Integrity checker for CPS and Tree IR.

pkg/compiler/lib/src/dart_backend/backend.dart

Index: pkg/compiler/lib/src/dart_backend/backend.dart
diff --git a/pkg/compiler/lib/src/dart_backend/backend.dart b/pkg/compiler/lib/src/dart_backend/backend.dart
index 90baf1b2d30221dea10da42994cd2f62098c638f..6fd3c1cfced4c1dc746628e6183ae73583c7b1b4 100644
--- a/pkg/compiler/lib/src/dart_backend/backend.dart
+++ b/pkg/compiler/lib/src/dart_backend/backend.dart
@@ -131,26 +131,41 @@ class DartBackend extends Backend {
 
   void codegen(CodegenWorkItem work) { }
 
+  static bool checkTreeIntegrity(tree_ir.ExecutableDefinition node) {
+    new CheckTreeIntegrity().check(node);
+    return true; // So this can be used from assert().
+  }
+
+  static bool checkCpsIntegrity(cps_ir.ExecutableDefinition node) {
+    new CheckCpsIntegrity().check(node);
+    return true; // So this can be used from assert().
+  }
+
   /// Create an [ElementAst] from the CPS IR.
   static ElementAst createElementAst(
        ElementAstCreationContext context,
        Element element,
        cps_ir.ExecutableDefinition cpsDefinition) {
-    // Transformations on the CPS IR.
     context.traceCompilation(element.name);
+    context.traceGraph('CPS builder', cpsDefinition);
+    assert(checkCpsIntegrity(cpsDefinition));
+
+    // Transformations on the CPS IR.
+    void applyCpsPass(String name, cps_opt.Pass pass) {
+      pass.rewrite(cpsDefinition);
+      context.traceGraph(name, cpsDefinition);
+      assert(checkCpsIntegrity(cpsDefinition));
+    }
 
     // TODO(karlklose): enable type propagation for dart2dart when constant
     // types are correctly marked as instantiated (Issue 21880).
-    new TypePropagator(context.dartTypes,
-                       context.constantSystem,
-                       new UnitTypeSystem(),
-                       context.internalError)
-        .rewrite(cpsDefinition);
-    context.traceGraph("Sparse constant propagation", cpsDefinition);
-    new RedundantPhiEliminator().rewrite(cpsDefinition);
-    context.traceGraph("Redundant phi elimination", cpsDefinition);
-    new ShrinkingReducer().rewrite(cpsDefinition);
-    context.traceGraph("Shrinking reductions", cpsDefinition);
+    applyCpsPass('Sparse constant propagation',
+        new TypePropagator(context.dartTypes,
+                           context.constantSystem,
+                           new UnitTypeSystem(),
+                           context.internalError));
+    applyCpsPass('Redundant phi elimination', new RedundantPhiEliminator());
+    applyCpsPass('Shrinking reductions', new ShrinkingReducer());
 
     // Do not rewrite the IR after variable allocation.  Allocation
     // makes decisions based on an approximation of IR variable live
@@ -162,16 +177,21 @@ class DartBackend extends Backend {
     tree_ir.ExecutableDefinition treeDefinition = builder.build(cpsDefinition);
     assert(treeDefinition != null);
     context.traceGraph('Tree builder', treeDefinition);
+    assert(checkTreeIntegrity(treeDefinition));
 
     // Transformations on the Tree IR.
-    new StatementRewriter().rewrite(treeDefinition);
-    context.traceGraph('Statement rewriter', treeDefinition);
-    new CopyPropagator().rewrite(treeDefinition);
-    context.traceGraph('Copy propagation', treeDefinition);
-    new LoopRewriter().rewrite(treeDefinition);
-    context.traceGraph('Loop rewriter', treeDefinition);
-    new LogicalRewriter().rewrite(treeDefinition);
-    context.traceGraph('Logical rewriter', treeDefinition);
+    void applyTreePass(String name, tree_opt.Pass pass) {
+      pass.rewrite(treeDefinition);
+      context.traceGraph(name, treeDefinition);
+      assert(checkTreeIntegrity(treeDefinition));
+    }
+
+    applyTreePass('Statement rewriter', new StatementRewriter());
+    applyTreePass('Copy propagation', new CopyPropagator());
+    applyTreePass('Loop rewriter', new LoopRewriter());
+    applyTreePass('Logical rewriter', new LogicalRewriter());
+
+    // Backend-specific transformations.
     new backend_ast_emitter.UnshadowParameters().unshadow(treeDefinition);
     context.traceGraph('Unshadow parameters', treeDefinition);