Add Vector type to Kernel

pkg/kernel/lib/ast.dart

Index: pkg/kernel/lib/ast.dart
diff --git a/pkg/kernel/lib/ast.dart b/pkg/kernel/lib/ast.dart
index 9d6d5cdd073424bf9d2999e6e6673af3d96dd8bc..5845e4863ea778a28d1f0a041195ed5f21443d9c 100644
--- a/pkg/kernel/lib/ast.dart
+++ b/pkg/kernel/lib/ast.dart
@@ -2750,6 +2750,119 @@ class CheckLibraryIsLoaded extends Expression {
   transformChildren(Transformer v) {}
 }
 
+/// Expression of the form `MakeVector(N)` where `N` is an integer representing
+/// the length of the vector.
+///
+/// For detailed comment about Vectors see [VectorType].
+class VectorCreation extends Expression {
+  int length;
+
+  VectorCreation(this.length);
+
+  accept(ExpressionVisitor v) => v.visitVectorCreation(this);
+  accept1(ExpressionVisitor1 v, arg) => v.visitVectorCreation(this, arg);
+
+  visitChildren(Visitor v) {}
+
+  transformChildren(Transformer v) {}
+
+  DartType getStaticType(TypeEnvironment types) {
+    return const VectorType();
+  }
+}
+
+/// Expression of the form `v[i]` where `v` is a vector expression, and `i` is
+/// an integer index.
+class VectorGet extends Expression {
+  Expression vectorExpression;
+  int index;
+
+  VectorGet(this.vectorExpression, this.index) {
+    vectorExpression?.parent = this;
+  }
+
+  accept(ExpressionVisitor v) => v.visitVectorGet(this);
+  accept1(ExpressionVisitor1 v, arg) => v.visitVectorGet(this, arg);
+
+  visitChildren(Visitor v) {
+    vectorExpression.accept(v);
+  }
+
+  transformChildren(Transformer v) {
+    if (vectorExpression != null) {
+      vectorExpression = vectorExpression.accept(v);
+      vectorExpression?.parent = this;
+    }
+  }
+
+  DartType getStaticType(TypeEnvironment types) {
+    return const DynamicType();
+  }
+}
+
+/// Expression of the form `v[i] = x` where `v` is a vector expression, `i` is
+/// an integer index, and `x` is an arbitrary expression.
+class VectorSet extends Expression {
+  Expression vectorExpression;
+  int index;
+  Expression value;
+
+  VectorSet(this.vectorExpression, this.index, this.value) {
+    vectorExpression?.parent = this;
+    value?.parent = this;
+  }
+
+  accept(ExpressionVisitor v) => v.visitVectorSet(this);
+  accept1(ExpressionVisitor1 v, arg) => v.visitVectorSet(this, arg);
+
+  visitChildren(Visitor v) {
+    vectorExpression.accept(v);
+    value.accept(v);
+  }
+
+  transformChildren(Transformer v) {
+    if (vectorExpression != null) {
+      vectorExpression = vectorExpression.accept(v);
+      vectorExpression?.parent = this;
+    }
+    if (value != null) {
+      value = value.accept(v);
+      value?.parent = this;
+    }
+  }
+
+  DartType getStaticType(TypeEnvironment types) {
+    return value.getStaticType(types);
+  }
+}
+
+/// Expression of the form `CopyVector(v)` where `v` is a vector expression.
+class VectorCopy extends Expression {
+  Expression vectorExpression;
+
+  VectorCopy(this.vectorExpression) {
+    vectorExpression?.parent = this;
+  }
+
+  accept(ExpressionVisitor v) => v.visitVectorCopy(this);
+  accept1(ExpressionVisitor1 v, arg) => v.visitVectorCopy(this, arg);
+
+  visitChildren(Visitor v) {
+    vectorExpression.accept(v);
+  }
+
+  transformChildren(Transformer v) {
+    if (vectorExpression != null) {
+      vectorExpression = vectorExpression.accept(v);
+      vectorExpression?.parent = this;
+    }
+  }
+
+  DartType getStaticType(TypeEnvironment types) {
+    return const VectorType();
+  }
+}
+
 // ------------------------------------------------------------------------
 //                              STATEMENTS
 // ------------------------------------------------------------------------
@@ -3652,6 +3765,36 @@ class InterfaceType extends DartType {
   }
 }
 
+/// [VectorType] represents Vectors, a special kind of data that is not
+/// available for use by Dart programmers directly. It is used by Kernel
+/// transformations as efficient index-based storage.
+///
+/// * Vectors aren't user-visible. For example, they are not supposed to be
+/// exposed to Dart programs through variables or be visible in stack traces.
+///
+/// * Vectors have fixed length at runtime. The length is known at compile
+/// time, and [VectorCreation] AST node stores it in a field.
+///
+/// * Indexes for accessing and assigning Vector items are known at compile
+/// time. The corresponding [VectorGet] and [VectorSet] AST nodes store the
+/// index in a field.
+///
+/// * For efficiency considerations, bounds checks aren't performed for Vectors.
+/// If necessary, a transformer or verifier can do this checks at compile-time,
+/// after adding length field to [VectorType], to make sure that previous
+/// transformations didn't introduce any access errors.
+///
+/// * Access to Vectors is untyped.
+///
+/// * Vectors can be used by various transformations of Kernel programs.
+/// Currently they are used by Closure Conversion to represent closure contexts.
+class VectorType extends DartType {
+  const VectorType();
+
+  accept(DartTypeVisitor v) => v.visitVectorType(this);
+  visitChildren(Visitor v) {}
+}
+
 /// A possibly generic function type.
 class FunctionType extends DartType {
   final List<TypeParameter> typeParameters;