Remove gensym in format_args
This also fixes some things to allow us to export opaque macros from libcore:
* Don't consider items that are only reachable through opaque macros as public/exported (so they aren't linted as needing docs)
* Mark private items reachable from the root of libcore as unstable - they are now reachable (in principle) in other crates via macros in libcore
r? @petrochenkov
Move special treatment of `derive(Copy, PartialEq, Eq)` from expansion infrastructure to elsewhere
As described in https://github.com/rust-lang/rust/pull/62086#issuecomment-515195477.
Reminder:
- `derive(PartialEq, Eq)` makes the type it applied to a "structural match" type, so constants of this type can be used in patterns (and const generics in the future).
- `derive(Copy)` notifies other derives that the type it applied to implements `Copy`, so `derive(Clone)` can generate optimized code and other derives can generate code working with `packed` types and types with `rustc_layout_scalar_valid_range` attributes.
First, the special behavior is now enabled after properly resolving the derives, rather than after textually comparing them with `"Copy"`, `"PartialEq"` and `"Eq"` in `fn add_derived_markers`.
The markers are no longer kept as attributes in AST since derives cannot modify items and previously did it through hacks in the expansion infra.
Instead, the markers are now kept in a "global context" available from all the necessary places, namely - resolver.
For `derive(PartialEq, Eq)` the markers are created by the derive macros themselves and then consumed during HIR lowering to add the `#[structural_match]` attribute in HIR.
This is still a hack, but now it's a hack local to two specific macros rather than affecting the whole expansion infra.
Ideally we should find the way to put `#[structural_match]` on the impls rather than on the original item, and then consume it in `rustc_mir`, then no hacks in expansion and lowering will be required.
(I'll make an issue about this for someone else to solve, after this PR lands.)
The marker for `derive(Copy)` cannot be emitted by the `Copy` macro itself because we need to know it *before* the `Copy` macro is expanded for expanding other macros.
So we have to do it in resolve and block expansion of any derives in a `derive(...)` container until we know for sure whether this container has `Copy` in it or not.
Nasty stuff.
r? @eddyb or @matthewjasper
Rename `ItemKind::Ty` to `ItemKind::TyAlias`
The current name is not entirely clear without context and `TyAlias` is consistent with `ItemKind::TraitAlias`.
On `format!()` arg count mismatch provide extra info
When positional width and precision formatting flags are present in a
formatting string that has an argument count mismatch, provide extra
information pointing at them making it easiser to understand where the
problem may lay:
```
error: 4 positional arguments in format string, but there are 3 arguments
--> $DIR/ifmt-bad-arg.rs:78:15
|
LL | println!("{} {:.*} {}", 1, 3.2, 4);
| ^^ ^^--^ ^^ --- this parameter corresponds to the precision flag
| |
| this precision flag adds an extra required argument at position 1, which is why there are 4 arguments expected
|
= note: positional arguments are zero-based
= note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
error: 4 positional arguments in format string, but there are 3 arguments
--> $DIR/ifmt-bad-arg.rs:81:15
|
LL | println!("{} {:07$.*} {}", 1, 3.2, 4);
| ^^ ^^-----^ ^^ --- this parameter corresponds to the precision flag
| | |
| | this precision flag adds an extra required argument at position 1, which is why there are 4 arguments expected
| this width flag expects an `usize` argument at position 7, but there are 3 arguments
|
= note: positional arguments are zero-based
= note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
error: invalid reference to positional argument 7 (there are 3 arguments)
--> $DIR/ifmt-bad-arg.rs:84:18
|
LL | println!("{} {:07$} {}", 1, 3.2, 4);
| ^^^--^
| |
| this width flag expects an `usize` argument at position 7, but there are 3 arguments
|
= note: positional arguments are zero-based
= note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
```
Fix#49384.
When positional width and precision formatting flags are present in a
formatting string that has an argument count mismatch, provide extra
information pointing at them making it easiser to understand where the
problem may lay:
```
error: 4 positional arguments in format string, but there are 3 arguments
--> $DIR/ifmt-bad-arg.rs:78:15
|
LL | println!("{} {:.*} {}", 1, 3.2, 4);
| ^^ ^^--^ ^^ --- this parameter corresponds to the precision flag
| |
| this precision flag adds an extra required argument at position 1, which is why there are 4 arguments expected
|
= note: positional arguments are zero-based
= note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
error: 4 positional arguments in format string, but there are 3 arguments
--> $DIR/ifmt-bad-arg.rs:81:15
|
LL | println!("{} {:07$.*} {}", 1, 3.2, 4);
| ^^ ^^-----^ ^^ --- this parameter corresponds to the precision flag
| | |
| | this precision flag adds an extra required argument at position 1, which is why there are 4 arguments expected
| this width flag expects an `usize` argument at position 7, but there are 3 arguments
|
= note: positional arguments are zero-based
= note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
error: 3 positional arguments in format string, but there are 3 arguments
--> $DIR/ifmt-bad-arg.rs:84:15
|
LL | println!("{} {:07$} {}", 1, 3.2, 4);
| ^^ ^^---^ ^^
| |
| this width flag expects an `usize` argument at position 7, but there are 3 arguments
|
= note: positional arguments are zero-based
= note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
```
Instead of
```
mod allocator_abi { /* methods */ }
```
we now generate
```
const _: () = { /* methods */ }
```
and use `std_path` for paths referring to standard library entities.
This way we no longer need to generate `use` and `extern crate` imports, and `#[global_allocator]` starts working inside unnamed blocks.
add rustc_private as a proper language feature gate
At the moment, `rustc_private` as a (library) feature exists by
accident: `char::is_xid_start`, `char::is_xid_continue` methods in
libcore define it.
cc https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/How.20to.20declare.20new.20langauge.20feature.3F
I don't know if this is at all reasonable, but at least tests seem to pass locally. That probably means that we can remove/rename to something more resonable the feature in libcore in the next release?
Specific error for positional args after named args in `format!()`
When writing positional arguments after named arguments in the
`format!()` and `println!()` macros, provide a targeted diagnostic.
Follow up to https://github.com/rust-lang/rust/pull/57522/files#r247278885
Creating a fresh expansion and immediately generating a span from it is the most common scenario.
Also avoid allocating `allow_internal_unstable` lists for derive markers repeatedly.
And rename `ExpnInfo::with_unstable` to `ExpnInfo::allow_unstable`, seems to be a better fitting name.
The expansions were created to allow unstable things inside `#[test_case/test/bench]`, but that's not a proper way to do that.
Put the required `allow_internal_unstable`s into the macros' properties instead.
