Elements. Exploit the fact that setters always have exctly one formal parameter.

So, it is always present in the AST.
And it is always present in the elements model: fragments and elements.

Change-Id: I8ca84f88d4a605f926008c1c2d638cb48e4d26f5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/442104
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Paul Berry <[email protected]>

Author: scheglov

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

@@ -5132,7 +5132,8 @@ abstract class InterfaceFragmentImpl extends InstanceFragmentImpl
   List<InterfaceTypeImpl> _interfaces = const [];
 
   /// This callback is set during mixins inference to handle reentrant calls.
-  List<InterfaceTypeImpl>? Function(InterfaceFragmentImpl)? mixinInferenceCallback;
+  List<InterfaceTypeImpl>? Function(InterfaceFragmentImpl)?
+  mixinInferenceCallback;
 
   InterfaceTypeImpl? _supertype;
 
@@ -8735,8 +8736,7 @@ abstract class PropertyInducingElementImpl extends VariableElementImpl
     if (element.setter case var setterElement?) {
       if (setterElement.isSynthetic) {
         setterElement.returnType = VoidTypeImpl.instance;
-        setterElement.formalParameters.single
-            .type = type;
+        setterElement.valueFormalParameter.type = type;
       }
     }
 
@@ -8963,8 +8963,8 @@ class SetterFragmentImpl extends PropertyAccessorFragmentImpl
     return null;
   }
 
-  FormalParameterFragmentImpl? get valueFormalParameter {
-    return formalParameters.singleOrNull;
+  FormalParameterFragmentImpl get valueFormalParameter {
+    return formalParameters.single;
   }
 
   void addFragment(SetterFragmentImpl fragment) {

pkg/analyzer/lib/src/fine/manifest_item.dart

@@ -761,7 +761,7 @@ class InstanceItemSetterItem extends InstanceItemMemberItem<SetterElementImpl> {
         element.thisOrVariableMetadata,
       ),
       isStatic: element.isStatic,
-      valueType: element.formalParameters[0].type.encode(context),
+      valueType: element.valueFormalParameter.type.encode(context),
     );
   }
 
@@ -777,7 +777,7 @@ class InstanceItemSetterItem extends InstanceItemMemberItem<SetterElementImpl> {
   @override
   bool match(MatchContext context, SetterElementImpl element) {
     return super.match(context, element) &&
-        valueType.match(context, element.formalParameters[0].type);
+        valueType.match(context, element.valueFormalParameter.type);
   }
 
   @override
@@ -1302,7 +1302,7 @@ class TopLevelSetterItem extends TopLevelItem<SetterElementImpl> {
         context,
         element.thisOrVariableMetadata,
       ),
-      valueType: element.formalParameters[0].type.encode(context),
+      valueType: element.valueFormalParameter.type.encode(context),
     );
   }
 
@@ -1317,7 +1317,7 @@ class TopLevelSetterItem extends TopLevelItem<SetterElementImpl> {
   @override
   bool match(MatchContext context, SetterElementImpl element) {
     return super.match(context, element) &&
-        valueType.match(context, element.formalParameters[0].type);
+        valueType.match(context, element.valueFormalParameter.type);
   }
 
   @override

pkg/analyzer/lib/src/summary2/bundle_reader.dart

@@ -1115,13 +1115,6 @@ class LibraryReader {
 
       element.deferReadResolution(
         _createDeferredReadResolutionCallback((reader) {
-          // TODO(scheglov): add to element
-          var valueFragment = fragments.first.valueFormalParameter;
-          if (valueFragment != null) {
-            // TODO(scheglov): create, not get
-            valueFragment.element;
-          }
-
           element.returnType = reader.readRequiredType();
           // TODO(scheglov): other properties?
         }),

pkg/analyzer/lib/src/summary2/instance_member_inferrer.dart

@@ -206,12 +206,7 @@ class InstanceMemberInferrer {
     }
 
     if (setter != null) {
-      var formalParameters =
-          setter.formalParameters.cast<FormalParameterElementImpl>();
-      if (formalParameters.isEmpty) {
-        return;
-      }
-      var valueFormalParameter = formalParameters[0];
+      var valueFormalParameter = setter.valueFormalParameter;
 
       if (overriddenSetters.any((s) => _isCovariantSetter(s.baseElement))) {
         valueFormalParameter.inheritsCovariant = true;
@@ -258,9 +253,7 @@ class InstanceMemberInferrer {
       var setter = field.setter;
       if (setter != null) {
         if (overriddenSetters.any((s) => _isCovariantSetter(s.baseElement))) {
-          var formalParameter = setter.formalParameters[0];
-          formalParameter.inheritsCovariant =
-              true;
+          setter.valueFormalParameter.inheritsCovariant = true;
         }
       }
 
@@ -491,11 +484,7 @@ class InstanceMemberInferrer {
     var formalParameters = element.formalParameters;
     for (var index = 0; index < formalParameters.length; index++) {
       var formalParameter = formalParameters[index];
-      _inferParameterCovariance(
-        formalParameter,
-        index,
-        overriddenElements,
-      );
+      _inferParameterCovariance(formalParameter, index, overriddenElements);
 
       if (formalParameter.hasImplicitType) {
         _inferParameterType(formalParameter, index, combinedSignatureType);
@@ -757,10 +746,7 @@ class InstanceMemberInferrer {
       return overriddenType;
     }
 
-    return replaceTypeParameters(
-      overriddenType,
-      elementTypeParameters,
-    );
+    return replaceTypeParameters(overriddenType, elementTypeParameters);
   }
 
   static bool _isCovariantSetter(ExecutableElementImpl element) {

pkg/analyzer/lib/src/summary2/types_builder.dart

@@ -186,14 +186,11 @@ class TypesBuilder {
           (element.variable as TopLevelVariableElementImpl).type = returnType;
         case SetterElementImpl():
           element.returnType = returnType;
-          var valueElement =
-              element.formalParameters.singleOrNull;
-          var valueNode =
-              node.functionExpression.parameters?.parameters.firstOrNull;
-          var valueNodeElement = valueNode?.declaredFragment!.element;
-          var valueNodeType = valueNodeElement?.type;
-          var valueType = valueNodeType ?? InvalidTypeImpl.instance;
-          valueElement?.type = valueType;
+          var valueElement = element.valueFormalParameter;
+          var valueNode = node.functionExpression.parameters!.parameters.single;
+          var valueNodeElement = valueNode.declaredFragment!.element;
+          var valueType = valueNodeElement.type;
+          valueElement.type = valueType;
 
           var variableElement = element.variable as TopLevelVariableElementImpl;
           if (variableElement.isSynthetic) {
@@ -229,13 +226,11 @@ class TypesBuilder {
           (element.variable as FieldElementImpl).type = returnType;
         case SetterElementImpl():
           element.returnType = returnType;
-          var valueElement =
-              element.formalParameters.singleOrNull;
-          var valueNode = node.parameters?.parameters.firstOrNull;
-          var valueNodeElement = valueNode?.declaredFragment!.element;
-          var valueNodeType = valueNodeElement?.type;
-          var valueType = valueNodeType ?? InvalidTypeImpl.instance;
-          valueElement?.type = valueType;
+          var valueElement = element.valueFormalParameter;
+          var valueNode = node.parameters!.parameters.single;
+          var valueNodeElement = valueNode.declaredFragment!.element;
+          var valueType = valueNodeElement.type;
+          valueElement.type = valueType;
 
           var variableElement = element.variable as FieldElementImpl;
           if (variableElement.isSynthetic && variableElement.getter == null) {
@@ -266,8 +261,7 @@ class TypesBuilder {
             }
             if (variableElement.setter case var setterElement?) {
               setterElement.returnType = VoidTypeImpl.instance;
-              setterElement.formalParameters.single
-                  .type = type;
+              setterElement.valueFormalParameter.type = type;
             }
           }
         }
@@ -648,7 +642,9 @@ class _MixinsInference {
 
   /// This method is invoked when mixins are asked from the [element], and
   /// we are not inferring the [element] now, i.e. there is no loop.
-  List<InterfaceTypeImpl>? _callbackWhenRecursion(InterfaceFragmentImpl element) {
+  List<InterfaceTypeImpl>? _callbackWhenRecursion(
+    InterfaceFragmentImpl element,
+  ) {
     var declaration = _declarations[element];
     if (declaration != null) {
       _inferDeclaration(declaration);