public static String checkReturnType(
PsiMethodReferenceExpression expression,
JavaResolveResult result,
PsiType functionalInterfaceType) {
final PsiElement resolve = result.getElement();
if (resolve instanceof PsiMethod) {
final PsiClass containingClass = ((PsiMethod) resolve).getContainingClass();
LOG.assertTrue(containingClass != null);
PsiSubstitutor subst = result.getSubstitutor();
PsiClass qContainingClass = getQualifierResolveResult(expression).getContainingClass();
if (qContainingClass != null
&& isReceiverType(functionalInterfaceType, containingClass, (PsiMethod) resolve)) {
subst = TypeConversionUtil.getClassSubstitutor(containingClass, qContainingClass, subst);
LOG.assertTrue(subst != null);
}
final PsiType interfaceReturnType =
LambdaUtil.getFunctionalInterfaceReturnType(functionalInterfaceType);
PsiType returnType =
PsiTypesUtil.patchMethodGetClassReturnType(
expression,
expression,
(PsiMethod) resolve,
null,
PsiUtil.getLanguageLevel(expression));
if (returnType == null) {
returnType = ((PsiMethod) resolve).getReturnType();
}
PsiType methodReturnType = subst.substitute(returnType);
if (interfaceReturnType != null && interfaceReturnType != PsiType.VOID) {
if (methodReturnType == null) {
methodReturnType =
JavaPsiFacade.getElementFactory(expression.getProject())
.createType(containingClass, subst);
}
if (!TypeConversionUtil.isAssignable(interfaceReturnType, methodReturnType, false)) {
return "Bad return type in method reference: cannot convert "
+ methodReturnType.getCanonicalText()
+ " to "
+ interfaceReturnType.getCanonicalText();
}
}
}
return null;
}
@Nullable
private static PsiType getResultType(
PsiMethodCallExpression call,
PsiReferenceExpression methodExpression,
JavaResolveResult result,
@NotNull final LanguageLevel languageLevel) {
final PsiMethod method = (PsiMethod) result.getElement();
if (method == null) return null;
boolean is15OrHigher = languageLevel.compareTo(LanguageLevel.JDK_1_5) >= 0;
final PsiType getClassReturnType =
PsiTypesUtil.patchMethodGetClassReturnType(
call,
methodExpression,
method,
new Condition<IElementType>() {
@Override
public boolean value(IElementType type) {
return type != JavaElementType.CLASS;
}
},
languageLevel);
if (getClassReturnType != null) {
return getClassReturnType;
}
PsiType ret = method.getReturnType();
if (ret == null) return null;
if (ret instanceof PsiClassType) {
ret = ((PsiClassType) ret).setLanguageLevel(languageLevel);
}
if (is15OrHigher) {
return captureReturnType(call, method, ret, result, languageLevel);
}
return TypeConversionUtil.erasure(ret);
}
