kernel->ssa: implement assert statements

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

Index: pkg/compiler/lib/src/ssa/builder_kernel.dart
diff --git a/pkg/compiler/lib/src/ssa/builder_kernel.dart b/pkg/compiler/lib/src/ssa/builder_kernel.dart
index a309e3911e9bcdfa4f59b3942ccca4d25a70a8b8..bb19a1edba9cee65422d8a149a43a117afa5b8f5 100644
--- a/pkg/compiler/lib/src/ssa/builder_kernel.dart
+++ b/pkg/compiler/lib/src/ssa/builder_kernel.dart
@@ -108,7 +108,11 @@ class KernelSsaBuilder extends ir.Visitor with GraphBuilder {
 
   void buildField(ir.Field field) {
     openFunction();
-    field.initializer.accept(this);
+    if (field.initializer != null) {
+      field.initializer.accept(this);
+    } else {
+      stack.add(graph.addConstantNull(compiler));
+    }
     HInstruction value = pop();
     closeAndGotoExit(new HReturn(value, null));
     closeFunction();
@@ -420,6 +424,36 @@ class KernelSsaBuilder extends ir.Visitor with GraphBuilder {
   }
 
   @override
+  void visitAssertStatement(ir.AssertStatement assertStatement) {
+    if (!compiler.options.enableUserAssertions) return;
+    if (assertStatement.message == null) {
+      assertStatement.condition.accept(this);
+      // TODO(het): should these be desugared in a kernel transformation?

[Siggi Cherem (dart-lang), 2016/09/29 15:36:52]

maybe - but I think it's possible that we could use assertions to improve static
analysis in the future, so it might be of interest to keep it around until
later.

[Harry Terkelsen, 2016/09/29 21:16:21]

Removed TODO after our team meeting discussing this

+      _pushStaticInvocation(astAdapter.assertHelper, <HInstruction>[pop()],
+          astAdapter.assertHelperReturnType);
+      pop();
+      return;
+    }
+
+    // if (assertTest(condition)) assertThrow(message);
+    void buildCondition() {
+      assertStatement.condition.accept(this);
+      _pushStaticInvocation(astAdapter.assertTest, <HInstruction>[pop()],
+          astAdapter.assertTestReturnType);
+    }
+
+    void fail() {
+      assertStatement.message.accept(this);
+      _pushStaticInvocation(astAdapter.assertThrow, <HInstruction>[pop()],
+          astAdapter.assertThrowReturnType);
+      pop();
+    }
+
+    SsaBranchBuilder brancher = new SsaBranchBuilder(this, compiler);
+    brancher.handleIf(buildCondition, fail, null);

[Siggi Cherem (dart-lang), 2016/09/29 15:36:52]

suggestion for later: it seems we always do:

  SsaBranchBuilder branch = new SsaBranchBuilder(this, compiler);
  branch.handleSomething(a, b, c);

It might be worth adding to GraphBuilder some helpers so we don't directly
allocate the BranchBuilder. We could keep the builder/handle divide like:

   addBranch().handleIf(a, b, c);

or we could further simplify it and stop exposing the branch builder if we can:

   addIf(a, b, c);


thoughts?

[Harry Terkelsen, 2016/09/29 21:16:21]

Good idea. I moved these to graph_builder

+  }
+
+  @override
   void visitConditionalExpression(ir.ConditionalExpression conditional) {
     SsaBranchBuilder brancher = new SsaBranchBuilder(this, compiler);
     brancher.handleConditional(