[cfe][InternalNodes] Add AuxiliaryPattern

This allows for creating internal pattern nodes in the CFE.

Change-Id: Ifad3c29eb7dd329ecd902c7b43fcff58ad862bcc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/508000
Commit-Queue: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>

pkg/front_end/lib/src/type_inference/inference_visitor.dart

@@ -926,6 +926,16 @@ class InferenceVisitorImpl extends InferenceVisitorBase
     );
   }
 
+  // Coverage-ignore(suite): Not run.
+  Never _unhandledPattern(Pattern node) {
+    problems.unhandled(
+      "${node.runtimeType}",
+      "InferenceVisitor",
+      node.fileOffset,
+      node.location!.file,
+    );
+  }
+
   @override
   InitializerInferenceResult visitInvalidInitializer(InvalidInitializer node) {
     return new SuccessfulInitializerInferenceResult(node);
@@ -16486,6 +16496,15 @@ class InferenceVisitorImpl extends InferenceVisitorBase
     return _unhandledInitializer(node);
   }
 
+  @override
+  // Coverage-ignore(suite): Not run.
+  PatternResult visitAuxiliaryPattern(
+    AuxiliaryPattern node,
+    SharedMatchContext context,
+  ) {
+    return _unhandledPattern(node);
+  }
+
   @override
   // Coverage-ignore(suite): Not run.
   StatementInferenceResult visitAuxiliaryStatement(AuxiliaryStatement node) {

pkg/front_end/lib/src/type_inference/matching_expressions.dart

@@ -938,4 +938,14 @@ class MatchingExpressionVisitor
       return new BooleanExpression(true, fileOffset: node.fileOffset);
     }
   }
+
+  @override
+  DelayedExpression visitAuxiliaryPattern(
+    AuxiliaryPattern node,
+    CacheableExpression matchedExpression,
+  ) {
+    throw new UnsupportedError(
+      "Unexpected pattern $node (${node.runtimeType}).",
+    );
+  }
 }

pkg/kernel/lib/binary/ast_to_binary.dart

@@ -3188,6 +3188,13 @@ class BinaryPrinter
     );
   }
 
+  @override
+  void visitAuxiliaryPattern(AuxiliaryPattern node) {
+    throw new UnsupportedError(
+      'serialization of auxiliary Pattern: ${node} (${node.runtimeType})',
+    );
+  }
+
   @override
   void visitBoolConstant(BoolConstant node) {
     throw new UnsupportedError('serialization of BoolConstants');

pkg/kernel/lib/clone.dart

@@ -1374,6 +1374,13 @@ class CloneVisitorNotMembers
       "Unsupported auxiliary initializer ${node} (${node.runtimeType}).",
     );
   }
+
+  @override
+  TreeNode visitAuxiliaryPattern(AuxiliaryPattern node) {
+    throw new UnsupportedError(
+      "Unsupported auxiliary pattern ${node} (${node.runtimeType}).",
+    );
+  }
 }
 
 /// Visitor that return a clone of a tree, maintaining references to cloned

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

@@ -1485,6 +1485,17 @@ class InvalidPattern extends Pattern {
   }
 }
 
+/// Abstract subclass of [Pattern] that can be used to add [Pattern]
+/// subclasses from outside `package:kernel`.
+abstract class AuxiliaryPattern extends Pattern {
+  @override
+  R accept<R>(PatternVisitor<R> v) => v.visitAuxiliaryPattern(this);
+
+  @override
+  R accept1<R, A>(PatternVisitor1<R, A> v, A arg) =>
+      v.visitAuxiliaryPattern(this, arg);
+}
+
 class MapPatternEntry extends TreeNode {
   Expression key;
   Pattern value;

pkg/kernel/lib/src/coverage.dart

@@ -792,6 +792,13 @@ class CoverageVisitor implements Visitor<void> {
     node.visitChildren(this);
   }
 
+  @override
+  void visitAuxiliaryPattern(AuxiliaryPattern node) {
+    throw new UnsupportedError(
+      "Unsupported auxiliary node $node (${node.runtimeType}).",
+    );
+  }
+
   @override
   void visitMapPatternEntry(MapPatternEntry node) {
     visited.add(NodeKind.MapPatternEntry);

pkg/kernel/lib/src/equivalence.dart

@@ -699,6 +699,11 @@ class EquivalenceVisitor implements Visitor1<bool, Node> {
     return strategy.checkInvalidPattern(this, node, other);
   }
 
+  @override
+  bool visitAuxiliaryPattern(AuxiliaryPattern node, Node other) {
+    return strategy.checkAuxiliaryPattern(this, node, other);
+  }
+
   @override
   bool visitMapPatternEntry(MapPatternEntry node, Node other) {
     return strategy.checkMapPatternEntry(this, node, other);
@@ -5214,6 +5219,23 @@ class EquivalenceStrategy {
     return result;
   }
 
+  bool checkAuxiliaryPattern(
+    EquivalenceVisitor visitor,
+    AuxiliaryPattern? node,
+    Object? other,
+  ) {
+    if (identical(node, other)) return true;
+    if (node is! AuxiliaryPattern) return false;
+    if (other is! AuxiliaryPattern) return false;
+    visitor.pushNodeState(node, other);
+    bool result = true;
+    if (!checkAuxiliaryPattern_fileOffset(visitor, node, other)) {
+      result = visitor.resultOnInequivalence;
+    }
+    visitor.popState();
+    return result;
+  }
+
   bool checkMapPatternEntry(
     EquivalenceVisitor visitor,
     MapPatternEntry? node,
@@ -12380,6 +12402,14 @@ class EquivalenceStrategy {
     return checkPattern_fileOffset(visitor, node, other);
   }
 
+  bool checkAuxiliaryPattern_fileOffset(
+    EquivalenceVisitor visitor,
+    AuxiliaryPattern node,
+    AuxiliaryPattern other,
+  ) {
+    return checkPattern_fileOffset(visitor, node, other);
+  }
+
   bool checkMapPatternEntry_key(
     EquivalenceVisitor visitor,
     MapPatternEntry node,

pkg/kernel/lib/visitor.dart

@@ -262,6 +262,7 @@ abstract class PatternVisitor<R> {
   R visitRestPattern(RestPattern node);
   R visitVariablePattern(VariablePattern node);
   R visitWildcardPattern(WildcardPattern node);
+  R visitAuxiliaryPattern(AuxiliaryPattern node);
 }
 
 /// Helper mixin for [PatternVisitor] that implements visit methods by
@@ -304,198 +305,8 @@ mixin PatternVisitorDefaultMixin<R> implements PatternVisitor<R> {
   R visitVariablePattern(VariablePattern node) => defaultPattern(node);
   @override
   R visitWildcardPattern(WildcardPattern node) => defaultPattern(node);
-}
-
-/// [PatternVisitorInternalNodeMixin] is intended to reduce the effects of
-/// CFE internal nodes on the backends.
-///
-/// The mixin provides implementations of the visit methods for the internal
-/// nodes that are not expected to be part of AST delivered to backends. The
-/// methods throw an exception signaling that the internal nodes aren't
-/// supported.
-mixin PatternVisitorInternalNodeMixin<R> implements PatternVisitor<R> {
   @override
-  R visitAndPattern(AndPattern node) {
-    throw StateError("${runtimeType}.visitAndPattern isn't supported.");
-  }
-
-  @override
-  R visitAssignedVariablePattern(AssignedVariablePattern node) {
-    throw StateError(
-      "${runtimeType}.visitAssignedVariablePattern isn't supported.",
-    );
-  }
-
-  @override
-  R visitCastPattern(CastPattern node) {
-    throw StateError("${runtimeType}.visitCastPattern isn't supported.");
-  }
-
-  @override
-  R visitConstantPattern(ConstantPattern node) {
-    throw StateError("${runtimeType}.visitConstantPattern isn't supported.");
-  }
-
-  @override
-  R visitInvalidPattern(InvalidPattern node) {
-    throw StateError("${runtimeType}.visitInvalidPattern isn't supported.");
-  }
-
-  @override
-  R visitListPattern(ListPattern node) {
-    throw StateError("${runtimeType}.visitListPattern isn't supported.");
-  }
-
-  @override
-  R visitMapPattern(MapPattern node) {
-    throw StateError("${runtimeType}.visitMapPattern isn't supported.");
-  }
-
-  @override
-  R visitNamedPattern(NamedPattern node) {
-    throw StateError("${runtimeType}.visitNamedPattern isn't supported.");
-  }
-
-  @override
-  R visitNullAssertPattern(NullAssertPattern node) {
-    throw StateError("${runtimeType}.visitNullAssertPattern isn't supported.");
-  }
-
-  @override
-  R visitNullCheckPattern(NullCheckPattern node) {
-    throw StateError("${runtimeType}.visitNullCheckPattern isn't supported.");
-  }
-
-  @override
-  R visitObjectPattern(ObjectPattern node) {
-    throw StateError("${runtimeType}.visitObjectPattern isn't supported.");
-  }
-
-  @override
-  R visitOrPattern(OrPattern node) {
-    throw StateError("${runtimeType}.visitOrPattern isn't supported.");
-  }
-
-  @override
-  R visitRecordPattern(RecordPattern node) {
-    throw StateError("${runtimeType}.visitRecordPattern isn't supported.");
-  }
-
-  @override
-  R visitRelationalPattern(RelationalPattern node) {
-    throw StateError("${runtimeType}.visitRelationalPattern isn't supported.");
-  }
-
-  @override
-  R visitRestPattern(RestPattern node) {
-    throw StateError("${runtimeType}.visitRestPattern isn't supported.");
-  }
-
-  @override
-  R visitVariablePattern(VariablePattern node) {
-    throw StateError("${runtimeType}.visitVariablePattern isn't supported.");
-  }
-
-  @override
-  R visitWildcardPattern(WildcardPattern node) {
-    throw StateError("${runtimeType}.visitWildcardPattern isn't supported.");
-  }
-}
-
-/// [PatternVisitor1InternalNodeMixin] is intended to reduce the effects of
-/// CFE internal nodes on the backends.
-///
-/// The mixin provides implementations of the visit methods for the internal
-/// nodes that are not expected to be part of AST delivered to backends. The
-/// methods throw an exception signaling that the internal nodes aren't
-/// supported.
-mixin PatternVisitor1InternalNodeMixin<R, A> implements PatternVisitor1<R, A> {
-  @override
-  R visitAndPattern(AndPattern node, A arg) {
-    throw StateError("${runtimeType}.visitAndPattern isn't supported.");
-  }
-
-  @override
-  R visitAssignedVariablePattern(AssignedVariablePattern node, A arg) {
-    throw StateError(
-      "${runtimeType}.visitAssignedVariablePattern isn't supported.",
-    );
-  }
-
-  @override
-  R visitCastPattern(CastPattern node, A arg) {
-    throw StateError("${runtimeType}.visitCastPattern isn't supported.");
-  }
-
-  @override
-  R visitConstantPattern(ConstantPattern node, A arg) {
-    throw StateError("${runtimeType}.visitConstantPattern isn't supported.");
-  }
-
-  @override
-  R visitInvalidPattern(InvalidPattern node, A arg) {
-    throw StateError("${runtimeType}.visitInvalidPattern isn't supported.");
-  }
-
-  @override
-  R visitListPattern(ListPattern node, A arg) {
-    throw StateError("${runtimeType}.visitListPattern isn't supported.");
-  }
-
-  @override
-  R visitMapPattern(MapPattern node, A arg) {
-    throw StateError("${runtimeType}.visitMapPattern isn't supported.");
-  }
-
-  @override
-  R visitNamedPattern(NamedPattern node, A arg) {
-    throw StateError("${runtimeType}.visitNamedPattern isn't supported.");
-  }
-
-  @override
-  R visitNullAssertPattern(NullAssertPattern node, A arg) {
-    throw StateError("${runtimeType}.visitNullAssertPattern isn't supported.");
-  }
-
-  @override
-  R visitNullCheckPattern(NullCheckPattern node, A arg) {
-    throw StateError("${runtimeType}.visitNullCheckPattern isn't supported.");
-  }
-
-  @override
-  R visitObjectPattern(ObjectPattern node, A arg) {
-    throw StateError("${runtimeType}.visitObjectPattern isn't supported.");
-  }
-
-  @override
-  R visitOrPattern(OrPattern node, A arg) {
-    throw StateError("${runtimeType}.visitOrPattern isn't supported.");
-  }
-
-  @override
-  R visitRecordPattern(RecordPattern node, A arg) {
-    throw StateError("${runtimeType}.visitRecordPattern isn't supported.");
-  }
-
-  @override
-  R visitRelationalPattern(RelationalPattern node, A arg) {
-    throw StateError("${runtimeType}.visitRelationalPattern isn't supported.");
-  }
-
-  @override
-  R visitRestPattern(RestPattern node, A arg) {
-    throw StateError("${runtimeType}.visitRestPattern isn't supported.");
-  }
-
-  @override
-  R visitVariablePattern(VariablePattern node, A arg) {
-    throw StateError("${runtimeType}.visitVariablePattern isn't supported.");
-  }
-
-  @override
-  R visitWildcardPattern(WildcardPattern node, A arg) {
-    throw StateError("${runtimeType}.visitWildcardPattern isn't supported.");
-  }
+  R visitAuxiliaryPattern(AuxiliaryPattern node) => defaultPattern(node);
 }
 
 abstract class StatementVisitor<R> {
@@ -2811,6 +2622,7 @@ abstract class PatternVisitor1<R, A> {
   R visitRestPattern(RestPattern node, A arg);
   R visitVariablePattern(VariablePattern node, A arg);
   R visitWildcardPattern(WildcardPattern node, A arg);
+  R visitAuxiliaryPattern(AuxiliaryPattern node, A arg);
 }
 
 /// Helper mixin for [PatternVisitor1] that implements visit methods by
@@ -2859,6 +2671,9 @@ mixin PatternVisitor1DefaultMixin<R, A> implements PatternVisitor1<R, A> {
   @override
   R visitWildcardPattern(WildcardPattern node, A arg) =>
       defaultPattern(node, arg);
+  @override
+  R visitAuxiliaryPattern(AuxiliaryPattern node, A arg) =>
+      defaultPattern(node, arg);
 }
 
 abstract class StatementVisitor1<R, A> {