Rewrite mixin application handling in Fasta.

pkg/front_end/lib/src/fasta/source/source_loader.dart

Index: pkg/front_end/lib/src/fasta/source/source_loader.dart
diff --git a/pkg/front_end/lib/src/fasta/source/source_loader.dart b/pkg/front_end/lib/src/fasta/source/source_loader.dart
index 806c279da5e7fde497988b88c523deb60c360465..99adbac79ad72f3144fe53984c1d178b5a3cbcdb 100644
--- a/pkg/front_end/lib/src/fasta/source/source_loader.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_loader.dart
@@ -23,7 +23,13 @@ import 'package:kernel/class_hierarchy.dart' show ClassHierarchy;
 import 'package:kernel/core_types.dart' show CoreTypes;
 
 import '../builder/builder.dart'
-    show Builder, ClassBuilder, EnumBuilder, LibraryBuilder;
+    show
+        Builder,
+        ClassBuilder,
+        EnumBuilder,
+        LibraryBuilder,
+        NamedTypeBuilder,
+        TypeBuilder;
 
 import '../compiler_context.dart' show CompilerContext;
 
@@ -336,10 +342,12 @@ class SourceLoader<L> extends Loader<L> {
             reported.add(cls);
           }
         }
+        String involvedString =
+            involved.map((c) => c.fullNameForErrors).join("', '");
         cls.addCompileTimeError(
             cls.charOffset,
-            "'${cls.name}' is a supertype of "
-            "itself via '${involved.map((c) => c.name).join(' ')}'.");
+            "'${cls.fullNameForErrors}' is a supertype of itself via "
+            "'$involvedString'.");
       }
     });
     ticker.logMs("Found cycles");
@@ -351,6 +359,7 @@ class SourceLoader<L> extends Loader<L> {
       coreLibrary["String"],
     ]);
     for (ClassBuilder cls in allClasses) {
+      if (cls.library.loader != this) continue;
       Set<ClassBuilder> directSupertypes = new Set<ClassBuilder>();
       target.addDirectSupertype(cls, directSupertypes);
       for (ClassBuilder supertype in directSupertypes) {
@@ -367,6 +376,32 @@ class SourceLoader<L> extends Loader<L> {
               "implemented.");
         }
       }
+      TypeBuilder mixedInType = cls.mixedInType;
+      if (mixedInType != null) {
+        bool isClassBuilder = false;
+        if (mixedInType is NamedTypeBuilder) {
+          var builder = mixedInType.builder;
+          if (builder is ClassBuilder) {
+            isClassBuilder = true;
+            for (Builder constructory in builder.constructors.local.values) {
+              if (constructory.isConstructor && !constructory.isSynthetic) {
+                cls.addCompileTimeError(
+                    cls.charOffset,
+                    "Can't use '${builder.fullNameForErrors}' as a mixin "
+                    "because it has constructors.");
+                builder.addCompileTimeError(
+                    constructory.charOffset,
+                    "This constructor prevents using "
+                    "'${builder.fullNameForErrors}' as a mixin.");
+              }
+            }
+          }
+        }
+        if (!isClassBuilder) {
+          cls.addCompileTimeError(cls.charOffset,
+              "The type '${mixedInType.fullNameForErrors}' can't be mixed in.");
+        }
+      }
     }
     ticker.logMs("Checked restricted supertypes");
   }