[cfe][InternalNodes] Implement InternalVariable directly

This updates the InternalVariable hierarchy to be based on a sealed base class InternalVariable with no connection to IVariable. IVariable is removed and unused properties of InternalVariable are removed.

TEST=existing

Change-Id: Iacfbe9ab21d1c9aab043712099cd1ee6e4cee174
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/510825
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Nicholas Shahan <nshahan@google.com>
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Commit-Queue: Johnni Winther <johnniwinther@google.com>

pkg/kernel/lib/src/ast/variables.dart

@@ -21,15 +21,20 @@ sealed class VariableBase extends TreeNode implements Annotatable {
   }
 }
 
-/// This is a helper class to enable mixing a mixin into concrete
-/// implementations of the sealed class [Variable]. It's not supposed
-/// to be used as a type annotation, but purely for declaring the class
-/// hierarchy.
-abstract interface class IVariable implements TreeNode, Annotatable {
+/// The root of the sealed hierarchy of non-type variables.
+sealed class Variable extends VariableBase implements ContextConsumer {
+  /// Static type of the variable.
   abstract DartType type;
-  abstract String? cosmeticName;
+
+  /// Declaration node for the variable, if available.
   abstract VariableDeclaration? variableDeclaration;
+
+  /// Derived from [variableDeclaration], if available.
   abstract Expression? initializer;
+
+  @override
+  abstract List<Expression> annotations;
+
   abstract bool isFinal;
   abstract bool isConst;
   abstract bool isLate;
@@ -48,78 +53,9 @@ abstract interface class IVariable implements TreeNode, Annotatable {
   // The following is due to [VariableDeclaration] implementing
   // [VariableInitialization].
   abstract int binaryOffsetNoTag;
-  abstract List<VariableContext>? capturedContexts;
   abstract int fileEqualsOffset;
-  abstract Variable variable;
   void clearAnnotations();
 
-  VariableContext? get context;
-  void set context(VariableContext value);
-
-  bool get isAssignable;
-  bool get hasIsFinal;
-  bool get hasIsConst;
-  bool get hasIsLate;
-  bool get hasIsInitializingFormal;
-  bool get hasIsSynthesized;
-  bool get hasIsHoisted;
-  bool get hasHasDeclaredInitializer;
-  bool get hasIsCovariantByClass;
-  bool get hasIsRequired;
-  bool get hasIsCovariantByDeclaration;
-  bool get hasIsLowered;
-  bool get hasIsWildcard;
-  bool get hasIsSuperInitializingFormal;
-  bool get hasIsErroneouslyInitialized;
-}
-
-/// The root of the sealed hierarchy of non-type variables.
-sealed class Variable extends VariableBase
-    implements IVariable, ContextConsumer {
-  /// Static type of the variable.
-  @override
-  abstract DartType type;
-
-  /// Declaration node for the variable, if available.
-  @override
-  abstract VariableDeclaration? variableDeclaration;
-
-  /// Derived from [variableDeclaration], if available.
-  @override
-  abstract Expression? initializer;
-
-  @override
-  abstract List<Expression> annotations;
-
-  @override
-  abstract bool isFinal;
-  @override
-  abstract bool isConst;
-  @override
-  abstract bool isLate;
-  @override
-  abstract bool isInitializingFormal;
-  @override
-  abstract bool isSynthesized;
-  @override
-  abstract bool isHoisted;
-  @override
-  abstract bool hasDeclaredInitializer;
-  @override
-  abstract bool isCovariantByClass;
-  @override
-  abstract bool isRequired;
-  @override
-  abstract bool isCovariantByDeclaration;
-  @override
-  abstract bool isLowered;
-  @override
-  abstract bool isWildcard;
-  @override
-  abstract bool isSuperInitializingFormal;
-  @override
-  abstract bool isErroneouslyInitialized;
-
   factory(
     String? name, {
     Expression? initializer,
@@ -153,36 +89,21 @@ sealed class Variable extends VariableBase
 
   new empty();
 
-  @override
   bool get hasIsFinal;
-  @override
   bool get hasIsConst;
-  @override
   bool get hasIsLate;
-  @override
   bool get hasIsInitializingFormal;
-  @override
   bool get hasIsSynthesized;
-  @override
   bool get hasIsHoisted;
-  @override
   bool get hasHasDeclaredInitializer;
-  @override
   bool get hasIsCovariantByClass;
-  @override
   bool get hasIsRequired;
-  @override
   bool get hasIsCovariantByDeclaration;
-  @override
   bool get hasIsLowered;
-  @override
   bool get hasIsWildcard;
-  @override
   bool get hasIsSuperInitializingFormal;
-  @override
   bool get hasIsErroneouslyInitialized;
 
-  @override
   bool get isAssignable;
 
   abstract String? name;
@@ -642,14 +563,6 @@ class LegacyVariable extends TreeNode implements Variable, Annotatable {
     throw new UnsupportedError("${this.runtimeType}.context=");
   }
 
-  @override
-  Variable get variable => this;
-
-  @override
-  void set variable(Variable value) {
-    throw new UnsupportedError("${this.runtimeType}.variable=");
-  }
-
   @override
   bool get hasHasDeclaredInitializer => true;
 
@@ -989,14 +902,6 @@ class LocalVariable extends Variable {
   @override
   int fileEqualsOffset = TreeNode.noOffset;
 
-  @override
-  Variable get variable => this;
-
-  @override
-  void set variable(Variable variable) {
-    throw new UnsupportedError("${this.runtimeType}.variable=");
-  }
-
   @override
   void clearAnnotations() {
     annotations.clear();
@@ -1302,14 +1207,6 @@ class LateVariable extends Variable {
   @override
   int fileEqualsOffset = TreeNode.noOffset;
 
-  @override
-  Variable get variable => this;
-
-  @override
-  void set variable(Variable variable) {
-    throw new UnsupportedError("${this.runtimeType}.variable=");
-  }
-
   @override
   void clearAnnotations() {
     annotations.clear();
@@ -1618,14 +1515,6 @@ class CatchVariable extends Variable {
   @override
   int fileEqualsOffset = TreeNode.noOffset;
 
-  @override
-  Variable get variable => this;
-
-  @override
-  void set variable(Variable variable) {
-    throw new UnsupportedError("${this.runtimeType}.variable=");
-  }
-
   @override
   void clearAnnotations() {
     annotations.clear();
@@ -1976,14 +1865,6 @@ class PositionalParameter extends FunctionParameter {
 
   @override
   int fileEqualsOffset = TreeNode.noOffset;
-
-  @override
-  Variable get variable => this;
-
-  @override
-  void set variable(Variable value) {
-    throw new UnsupportedError("${this.runtimeType}");
-  }
 }
 
 /// Named parameters. The [name] field is mandatory.
@@ -2129,14 +2010,6 @@ class NamedParameter extends FunctionParameter {
   void set name(String? value) {
     parameterName = value!;
   }
-
-  @override
-  Variable get variable => this;
-
-  @override
-  void set variable(Variable value) {
-    throw new UnsupportedError("${this.runtimeType}");
-  }
 }
 
 /// The variable storage for `this`.
@@ -2409,14 +2282,6 @@ class ThisVariable extends Variable {
   @override
   int fileEqualsOffset = TreeNode.noOffset;
 
-  @override
-  Variable get variable => this;
-
-  @override
-  void set variable(Variable variable) {
-    throw new UnsupportedError("${this.runtimeType}.variable=");
-  }
-
   @override
   void clearAnnotations() {
     annotations.clear();
@@ -2702,14 +2567,6 @@ class SyntheticVariable extends Variable {
   @override
   int fileEqualsOffset = TreeNode.noOffset;
 
-  @override
-  Variable get variable => this;
-
-  @override
-  void set variable(Variable variable) {
-    throw new UnsupportedError("${this.runtimeType}.variable=");
-  }
-
   @override
   void clearAnnotations() {
     annotations.clear();

pkg/kernel/lib/src/printer.dart

@@ -573,7 +573,7 @@ class AstPrinter {
         _sb.write(' ');
       }
     }
-    _sb.write(getVariableName(node.variable));
+    _sb.write(getVariableName(node));
     if (includeInitializer && node.initializer != null && !node.isRequired) {
       _sb.write(' = ');
       writeExpression(node.initializer!);

pkg/kernel/lib/text/ast_to_text.dart

@@ -2867,7 +2867,7 @@ class Printer extends VisitorDefault<void> with VisitorVoidMixin {
           'has-no-declared-initializer',
         );
       }
-      writeWord(getVariableName(variable.variable));
+      writeWord(getVariableName(variable));
       Expression? initializer = variable.initializer;
       if (initializer != null) {
         writeSpaced(':=');

pkg/kernel/lib/verifier.dart

@@ -1277,7 +1277,7 @@ class VerifyingVisitor extends RecursiveResultVisitor<void> {
   void _verifyVariableDeclaration(Variable node) {
     enterTreeNode(node);
     visitChildren(node);
-    declareVariable(node.variable);
+    declareVariable(node);
     if (afterConst && node.isConst && constantLocalsShouldBeRemoved) {
       Expression? initializer = node.initializer;
       if (!(initializer is InvalidExpression ||