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37ed7a4438
This is a very large commit since a lot needs to be changed in order to make the tests pass. The salient changes are: - `ConstArgKind` gets a new `Path` variant, and all const params are now represented using it. Non-param paths still use `ConstArgKind::Anon` to prevent this change from getting too large, but they will soon use the `Path` variant too. - `ConstArg` gets a distinct `hir_id` field and its own variant in `hir::Node`. This affected many parts of the compiler that expected the parent of an `AnonConst` to be the containing context (e.g., an array repeat expression). They have been changed to check the "grandparent" where necessary. - Some `ast::AnonConst`s now have their `DefId`s created in rustc_ast_lowering rather than `DefCollector`. This is because in some cases they will end up becoming a `ConstArgKind::Path` instead, which has no `DefId`. We have to solve this in a hacky way where we guess whether the `AnonConst` could end up as a path const since we can't know for sure until after name resolution (`N` could refer to a free const or a nullary struct). If it has no chance as being a const param, then we create a `DefId` in `DefCollector` -- otherwise we decide during ast_lowering. This will have to be updated once all path consts use `ConstArgKind::Path`. - We explicitly use `ConstArgHasType` for array lengths, rather than implicitly relying on anon const type feeding -- this is due to the addition of `ConstArgKind::Path`. - Some tests have their outputs changed, but the changes are for the most part minor (including removing duplicate or almost-duplicate errors). One test now ICEs, but it is for an incomplete, unstable feature and is now tracked at #127009.
27 lines
1.3 KiB
Rust
27 lines
1.3 KiB
Rust
// Given a const argument `a`: `{ N }` and some const argument `b` which references the
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// first anon const like so: `{ [1; a] }`. The `b` anon const should not be allowed to use
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// any generic parameters as:
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// - The anon const is not a simple bare parameter, e.g. `N`
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// - The anon const is not the *length* of an array repeat expression, e.g. the `N` in `[1; N]`.
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//
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// On the other hand `a` *is* a const argument for the length of a repeat expression and
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// so it *should* inherit the generics declared on its parent definition. (This hack is
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// introduced for backwards compatibility and is tracked in #76200)
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//
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// In this specific case `a`'s parent should be `b` which does not have any generics.
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// This means that even though `a` inherits generics from `b`, it still winds up not having
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// access to any generic parameters. If `a` were to inherit its generics from the surrounding
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// function `foo` then the reference to `a` from `b` would contain generic parameters not usable
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// by `b` which would cause us to ICE.
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fn bar<const N: usize>() {}
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fn foo<const N: usize>() {
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bar::<{ [1; N] }>();
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//~^ ERROR: generic parameters may not be used in const operations
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bar::<{ [1; { N + 1 }] }>();
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//~^ ERROR: generic parameters may not be used in const operations
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}
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fn main() {}
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