Re: [weld-dev] Odd type assignability test
----- Original Message -----
From: "Laird Nelson" <ljnelson(a)gmail.com>
To: "weld-dev" <weld-dev(a)lists.jboss.org>
Sent: Monday, April 27, 2020 5:51:54 PM
Subject: Re: [weld-dev] Odd type assignability test
On Mon, Apr 27, 2020 at 5:38 AM Martin Kouba < mkouba(a)redhat.com > wrote:
I think that you're right. Foo<E> is basically Foo<E extends Object> and
according to the rules String is assignable to Object.
Just to be clear, this test (that I added temporarily to CovariantTypesTest
and ran just to make sure) fails (as I'd expect):
@Test
public <E> void testFooStringAssignableFromFooE() {
Type a = new TypeLiteral<Foo<String>>() {
}.getType();
Type b = new TypeLiteral<Foo<E>>() {
}.getType();
assertTrue(CovariantTypes.isAssignableFrom(a, b)); // kaboom
}
But this test (the one under discussion) in BeanTypeAssignabilityRules
succeeds (obviously or Weld's test suite would be broken):
@Test
public <E> void testStringFooMatchesVariableFoo() throws Exception {
Type stringFooType = new TypeLiteral<Foo<String>>() {
}.getType();
Type variableFooType = new TypeLiteral<Foo<E>>() {
}.getType();
Assert.assertTrue("Foo<String> should match Foo<E>",
getRules().matches(stringFooType, variableFooType));
}
So the rules CDI uses to do type matching (represented by
BeanTypeAssignabilityRules ) are deliberately different from those used by
JLS (represented by CovariantTypes ), right?
CovariantTypes/InvariantTypes are used by BeanTypeAssignabilityRules.
My understanding was that CDI dictates some rules, few of which are different or requiring
some extra steps compared to pure JLS. That's why during evaluation you go through
BeanTypeAssignabilityRules and whenever applicable you delegate to
Covariant/InvariantTypes.
Best,
Laird
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