Compute source spans for IR nodes and J/K-elements

pkg/compiler/lib/src/types/type_mask.dart

Index: pkg/compiler/lib/src/types/type_mask.dart
diff --git a/pkg/compiler/lib/src/types/type_mask.dart b/pkg/compiler/lib/src/types/type_mask.dart
index c855f89c12d1f0ec836b94d8076475fccafab93f..dd8a7b0d229ef703bfe41c6b1e19da761dc37d41 100644
--- a/pkg/compiler/lib/src/types/type_mask.dart
+++ b/pkg/compiler/lib/src/types/type_mask.dart
@@ -88,7 +88,7 @@ abstract class TypeMask implements ReceiverConstraint, AbstractValue {
     assert(
         closedWorld.isInstantiated(base),
         failedAt(
-            base,
+            base ?? CURRENT_ELEMENT_SPANNABLE,
             "Cannot create exact type mask for uninstantiated "
             "class $base.\n${closedWorld.dump(base)}"));
     return new FlatTypeMask.exact(base);
@@ -103,7 +103,7 @@ abstract class TypeMask implements ReceiverConstraint, AbstractValue {
     assert(
         closedWorld.isInstantiated(base),
         failedAt(
-            base,
+            base ?? CURRENT_ELEMENT_SPANNABLE,
             "Cannot create subclass type mask for uninstantiated "
             "class $base.\n${closedWorld.dump(base)}"));
     ClassEntity topmost = closedWorld.getLubOfInstantiatedSubclasses(base);
@@ -137,7 +137,7 @@ abstract class TypeMask implements ReceiverConstraint, AbstractValue {
     assert(
         closedWorld.isInstantiated(base),
         failedAt(
-            base,
+            base ?? CURRENT_ELEMENT_SPANNABLE,
             "Cannot create exact type mask for uninstantiated "
             "class $base.\n${closedWorld.dump(base)}"));
     return new FlatTypeMask.nonNullExact(base);
@@ -155,7 +155,7 @@ abstract class TypeMask implements ReceiverConstraint, AbstractValue {
     assert(
         closedWorld.isInstantiated(base),
         failedAt(
-            base,
+            base ?? CURRENT_ELEMENT_SPANNABLE,
             "Cannot create subclass type mask for uninstantiated "
             "class $base.\n${closedWorld.dump(base)}"));
     ClassEntity topmost = closedWorld.getLubOfInstantiatedSubclasses(base);