implement kernel -> ssa for literals

pkg/compiler/lib/src/ssa/kernel_ast_adapter.dart

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:kernel/ast.dart' as ir;
+
+import '../constants/values.dart';
+import '../diagnostics/invariant.dart';
+import '../elements/elements.dart';
+import '../js_backend/js_backend.dart';
+import '../tree/tree.dart' as ast;
+
+/// A helper class that abstracts all accesses of the AST from Kernel nodes.
+///
+/// The goal is to remove all need for the AST from the Kernel SSA builder.
+class KernelAstAdapter {
+  final JavaScriptBackend backend;
+  final ResolvedAst resolvedAst;
+  final Map<ir.Node, ast.Node> nodeToAst;
+
+  KernelAstAdapter(this.backend, this.resolvedAst, this.nodeToAst);
+
+  ConstantValue getConstantFor(ir.Node node) {

[Siggi Cherem (dart-lang), 2016/08/26 20:27:11]

it seems to me like you only use this for Symbol, maybe we should restrict it to
just that?

+    ast.Node astNode = nodeToAst[node];
+    ConstantValue constantValue = backend.constants
+        .getConstantValueForNode(astNode, resolvedAst.elements);
+    assert(invariant(astNode, constantValue != null,
+        message: 'No constant computed for $node'));
+    return constantValue;
+  }
+}