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Chalkify - Tweak `Clause` definition and HRTBs
r? @nikomatsakis
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Remove all unstable placement features
Closes #22181, #27779. Effectively makes the assortment of placement RFCs (rust-lang/rfcs#470, rust-lang/rfcs#809, rust-lang/rfcs#1228) 'unaccepted'. It leaves `box_syntax` and keeps the `<-` token as recognised by libsyntax.
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I don't know the correct process for unaccepting an unstable feature that was accepted as an RFC so...here's a PR.
Let me preface this by saying I'm not particularly happy about doing this (I know it'll be unpopular), but I think it's the most honest expression of how things stand today. I've been motivated by a [post on reddit](https://www.reddit.com/r/rust/comments/7wrqk2/when_will_box_and_placementin_syntax_be_stable/) which asks when these features will be stable - the features have received little RFC-style design work since the end of 2015 (~2 years ago) and leaving them in limbo confuses people who want to know where they're up to. Without additional design work that needs to happen (see the collection of unresolved questions later in this post) they can't really get stabilised, and I think that design work would be most suited to an RFC rather than (currently mostly unused) experimental features in Rust nightly.
I have my own motivations - it's very simple to 'defeat' placement in debug mode today and I don't want a placement in Rust that a) has no guarantees to work and b) has no plan for in-place serde deserialisation.
There's a quote in [1]: "Ordinarily these uncertainties might lead to the RFC being postponed. [The RFC seems like a promising direction hence we will accept since it] will thus give us immediate experience with the design and help in determining the best final solution.". I propose that there have been enough additional uncertainties raised since then that the original direction is less promising and we should be think about the problem anew.
(a historical note: the first mention of placement (under that name - uninit pointers were earlier) in an RFC AFAIK is [0] in late 2014 (pre-1.0). RFCs since then have built on this base - [1] is a comment in Feb 2015 accepting a more conservative design of the Place* traits - this is back when serde still required aster and seemed to break every other nightly! A lot has changed since then, perhaps placement should too)
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Concrete unresolved questions include:
- making placement work in debug mode [7]
- making placement work for serde/with fallible creation [5], [irlo2], [8]
- trait design:
- opting into not consuming the placer in `Placer::make_place` - [2]
- trait proliferation - [4] (+ others in that thread)
- fallible allocation - [3], [4] (+ others in that thread)
- support for DSTs/unsized structs (if at all) - [1], [6]
More speculative unresolved questions include:
- better trait design with in the context of future language features [irlo1] (Q11), [irlo3]
- interaction between custom allocators and placement [irlo3]
[0] https://github.com/rust-lang/rfcs/pull/470
[1] https://github.com/rust-lang/rfcs/pull/809#issuecomment-73910414
[2] https://github.com/rust-lang/rfcs/issues/1286
[3] https://github.com/rust-lang/rfcs/issues/1315
[4] https://github.com/rust-lang/rust/issues/27779#issuecomment-146711893
[5] https://github.com/rust-lang/rust/issues/27779#issuecomment-285562402
[6] https://github.com/rust-lang/rust/issues/27779#issuecomment-354464938
[7] https://github.com/rust-lang/rust/issues/27779#issuecomment-358025344
[8] https://github.com/rust-lang/rfcs/pull/1228#issuecomment-190825370
[irlo1] https://internals.rust-lang.org/t/placement-nwbi-faq-new-box-in-left-arrow/2789
[irlo2] https://internals.rust-lang.org/t/placement-nwbi-faq-new-box-in-left-arrow/2789/19
[irlo3] https://internals.rust-lang.org/t/lang-team-minutes-feature-status-report-placement-in-and-box/4646
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Extend two-phase borrows to apply to method receiver autorefs
Fixes #48598 by permitting two-phase borrows on the autorefs created when functions and methods.
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Closes #22181, #27779
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Fix stable hashing of AllocIds
r? @michaelwoerister
fixes #49081
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Remove universes from `ty::ParamEnv`
This change was never meant to land. #48407 takes an alternate approach. However, that PR is now blocked on some issues with canonicalization, and rebasing these reverts gets harder each time, so let's just get this bit out of the way now.
r? @nikomatsakis
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For consistency, use AllowTwoPhase everywhere between the frontend and MIR.
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support elision in impl headers
You can now do things like:
```
impl MyTrait<'_> for &u32 { ... }
```
Each `'_` or elided lifetime is a fresh parameter. `'_` and elision are still not permitted in associated type values. (Plausibly we could support that if there is a single input lifetime.) The original lifetime elision RFC was a bit unclear on this point: [as documented here, I think this is the correct interpretation, both because it fits existing impls and it's most analogous to the behavior in fns](https://github.com/rust-lang/rust/issues/15872#issuecomment-338700138).
We do not support elision with deprecated forms:
```
impl MyTrait for std::cell::Ref<u32> { } // ERROR
```
Builds on the in-band lifetime stuff.
r? @cramertj
Fixes #15872
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NLL should identify and respect the lifetime annotations that the user wrote
Part of #47184.
r? @nikomatsakis
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This reverts commit d4df52cacbee5d95e912a43188192a5054d36b4f.
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This commit modifies the UserAssertTy statement to take a canonicalized
type rather than a regular type so that we can handle the case where the
user provided type contains a inference variable.
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Deprecated forms of elision are not supported.
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This commit adds a new attribute to the Rust compiler specific to the wasm
target (and no other targets). The `#[wasm_import_module]` attribute is used to
specify the module that a name is imported from, and is used like so:
#[wasm_import_module = "./foo.js"]
extern {
fn some_js_function();
}
Here the import of the symbol `some_js_function` is tagged with the `./foo.js`
module in the wasm output file. Wasm-the-format includes two fields on all
imports, a module and a field. The field is the symbol name (`some_js_function`
above) and the module has historically unconditionally been `"env"`. I'm not
sure if this `"env"` convention has asm.js or LLVM roots, but regardless we'd
like the ability to configure it!
The proposed ES module integration with wasm (aka a wasm module is "just another
ES module") requires that the import module of wasm imports is interpreted as an
ES module import, meaning that you'll need to encode paths, NPM packages, etc.
As a result, we'll need this to be something other than `"env"`!
Unfortunately neither our version of LLVM nor LLD supports custom import modules
(aka anything not `"env"`). My hope is that by the time LLVM 7 is released both
will have support, but in the meantime this commit adds some primitive
encoding/decoding of wasm files to the compiler. This way rustc postprocesses
the wasm module that LLVM emits to ensure it's got all the imports we'd like to
have in it.
Eventually I'd ideally like to unconditionally require this attribute to be
placed on all `extern { ... }` blocks. For now though it seemed prudent to add
it as an unstable attribute, so for now it's not required (as that'd force usage
of a feature gate). Hopefully it doesn't take too long to "stabilize" this!
cc rust-lang-nursery/rust-wasm#29
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r=michaelwoerister
extend stable hasher to support `CanonicalTy`
Fixes #49043
r? @michaelwoerister
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MVP for chalkification
r? @nikomatsakis
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syntax: Make imports in AST closer to the source and cleanup their parsing
This is a continuation of https://github.com/rust-lang/rust/pull/45846 in some sense.
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Make CodeMap and FileMap thread-safe
r? @michaelwoerister
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Types will no longer default to `()`, instead always defaulting to `!`.
This disables the associated warning and removes the flag from TyTuple
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Backed by a canonicalized query. This computes all the types/regions that need
to be live when the destructor runs (i.e., that the dtor may access).
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It was too easy to get this wrong
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