
-      NodeList<Expression> arguments,
+      List<Expression> arguments,
       ConstructorElement constructor,
       ConstantVisitor constantVisitor,
       ErrorReporter errorReporter) {
     if (!getConstructorImpl(constructor).isCycleFree) {
       // It's not safe to evaluate this constructor, so bail out.
       // TODO(paulberry): ensure that a reasonable error message is produced
       // in this case, as well as other cases involving constant expression
       // circularities (e.g. "compile-time constant expression depends on
       // itself")
       return new DartObjectImpl.validWithUnknownValue(constructor.returnType);
@@ skipping 85 matching lines @@
     List<ConstructorInitializer> initializers =
         constructorBase.constantInitializers;
     if (initializers == null) {
       // This can happen in some cases where there are compile errors in the
       // code being analyzed (for example if the code is trying to create a
       // const instance using a non-const constructor, or the node we're
       // visiting is involved in a cycle).  The error has already been reported,
       // so consider it an unknown value to suppress further errors.
       return new DartObjectImpl.validWithUnknownValue(definingClass);
     }
-    HashMap<String, DartObjectImpl> fieldMap =
-        new HashMap<String, DartObjectImpl>();
+
+    // In strong mode, we allow constants to have type arguments.
+    //
+    // They will be added to the lexical environment when evaluating
+    // subexpressions.
+    HashMap<String, DartObjectImpl> typeArgumentMap;
+    if (strongMode) {
+      // Instantiate the constructor with the in-scope type arguments.
+      definingClass = constantVisitor.evaluateType(definingClass);
+      constructor = ConstructorMember.from(constructorBase, definingClass);
+
+      typeArgumentMap = new HashMap<String, DartObjectImpl>.fromIterables(
+          definingClass.typeParameters.map((t) => t.name),
+          definingClass.typeArguments.map(constantVisitor.typeConstant));
+    }
+
+    var fieldMap = new HashMap<String, DartObjectImpl>();
+    var fieldInitVisitor = new ConstantVisitor(this, errorReporter,
+        lexicalEnvironment: typeArgumentMap);
     // Start with final fields that are initialized at their declaration site.
-    for (FieldElement field in constructor.enclosingElement.fields) {
+    List<FieldElement> fields = constructor.enclosingElement.fields;
+    for (int i = 0; i < fields.length; i++) {
+      FieldElement field = fields[i];
       if ((field.isFinal || field.isConst) &&
           !field.isStatic &&
           field is ConstFieldElementImpl) {
         validator.beforeGetFieldEvaluationResult(field);
-        EvaluationResultImpl evaluationResult = field.evaluationResult;
+
+        DartObjectImpl fieldValue;
+        if (strongMode) {
+          fieldValue = field.constantInitializer.accept(fieldInitVisitor);
+        } else {
+          fieldValue = field.evaluationResult?.value;
+        }
         // It is possible that the evaluation result is null.
         // This happens for example when we have duplicate fields.
         // class Test {final x = 1; final x = 2; const Test();}
-        if (evaluationResult == null) {
+        if (fieldValue == null) {
           continue;
         }
         // Match the value and the type.
         DartType fieldType =
             FieldMember.from(field, constructor.returnType).type;
-        DartObjectImpl fieldValue = evaluationResult.value;
         if (fieldValue != null && !runtimeTypeMatch(fieldValue, fieldType)) {
           errorReporter.reportErrorForNode(
               CheckedModeCompileTimeErrorCode
                   .CONST_CONSTRUCTOR_FIELD_TYPE_MISMATCH,
               node,
               [fieldValue.type, field.name, fieldType]);
         }
         fieldMap[field.name] = fieldValue;
       }
     }
     // Now evaluate the constructor declaration.
     HashMap<String, DartObjectImpl> parameterMap =
         new HashMap<String, DartObjectImpl>();
     List<ParameterElement> parameters = constructor.parameters;
     int parameterCount = parameters.length;
+
     for (int i = 0; i < parameterCount; i++) {
       ParameterElement parameter = parameters[i];
       ParameterElement baseParameter = parameter;
       while (baseParameter is ParameterMember) {
         baseParameter = (baseParameter as ParameterMember).baseElement;
       }
       DartObjectImpl argumentValue = null;
       AstNode errorTarget = null;
       if (baseParameter.parameterKind == ParameterKind.NAMED) {
         argumentValue = namedArgumentValues[baseParameter.name];
         errorTarget = namedArgumentNodes[baseParameter.name];
       } else if (i < argumentCount) {
         argumentValue = argumentValues[i];
         errorTarget = argumentNodes[i];
       }
       if (errorTarget == null) {
         // No argument node that we can direct error messages to, because we
         // are handling an optional parameter that wasn't specified.  So just
         // direct error messages to the constructor call.
         errorTarget = node;
       }
       if (argumentValue == null && baseParameter is ParameterElementImpl) {
         // The parameter is an optional positional parameter for which no value
         // was provided, so use the default value.
         validator.beforeGetParameterDefault(baseParameter);
-        EvaluationResultImpl evaluationResult = baseParameter.evaluationResult;
-        if (evaluationResult == null) {
-          // No default was provided, so the default value is null.
-          argumentValue = typeProvider.nullObject;
-        } else if (evaluationResult.value != null) {
-          argumentValue = evaluationResult.value;
+        if (strongMode && baseParameter is ConstVariableElement) {
+          var defaultValue =
+              (baseParameter as ConstVariableElement).constantInitializer;
+          if (defaultValue == null) {
+            argumentValue = typeProvider.nullObject;
+          } else {
+            argumentValue = defaultValue.accept(fieldInitVisitor);
+          }
+        } else {
+          EvaluationResultImpl evaluationResult =
+              baseParameter.evaluationResult;
+          if (evaluationResult == null) {
+            // No default was provided, so the default value is null.
+            argumentValue = typeProvider.nullObject;
+          } else if (evaluationResult.value != null) {
+            argumentValue = evaluationResult.value;
+          }
         }
       }
       if (argumentValue != null) {
         if (!runtimeTypeMatch(argumentValue, parameter.type)) {
           errorReporter.reportErrorForNode(
               CheckedModeCompileTimeErrorCode
                   .CONST_CONSTRUCTOR_PARAM_TYPE_MISMATCH,
               errorTarget,
               [argumentValue.type, parameter.type]);
         }
@@ skipping 77 matching lines @@
     }
     // Evaluate explicit or implicit call to super().
     InterfaceType superclass = definingClass.superclass;
     if (superclass != null && !superclass.isObject) {
       ConstructorElement superConstructor =
           superclass.lookUpConstructor(superName, constructor.library);
       if (superConstructor != null) {
         if (superArguments == null) {
           superArguments = new NodeList<Expression>(null);
         }
+
         evaluateSuperConstructorCall(node, fieldMap, superConstructor,
             superArguments, initializerVisitor, errorReporter);
       }
     }
     return new DartObjectImpl(definingClass, new GenericState(fieldMap));
   }
 
   void evaluateSuperConstructorCall(
       AstNode node,
       HashMap<String, DartObjectImpl> fieldMap,
       ConstructorElement superConstructor,
-      NodeList<Expression> superArguments,
+      List<Expression> superArguments,
       ConstantVisitor initializerVisitor,
       ErrorReporter errorReporter) {
     if (superConstructor != null && superConstructor.isConst) {
       DartObjectImpl evaluationResult = evaluateConstructorCall(node,
           superArguments, superConstructor, initializerVisitor, errorReporter);
       if (evaluationResult != null) {
         fieldMap[GenericState.SUPERCLASS_FIELD] = evaluationResult;
       }
     }
   }
@@ skipping 522 matching lines @@
       // TODO(brianwilkerson) Figure out which error to report.
       _error(node, null);
       return null;
     }
     ConstructorElement constructor = node.staticElement;
     if (constructor == null) {
       // Couldn't resolve the constructor so we can't compute a value.  No
       // problem - the error has already been reported.
       return null;
     }
+
     return evaluationEngine.evaluateConstructorCall(
         node, node.argumentList.arguments, constructor, this, _errorReporter);
   }
 
   @override
   DartObjectImpl visitIntegerLiteral(IntegerLiteral node) =>
       new DartObjectImpl(_typeProvider.intType, new IntState(node.value));
 
   @override
   DartObjectImpl visitInterpolationExpression(InterpolationExpression node) {
@@ skipping 23 matching lines @@
       if (elementResult == null) {
         errorOccurred = true;
       } else {
         elements.add(elementResult);
       }
     }
     if (errorOccurred) {
       return null;
     }
     DartType elementType = _typeProvider.dynamicType;
-    if (node.typeArguments != null &&
-        node.typeArguments.arguments.length == 1) {
-      DartType type = node.typeArguments.arguments[0].type;
+    NodeList<TypeName> typeArgs = node.typeArguments?.arguments;
+    if (typeArgs?.length == 1) {
+      DartType type = visitTypeName(typeArgs[0]).toTypeValue();
       if (type != null) {
         elementType = type;
       }
     }
     InterfaceType listType = _typeProvider.listType.instantiate([elementType]);
     return new DartObjectImpl(listType, new ListState(elements));
   }
 
   @override
   DartObjectImpl visitMapLiteral(MapLiteral node) {
@@ skipping 12 matching lines @@
         errorOccurred = true;
       } else {
         map[keyResult] = valueResult;
       }
     }
     if (errorOccurred) {
       return null;
     }
     DartType keyType = _typeProvider.dynamicType;
     DartType valueType = _typeProvider.dynamicType;
-    if (node.typeArguments != null &&
-        node.typeArguments.arguments.length == 2) {
-      DartType keyTypeCandidate = node.typeArguments.arguments[0].type;
+    NodeList<TypeName> typeArgs = node.typeArguments?.arguments;
+    if (typeArgs?.length == 2) {
+      DartType keyTypeCandidate = visitTypeName(typeArgs[0]).toTypeValue();
       if (keyTypeCandidate != null) {
         keyType = keyTypeCandidate;
       }
-      DartType valueTypeCandidate = node.typeArguments.arguments[1].type;
+      DartType valueTypeCandidate = visitTypeName(typeArgs[1]).toTypeValue();
       if (valueTypeCandidate != null) {
         valueType = valueTypeCandidate;
       }
     }
     InterfaceType mapType =
         _typeProvider.mapType.instantiate([keyType, valueType]);
     return new DartObjectImpl(mapType, new MapState(map));
   }
 
   @override
@@ skipping 129 matching lines @@
     for (int i = 0; i < components.length; i++) {
       if (i > 0) {
         buffer.writeCharCode(0x2E);
       }
       buffer.write(components[i].lexeme);
     }
     return new DartObjectImpl(
         _typeProvider.symbolType, new SymbolState(buffer.toString()));
   }
 
+  @override
+  DartObjectImpl visitTypeName(TypeName node) {
+    return typeConstant(evaluateType(node.type));
+  }
+
+  /**
+   * Given a [type], returns the constant value that contains that type value.
+   */
+  DartObjectImpl typeConstant(DartType type) {
+    return new DartObjectImpl(_typeProvider.typeType, new TypeState(type));
+  }
+
+  /**
+   * Given a [type] that may contain free type variables, evaluate them against
+   * the current lexical environment and return the substituted type.
+   */
+  DartType evaluateType(DartType type) {
+    if (type is TypeParameterType) {
+      String name = type.name;
+      if (_lexicalEnvironment != null) {
+        return _lexicalEnvironment[name]?.toTypeValue() ?? type;
+      }
+      return type;
+    }
+    if (type is ParameterizedType) {
+      List<DartType> typeArguments;
+      for (int i = 0; i < type.typeArguments.length; i++) {
+        DartType ta = type.typeArguments[i];
+        DartType t = evaluateType(ta);
+        if (!identical(t, ta)) {
+          if (typeArguments == null) {
+            typeArguments = type.typeArguments.toList(growable: false);
+          }
+          typeArguments[i] = t;
+        }
+      }
+      if (typeArguments == null) return type;
+      return type.substitute2(typeArguments, type.typeArguments);
+    }
+    return type;
+  }
+
   /**
    * Create an error associated with the given [node]. The error will have the
    * given error [code].
    */
   void _error(AstNode node, ErrorCode code) {
     _errorReporter.reportErrorForNode(
         code ?? CompileTimeErrorCode.INVALID_CONSTANT, node);
   }
 
   /**
@@ skipping 12 matching lines @@
       }
     } else if (variableElement is ExecutableElement) {
       ExecutableElement function = element;
       if (function.isStatic) {
         ParameterizedType functionType = function.type;
         if (functionType == null) {
           functionType = _typeProvider.functionType;
         }
         return new DartObjectImpl(functionType, new FunctionState(function));
       }
-    } else if (variableElement is ClassElement ||
-        variableElement is FunctionTypeAliasElement ||
-        variableElement is DynamicElementImpl) {
-      return new DartObjectImpl(_typeProvider.typeType, new TypeState(element));
+    } else if (variableElement is TypeDefiningElement) {
+      return new DartObjectImpl(
+          _typeProvider.typeType, new TypeState(variableElement.type));
     }
     // TODO(brianwilkerson) Figure out which error to report.
     _error(node, null);
     return null;
   }
 
   /**
    * Return `true` if the given [targetResult] represents a string and the
    * [identifier] is "length".
    */
@@ skipping 470 matching lines @@
   }
 
   @override
   String toString() {
     if (value == null) {
       return "error";
     }
     return value.toString();
   }
 }