@Nullable public static PsiType getExpectedClosureReturnType(GrClosableBlock closure) { final Set<PsiType> expectedTypes = getDefaultExpectedTypes(closure); List<PsiType> expectedReturnTypes = new ArrayList<PsiType>(); for (PsiType expectedType : expectedTypes) { if (!(expectedType instanceof PsiClassType)) return null; final PsiClassType.ClassResolveResult resolveResult = ((PsiClassType) expectedType).resolveGenerics(); final PsiClass resolved = resolveResult.getElement(); if (resolved == null || !(GroovyCommonClassNames.GROOVY_LANG_CLOSURE.equals(resolved.getQualifiedName()))) return null; final PsiTypeParameter[] typeParameters = resolved.getTypeParameters(); if (typeParameters.length != 1) return null; final PsiTypeParameter expected = typeParameters[0]; final PsiType expectedReturnType = resolveResult.getSubstitutor().substitute(expected); if (expectedReturnType == PsiType.VOID || expectedReturnType == null) return null; expectedReturnTypes.add(expectedReturnType); } return TypesUtil.getLeastUpperBoundNullable(expectedReturnTypes, closure.getManager()); }