Handle forwarding constructors to unnamed mixin applications

pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart

Index: pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
diff --git a/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart b/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
index 6cce8985ee24d1d55bed4ca1bcf33163ea45898c..ff5df10a44f0ce5b8e167d66305bb132aa071a33 100644
--- a/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
+++ b/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
@@ -233,15 +233,37 @@ class KernelSorter implements Sorter {
 
   @override
   Iterable<ClassEntity> sortClasses(Iterable<ClassEntity> classes) {
-    return classes.toList()
-      ..sort((ClassEntity cls1, ClassEntity cls2) {
-        int r = _compareLibraries(cls1.library, cls2.library);
-        if (r != 0) return r;
-        ClassDefinition definition1 = elementMap.getClassDefinition(cls1);
-        ClassDefinition definition2 = elementMap.getClassDefinition(cls2);
-        return _compareSourceSpans(
-            cls1, definition1.location, cls2, definition2.location);
-      });
+    int compareClasses(ClassEntity cls1, ClassEntity cls2) {
+      int r = _compareLibraries(cls1.library, cls2.library);
+      if (r != 0) return r;
+      ClassDefinition definition1 = elementMap.getClassDefinition(cls1);
+      ClassDefinition definition2 = elementMap.getClassDefinition(cls2);
+      return _compareSourceSpans(
+          cls1, definition1.location, cls2, definition2.location);
+    }
+
+    List<ClassEntity> regularClasses = <ClassEntity>[];
+    List<ClassEntity> unnamedMixins = <ClassEntity>[];
+    for (ClassEntity cls in classes) {
+      if (elementMap.elementEnvironment.isUnnamedMixinApplication(cls)) {
+        unnamedMixins.add(cls);
+      } else {
+        regularClasses.add(cls);
+      }
+    }
+    List<ClassEntity> sorted = <ClassEntity>[];
+    regularClasses.sort(compareClasses);
+    sorted.addAll(regularClasses);
+    unnamedMixins.sort((a, b) {
+      int result = _compareLibraries(a.library, b.library);
+      if (result != 0) return result;
+      result = a.name.compareTo(b.name);
+      assert(result != 0,
+          failedAt(a, "Multiple mixins named ${a.name}: $a vs $b."));

[Siggi Cherem (dart-lang), 2017/09/01 15:41:49]

do we ensure today that if you do A extends Object with B and C extends Object
with B in the same file, then there is only one Object&B?

[Johnni Winther, 2017/09/01 16:13:48]

We do in the optimized mixin algorithm (ported from fasta), otherwise not.

+      return result;
+    });
+    sorted.addAll(unnamedMixins);
+    return sorted;
   }
 
   @override