support for Groovy 2.2's DelegatesTo#genericIndexType

plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/GrAnnotationUtil.java

@@ -34,4 +34,14 @@ public class GrAnnotationUtil {
     }
     return null;
   }
+
+  @Nullable
+  public static Integer inferIntegerAttribute(@NotNull PsiAnnotation annotation, @NotNull String attributeName) {
+    final PsiAnnotationMemberValue targetValue = annotation.findAttributeValue(attributeName);
+    if (targetValue instanceof PsiLiteral) {
+      final Object value = ((PsiLiteral)targetValue).getValue();
+      if (value instanceof Integer) return (Integer)value;
+    }
+    return null;
+  }
 }

plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/blocks/GrDelegatesToUtil.java

@@ -56,7 +56,7 @@ public class GrDelegatesToUtil {
     if (signature == null) return null;
 
     final GrClosureSignatureUtil.ArgInfo<PsiElement>[] map = GrClosureSignatureUtil.mapParametersToArguments(
-      signature, call.getNamedArguments(), call.getExpressionArguments(), call.getClosureArguments(), place, false, true
+      signature, call.getNamedArguments(), call.getExpressionArguments(), call.getClosureArguments(), place, false, false
     );
 
     if (map == null) {
@@ -112,7 +112,18 @@ public class GrDelegatesToUtil {
 
       final int parameter = findTargetParameter(delegatesTo, target);
       if (parameter >= 0) {
-        return map[parameter].type;
+        final PsiType type = map[parameter].type;
+        final Integer index = GrAnnotationUtil.inferIntegerAttribute(delegatesTo, "genericTypeIndex");
+        if (index == null) {
+          return type;
+        }
+        if (type instanceof PsiClassType) {
+          final PsiType[] parameters = ((PsiClassType)type).getParameters();
+          if (parameters.length > index) {
+            return parameters[index];
+          }
+        }
+        return null;
       }
     }
     else if (value instanceof PsiExpression) {

plugins/groovy/test/org/jetbrains/plugins/groovy/lang/resolve/ResolveWithDelegatesToTest.groovy

@@ -631,6 +631,15 @@ foo(4) {
 ''', 'Integer')
   }
 
+  void testGenericTypeIndex() {
+    assertScript('''\
+def foo(@DelegatesTo.Target def map, @DelegatesTo(genericTypeIndex = 1) Closure c) {}
+
+foo([1:'ab', 2:'cde']) {
+  sub<caret>string(1)
+}
+''', 'String')
+  }
 
   void assertScript(String text, String resolvedClass) {
     myFixture.configureByText('_a.groovy', text)