Fix crash in dartc when given cyclic type variable bounds.

compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java

Index: compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
diff --git a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
index c9761333d2a33ed23b0db34c9bfc79ffed9ce477..b5762cd79361bf69eef54e2dd7e8c03b55452ca1 100644
--- a/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
+++ b/compiler/java/com/google/dart/compiler/type/TypeAnalyzer.java
@@ -604,6 +604,45 @@ public class TypeAnalyzer implements DartCompilationPhase {
       }
     }
 
+    /* Check for a type variable is repeated in its own bounds:
+     * e.g. Foo<T extends T>
+     */
+    private void checkCyclicBounds(List<? extends Type> arguments) {
+      for (Type argument : arguments) {
+        if (TypeKind.of(argument).equals(TypeKind.VARIABLE)) {
+          TypeVariable typeVar = (TypeVariable) argument;
+          checkCyclicBound(typeVar, typeVar.getTypeVariableElement().getBound());
+        }
+      }
+    }
+
+    private void checkCyclicBound(TypeVariable variable, Type bound) {
+      switch(TypeKind.of(bound)) {
+        case VARIABLE: {
+          TypeVariable boundType = (TypeVariable)bound;
+          if (boundType.equals(variable)) {
+            onError(boundType.getElement().getNode(),
+                    TypeErrorCode.CYCLIC_REFERENCE_TO_TYPE_VARIABLE,
+                    boundType.getElement().getOriginalSymbolName());
+          }
+          break;
+        }
+        case INTERFACE: {
+          InterfaceType iType = (InterfaceType)bound;
+          for (Type argument : iType.getArguments()) {
+            checkCyclicBound(variable, argument);
+          }
+          break;
+        }
+        case FUNCTION_ALIAS: {
+          FunctionAliasType fType = (FunctionAliasType)bound;
+          for (Type argument: fType.getArguments()) {
+            checkCyclicBound(variable, argument);
+          }
+        }
+      }
+    }
+
     Type typeOf(DartNode node) {
       if (node == null) {
         return dynamicType;
@@ -713,6 +752,7 @@ public class TypeAnalyzer implements DartCompilationPhase {
     public Type visitClass(DartClass node) {
       ClassElement element = node.getSymbol();
       InterfaceType type = element.getType();
+      checkCyclicBounds(type.getArguments());
       findUnimplementedMembers(element);
       setCurrentClass(type);
       visit(node.getTypeParameters());
@@ -883,7 +923,6 @@ public class TypeAnalyzer implements DartCompilationPhase {
           typeError(iterableExpression, TypeErrorCode.FOR_IN_WITH_ITERATOR_FIELD);
         }
       }
-
       return typeAsVoid(node);
     }
 
@@ -914,6 +953,10 @@ public class TypeAnalyzer implements DartCompilationPhase {
 
     @Override
     public Type visitFunctionTypeAlias(DartFunctionTypeAlias node) {
+      if (TypeKind.of(node.getSymbol().getType()).equals(TypeKind.FUNCTION_ALIAS)) {
+        FunctionAliasType type = node.getSymbol().getType();
+        checkCyclicBounds(type.getElement().getTypeParameters());
+      }
       return typeAsVoid(node);
     }