Preserve type annotations better after type rewriting. #1704
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Sometimes we rewrite types, for example to see that the return type of `T foo()` in `Bar<T>` is actually `String` in `class Baz implements Bar<String>`. Unfortunately rewriting types using the `javax.lang.model` API leads to the loss of any type annotations they originally had. If we had `@Nullable T foo()` it would become just `String foo()` rather than `@Nullable String foo()`. So we introduce a new class `AnnotatedTypeMirror` that tracks both the original type (with its annotations) and the rewritten type (without them), so we can combine the two when writing types into the generated code. This is not a fully general solution. We will indeed reconstruct `@Nullable String` in the example, but we will still lose the annotation when rewriting `List<@nullable T>` as `List<String>`. I think the only way around that is to forgo the use of [`Types.asMemberOf`](https://docs.oracle.com/en/java/javase/21/docs/api/java.compiler/javax/lang/model/util/Types.html#asMemberOf(javax.lang.model.type.DeclaredType,javax.lang.model.element.Element)) and instead substitute type variables ourselves. That's similar to but more general than what we already do in [`TypeVariables.substituteTypeVariables`](https://github.com/google/auto/blob/e20db259ac2d6b176e396639a7540cadec38a9aa/value/src/main/java/com/google/auto/value/processor/TypeVariables.java#L169). It is made more awkward by the lack of a way to synthesize a `TypeMirror` with annotations; see https://bugs.openjdk.org/browse/JDK-8174126. (We could implement `TypeMirror` and its subinterfaces ourselves, but the resulting objects would not work with the `javax.lang.model` API.) RELNOTES=Handling of type annotations on inherited methods has been improved. PiperOrigin-RevId: 605781385
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…setters. This handles a further case using the logic introduced by #1704. RELNOTES=Type-use annotations such as `@Nullable` are now better preserved in generated builder setter method parameters. Previously they could be lost in some circumstances, for example with `@Nullable T`. PiperOrigin-RevId: 699721928
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…setters. This handles a further case using the logic introduced by #1704. RELNOTES=Type-use annotations such as `@Nullable` are now better preserved in generated builder setter method parameters. Previously they could be lost in some circumstances, for example with `@Nullable T`. PiperOrigin-RevId: 699982315
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Preserve type annotations better after type rewriting.
Sometimes we rewrite types, for example to see that the return type of
T foo()inBar<T>is actuallyStringinclass Baz implements Bar<String>. Unfortunately rewriting types using thejavax.lang.modelAPI leads to the loss of any type annotations they originally had. If we had@Nullable T foo()it would become justString foo()rather than@Nullable String foo(). So we introduce a new classAnnotatedTypeMirrorthat tracks both the original type (with its annotations) and the rewritten type (without them), so we can combine the two when writing types into the generated code.This is not a fully general solution. We will indeed reconstruct
@Nullable Stringin the example, but we will still lose the annotation when rewritingList<@Nullable T>asList<String>. I think the only way around that is to forgo the use ofTypes.asMemberOfand instead substitute type variables ourselves. That's similar to but more general than what we already do inTypeVariables.substituteTypeVariables. It is made more awkward by the lack of a way to synthesize aTypeMirrorwith annotations; see https://bugs.openjdk.org/browse/JDK-8174126. (We could implementTypeMirrorand its subinterfaces ourselves, but the resulting objects would not work with thejavax.lang.modelAPI.)RELNOTES=Handling of type annotations on inherited methods has been improved.