Use failedAt in more places

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

Index: pkg/compiler/lib/src/ssa/kernel_impact.dart
diff --git a/pkg/compiler/lib/src/ssa/kernel_impact.dart b/pkg/compiler/lib/src/ssa/kernel_impact.dart
index 9eba59eca88af3ac8c946092dd998f4e9ad31108..a4e2a3018ae137291e33272e0911871d8f604587 100644
--- a/pkg/compiler/lib/src/ssa/kernel_impact.dart
+++ b/pkg/compiler/lib/src/ssa/kernel_impact.dart
@@ -154,7 +154,7 @@ class KernelImpactBuilder extends ir.Visitor {
         impactBuilder.registerFeature(Feature.ASYNC_STAR);
         break;
       case ir.AsyncMarker.SyncYielding:
-        throw new SpannableAssertionFailure(CURRENT_ELEMENT_SPANNABLE,
+        failedAt(CURRENT_ELEMENT_SPANNABLE,
             "Unexpected async marker: ${asyncMarker}");
     }
   }
@@ -299,7 +299,7 @@ class KernelImpactBuilder extends ir.Visitor {
       ConstantValue value =
           elementAdapter.getConstantValue(node.arguments.positional.first);
       if (!value.isString) {
-        throw new SpannableAssertionFailure(
+        failedAt(
             CURRENT_ELEMENT_SPANNABLE,
             "Unexpected constant value in const Symbol(...) call: "
             "${value.toStructuredText()}");