Elements. Make PropertyAccessorElement.variable non-nullable.

The null assert in `PropertyAccessorElementImpl.variable` is safe
because `ElementBuilder` always creates synthetic
`TopLevelVariableFragmentImpl` or `FieldElementImpl` for a getter or
setter. And the other way around, non-synthetic
`TopLevelVariableFragmentImpl` or `FieldElementImpl` when created
associate itself with synthetic getter / setter.

Change-Id: I40e4ce866edffab6c8bcdf6e408bd1bbfbba6581
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/442246
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Paul Berry <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analysis_server/lib/src/cider/local_library_contributor.dart

@@ -101,9 +101,7 @@ class LibraryElementSuggestionBuilder
   void visitGetterElement(GetterElement element) {
     var variable = element.variable;
     if (opType.includeReturnValueSuggestions ||
-        (opType.includeAnnotationSuggestions &&
-            variable != null &&
-            variable.isConst)) {
+        (opType.includeAnnotationSuggestions && variable.isConst)) {
       var parent = element.enclosingElement;
       if (parent is InterfaceElement || parent is ExtensionElement) {
         if (element.isSynthetic) {
@@ -140,9 +138,7 @@ class LibraryElementSuggestionBuilder
   void visitSetterElement(SetterElement element) {
     var variable = element.variable;
     if (opType.includeReturnValueSuggestions ||
-        (opType.includeAnnotationSuggestions &&
-            variable != null &&
-            variable.isConst)) {
+        (opType.includeAnnotationSuggestions && variable.isConst)) {
       var parent = element.enclosingElement;
       if (parent is InterfaceElement || parent is ExtensionElement) {
         if (!element.isSynthetic) {

pkg/analysis_server/lib/src/cider/rename.dart

@@ -437,9 +437,6 @@ class CiderRenameComputer {
     }
     if (element is PropertyAccessorElement) {
       element = element.variable;
-      if (element == null) {
-        return null;
-      }
     }
     if (!_canRenameElement(element)) {
       return null;

pkg/analysis_server/lib/src/computer/computer_documentation.dart

@@ -33,7 +33,7 @@ class DartDocumentationComputer {
       element,
       ...overridden.superElements,
       ...overridden.interfaceElements,
-      if (element case PropertyAccessorElement(:var variable?)) variable,
+      if (element case PropertyAccessorElement(:var variable)) variable,
     ];
     for (var candidate in candidates) {
       if (candidate.documentationCommentOrNull != null) {

pkg/analysis_server/lib/src/domains/analysis/occurrences_dart.dart

@@ -400,7 +400,7 @@ class DartUnitOccurrencesComputerVisitor extends GeneralizingAstVisitor<void> {
     if (canonicalElement is FieldFormalParameterElement) {
       canonicalElement = canonicalElement.field;
     } else if (canonicalElement case PropertyAccessorElement(
-      :var variable?,
+      :var variable,
     ) when !variable.isSynthetic) {
       canonicalElement = variable;
     }

pkg/analysis_server/lib/src/lsp/handlers/custom/handler_summary.dart

@@ -75,10 +75,10 @@ class SummaryWriter {
     for (var element in definedNames.values) {
       if (element.isSynthetic) {
         if (element is GetterElement) {
-          element = element.variable!;
+          element = element.variable;
         } else if (element is SetterElement &&
             element.correspondingGetter == null) {
-          element = element.variable!;
+          element = element.variable;
         } else {
           continue;
         }

pkg/analysis_server/lib/src/lsp/handlers/handler_document_color_presentation.dart

@@ -249,7 +249,7 @@ class DocumentColorPresentationHandler
           parent is PrefixedIdentifier ? parent.element : node.element;
 
       return switch (element) {
-        PropertyAccessorElement(:var variable) => variable?.isConst ?? false,
+        PropertyAccessorElement(:var variable) => variable.isConst,
         VariableElement() => element.isConst,
         _ => false,
       };

pkg/analysis_server/lib/src/lsp/handlers/handler_references.dart

@@ -69,7 +69,7 @@ class ReferencesHandler
 
     var element = switch (node?.getElement()) {
       FieldFormalParameterElement(:var field?) => field,
-      PropertyAccessorElement(:var variable?) => variable,
+      PropertyAccessorElement(:var variable) => variable,
       var element => element,
     };
 

pkg/analysis_server/lib/src/lsp/handlers/handler_type_definition.dart

@@ -217,7 +217,7 @@ class TypeDefinitionHandler
         if (writeElement
             case analyzer.GetterElement(:var variable) ||
                 analyzer.SetterElement(:var variable)) {
-          return variable?.type;
+          return variable.type;
         }
       }
     }

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

@@ -2723,9 +2723,7 @@ extension on PropertyAccessorElement {
   /// Whether this accessor is an accessor for a constant variable.
   bool get isConst {
     if (isSynthetic) {
-      if (variable case var variable?) {
-        return variable.isConst;
-      }
+      return variable.isConst;
     }
     return false;
   }

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

@@ -199,11 +199,7 @@ class FeatureComputer {
     } else if (element is FieldElement && element.isEnumConstant) {
       return protocol.ElementKind.ENUM_CONSTANT;
     } else if (element is PropertyAccessorElement) {
-      var variable = element.variable;
-      if (variable == null) {
-        return protocol.ElementKind.UNKNOWN;
-      }
-      element = variable;
+      element = element.variable;
     }
     var kind = element.kind;
     if (kind == ElementKind.CONSTRUCTOR) {
@@ -255,11 +251,7 @@ class FeatureComputer {
     } else if (element is FieldElement && element.isEnumConstant) {
       return protocol.ElementKind.ENUM_CONSTANT;
     } else if (element is PropertyAccessorElement) {
-      var variable = element.variable;
-      if (variable == null) {
-        return protocol.ElementKind.UNKNOWN;
-      }
-      element = variable;
+      element = element.variable;
     }
     var kind = element.kind;
     if (kind == ElementKind.CONSTRUCTOR) {
@@ -392,7 +384,7 @@ class FeatureComputer {
       return 1.0;
     } else if (element is PropertyAccessorElement && element.isSynthetic) {
       var variable = element.variable;
-      if (variable != null && variable.isStatic && variable.isConst) {
+      if (variable.isStatic && variable.isConst) {
         return 1.0;
       }
     }