Fix handling of wasm import modules and names
The WebAssembly targets of rustc have weird issues around name mangling
and import the same name from different modules. This all largely stems
from the fact that we're using literal symbol names in LLVM IR to
represent what a function is called when it's imported, and we're not
using the wasm-specific `wasm-import-name` attribute. This in turn leads
to two issues:
* If, in the same codegen unit, the same FFI symbol is referenced twice
then rustc, when translating to LLVM IR, will only reference one
symbol from the first wasm module referenced.
* There's also a bug in LLD [1] where even if two codegen units
reference different modules, having the same symbol names means that
LLD coalesces the symbols and only refers to one wasm module.
Put another way, all our imported wasm symbols from the environment are
keyed off their LLVM IR symbol name, which has lots of collisions today.
This commit fixes the issue by implementing two changes:
1. All wasm symbols with `#[link(wasm_import_module = "...")]` are
mangled by default in LLVM IR. This means they're all given unique names.
2. Symbols then use the `wasm-import-name` attribute to ensure that the
WebAssembly file uses the correct import name.
When put together this should ensure we don't trip over the LLD bug [1]
and we also codegen IR correctly always referencing the right symbols
with the right import module/name pairs.
Closes#50021Closes#56309Closes#63562
[1]: https://bugs.llvm.org/show_bug.cgi?id=44316
Merge `TraitItem` & `ImplItem into `AssocItem`
In this PR we:
- Merge `{Trait,Impl}Item{Kind?}` into `AssocItem{Kind?}` as discussed in https://github.com/rust-lang/rust/issues/65041#issuecomment-538105286.
- This is done by using the cover grammar of both forms.
- In particular, it requires that we syntactically allow (under `#[cfg(FALSE)]`):
- `default`ness on `trait` items,
- `impl` items without a body / definition (`const`, `type`, and `fn`),
- and associated `type`s in `impl`s with bounds, e.g., `type Foo: Ord;`.
- The syntactic restrictions are replaced by semantic ones in `ast_validation`.
- Move syntactic restrictions around C-variadic parameters from the parser into `ast_validation`:
- `fn`s in all contexts now syntactically allow `...`,
- `...` can occur anywhere in the list syntactically (`fn foo(..., x: usize) {}`),
- and `...` can be the sole parameter (`fn foo(...) {}`.
r? @petrochenkov
Add a raw "address of" operator
* Parse and feature gate `&raw [const | mut] expr` (feature gate name is `raw_address_of`)
* Add `mir::Rvalue::AddressOf`
* Use the new `Rvalue` for:
* the new syntax
* reference to pointer casts
* drop shims for slices and arrays
* Stop using `mir::Rvalue::Cast` with a reference as the operand
* Correctly evaluate `mir::Rvalue::{Ref, AddressOf}` in constant propagation
cc @Centril @RalfJung @oli-obk @eddyb
cc #64490
Indicate origin of where type parameter for uninferred types
Based on #65951 (which is not merge yet), fixes#67277.
This PR improves a little the diagnostic for code like:
```
async fn foo() {
bar().await;
}
async fn bar<T>() -> () {}
```
by showing:
```
error[E0698]: type inside `async fn` body must be known in this context
--> unresolved_type_param.rs:9:5
|
9 | bar().await;
| ^^^ cannot infer type for type parameter `T` declared on the function `bar`
|
...
```
(The
```
declared on the function `bar`
```
part is new)
A small side note: `Vec` and `slice` seem to resist this change, because querying `item_name()` panics, and `get_opt_name()` returns `None`.
r? @estebank
Fix up Command Debug output when arg0 is specified.
PR https://github.com/rust-lang/rust/pull/66512 added the ability to set argv[0] on
Command. As a side effect, it changed the Debug output to print both the program and
argv[0], which in practice results in stuttery output (`"echo" "echo" "foo"`).
This PR reverts the behaviour to the the old one, so that the command is only printed
once - unless arg0 has been set. In that case it emits `"[command]" "arg0" "arg1" ...`.
Suggest associated type when the specified one cannot be found
Fixes#67386, so code like this:
```
use std::ops::Deref;
fn homura<T: Deref<Trget = i32>>(_: T) {}
fn main() {}
```
results in:
```
error[E0220]: associated type `Trget` not found for `std::ops::Deref`
--> type-binding.rs:6:20
|
6 | fn homura<T: Deref<Trget = i32>>(_: T) {}
| ^^^^^^^^^^^ help: there is an associated type with a similar name: `Target`
error: aborting due to previous error
```
(The `help` is new)
I used an `all_candidates: impl Fn() -> Iterator<...>` instead of `collect`ing to avoid the cost of allocating the Vec when no errors are found, at the expense of a little added complexity.
r? @estebank
`hir::BorrowKind::Raw` borrows and casting a reference to a raw
pointer no longer do a reborrow followed by a cast. Instead we
dereference and take the address.
This reverts commit 3ed3b8bb7b, reversing
changes made to 99b89533d4.
We will reland a similar patch at a future date but for now we should get a nightly
released in a few hours with the parallel patch, so this should be
reverted to make sure that the next nightly is not parallel-enabled.
This also removes the unused NO_PARALLEL_COMPILER flag; if we want that
functionality we can readd it but this makes sure we really are parallel
everywhere.
This also patches a test that has differing output in the parallel case
(hopefully deterministically so!).
PR https://github.com/rust-lang/rust/pull/66512 added the ability to set argv[0] on
Command. As a side effect, it changed the Debug output to print both the program and
argv[0], which in practice results in stuttery output ("echo echo foo").
This PR reverts the behaviour to the the old one, so that the command is only printed
once - unless arg0 has been set. In that case it emits "[command] arg0 arg1 ...".
The WebAssembly targets of rustc have weird issues around name mangling
and import the same name from different modules. This all largely stems
from the fact that we're using literal symbol names in LLVM IR to
represent what a function is called when it's imported, and we're not
using the wasm-specific `wasm-import-name` attribute. This in turn leads
to two issues:
* If, in the same codegen unit, the same FFI symbol is referenced twice
then rustc, when translating to LLVM IR, will only reference one
symbol from the first wasm module referenced.
* There's also a bug in LLD [1] where even if two codegen units
reference different modules, having the same symbol names means that
LLD coalesces the symbols and only refers to one wasm module.
Put another way, all our imported wasm symbols from the environment are
keyed off their LLVM IR symbol name, which has lots of collisions today.
This commit fixes the issue by implementing two changes:
1. All wasm symbols with `#[link(wasm_import_module = "...")]` are
mangled by default in LLVM IR. This means they're all given unique names.
2. Symbols then use the `wasm-import-name` attribute to ensure that the
WebAssembly file uses the correct import name.
When put together this should ensure we don't trip over the LLD bug [1]
and we also codegen IR correctly always referencing the right symbols
with the right import module/name pairs.
Closes#50021Closes#56309Closes#63562
[1]: https://bugs.llvm.org/show_bug.cgi?id=44316
Enable `loop` and `while` in constants behind a feature flag
This PR is an initial implementation of #52000. It adds a `const_loop` feature gate, which allows `while` and `loop` expressions through both HIR and MIR const-checkers if enabled. `for` expressions remain forbidden by the HIR const-checker, since they desugar to a call to `IntoIterator::into_iter`, which will be rejected anyways.
`while` loops also require [`#![feature(const_if_match)]`](https://github.com/rust-lang/rust/pull/66507), since they have a conditional built into them. The diagnostics from the HIR const checker will suggest this to the user.
r? @oli-obk
cc @rust-lang/wg-const-eval
Require stable/unstable annotations for the constness of all stable fns with a const modifier
r? @RalfJung @Centril
Every `#[stable]` const fn now needs either a `#[rustc_const_unstable]` attribute or a `#[rustc_const_stable]` attribute. You can't silently stabilize the constness of a function anymore.
Improve diagnostics and code for exhaustiveness of empty matches
There was a completely separate check and diagnostics for the case of an empty match. This led to slightly different error messages and duplicated code.
This improves code reuse and generally clarifies what happens for empty matches. This also clarifies the action of the `exhaustive_patterns` feature, and ensures that this feature doesn't change diagnostics in places it doesn't need to.
