Jubilee 8c9e3749a1
Rollup merge of #136985 - zachs18:backend-repr-remove-uninhabited, r=workingjubilee
Do not ignore uninhabited types for function-call ABI purposes. (Remove BackendRepr::Uninhabited)

Accepted MCP: https://github.com/rust-lang/compiler-team/issues/832

Fixes #135802

Do not consider the inhabitedness of a type for function call ABI purposes.

* Remove the [`rustc_abi::BackendRepr::Uninhabited`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_abi/enum.BackendRepr.html) variant
  * Instead calculate the `BackendRepr` of uninhabited types "normally" (as though they were not uninhabited "at the top level", but still considering inhabitedness of variants to determine enum layout, etc)
* Add an `uninhabited: bool` field to [`rustc_abi::LayoutData`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_abi/struct.LayoutData.html) so inhabitedness of a `LayoutData` can still be queried when necessary (e.g. when determining if an enum variant needs a tag value allocated to it).

This should not affect type layouts (size/align/field offset); this should only affect function call ABI, and only of uninhabited types.

cc ``@RalfJung``
2025-02-20 14:58:18 -08:00
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UI Tests

This folder contains rustc's UI tests.

Test Directives (Headers)

Typically, a UI test will have some test directives / headers which are special comments that tell compiletest how to build and interpret a test.

As part of an ongoing effort to rewrite compiletest (see https://github.com/rust-lang/compiler-team/issues/536), a major change proposal to change legacy compiletest-style headers // <directive> to ui_test-style headers //@ <directive> was accepted (see https://github.com/rust-lang/compiler-team/issues/512.

An example directive is ignore-test. In legacy compiletest style, the header would be written as

// ignore-test

but in ui_test style, the header would be written as

//@ ignore-test

compiletest is changed to accept only //@ directives for UI tests (currently), and will reject and report an error if it encounters any comments // <content> that may be parsed as a legacy compiletest-style test header. To fix this, you should migrate to the ui_test-style header //@ <content>.