Add AST validation pass and move some checks to it
The purpose of this pass is to catch constructions that fit into AST data structures, but not permitted by the language. As an example, `impl`s don't have visibilities, but for convenience and uniformity with other items they are represented with a structure `Item` which has `Visibility` field.
This pass is intended to run after expansion of macros and syntax extensions (and before lowering to HIR), so it can catch erroneous constructions that were generated by them. This pass allows to remove ad hoc semantic checks from the parser, which can be overruled by syntax extensions and occasionally macros.
The checks can be put here if they are simple, local, don't require results of any complex analysis like name resolution or type checking and maybe don't logically fall into other passes. I expect most of errors generated by this pass to be non-fatal and allowing the compilation to proceed.
I intend to move some more checks to this pass later and maybe extend it with new checks, like, for example, identifier validity. Given that syntax extensions are going to be stabilized in the measurable future, it's important that they would not be able to subvert usual language rules.
In this patch I've added two new checks - a check for labels named `'static` and a check for lifetimes and labels named `'_`. The first one gives a hard error, the second one - a future compatibility warning.
Fixes https://github.com/rust-lang/rust/issues/33059 ([breaking-change])
cc https://github.com/rust-lang/rfcs/pull/1177
r? @nrc
The extra filename and line was mainly there to keep the indentation
relative to the main snippet; now that this doesn't include
filename/line-number as a prefix, it is distracted.
There's a lot of stuff wrong with the representation of these types:
TyFnDef doesn't actually uniquely identify a function, TyFnPtr is used to
represent method calls, TyFnDef in the sub-expression of a cast isn't
correctly reified, and probably some other stuff I haven't discovered yet.
Splitting them seems like the right first step, though.
This PR implements [RFC 1192](https://github.com/rust-lang/rfcs/blob/master/text/1192-inclusive-ranges.md), which is triple-dot syntax for inclusive range expressions. The new stuff is behind two feature gates (one for the syntax and one for the std::ops types). This replaces the deprecated functionality in std::iter. Along the way I simplified the desugaring for all ranges.
This is my first contribution to rust which changes more than one character outside of a test or comment, so please review carefully! Some of the individual commit messages have more of my notes. Also thanks for putting up with my dumb questions in #rust-internals.
- For implementing `std::ops::RangeInclusive`, I took @Stebalien's suggestion from https://github.com/rust-lang/rfcs/pull/1192#issuecomment-137864421. It seemed to me to make the implementation easier and increase type safety. If that stands, the RFC should be amended to avoid confusion.
- I also kind of like @glaebhoerl's [idea](https://github.com/rust-lang/rfcs/pull/1254#issuecomment-147815299), which is unified inclusive/exclusive range syntax something like `x>..=y`. We can experiment with this while everything is behind a feature gate.
- There are a couple of FIXMEs left (see the last commit). I didn't know what to do about `RangeArgument` and I haven't added `Index` impls yet. Those should be discussed/finished before merging.
cc @Gankro since you [complained](https://www.reddit.com/r/rust/comments/3xkfro/what_happened_to_inclusive_ranges/cy5j0yq)
cc #27777#30877rust-lang/rust#1192rust-lang/rfcs#1254
relevant to #28237 (tracking issue)
A whole bunch of stuff gets folded into struct handling! Plus, removes
an ugly hack from trans and accidentally fixes a bug with constructing
ranges from references (see later commits with tests).
cc https://github.com/rust-lang/rust/pull/31487#issuecomment-182945101
plugin-[breaking-change]
The first commit renames `ast::Pat_` to `ast::PatKind` and uses its variants in enum qualified form. I've also taken the opportunity and renamed `PatKind::Region` into `PatKind::Ref`.
The second commit splits `PatKind::Enum` into `PatKind::TupleStruct` and `PatKind::UnitStruct`.
So, pattern kinds now correspond to their struct/variant kinds - `Struct`, `TupleStruct` and `UnitStruct`.
@nikomatsakis @nrc @arielb1 Are you okay with this naming scheme?
An alternative possible naming scheme is `PatKind::StructVariant`, `PatKind::TupleVariant`, `PatKind::UnitVariant` (it's probably closer to the common use, but I like it less).
I intend to apply these changes to HIR later, they should not necessarily go in the same nightly with https://github.com/rust-lang/rust/pull/31487
r? @Manishearth
<sup>**context:** moving back to a layered approach to type checking.</sup>
It looks like they'd not ended up tightly coupled in the time one was owned by the other. Every instance outside of `FnCtxt.inh` was from an `InferCtxt` created and dropped in the same function body.
This conflicts slightly with #30652, but there too it looks like the `FulfillmentContext` is from an `InferCtxt` that is created and dropped within the same function body (across one call to a module-private function).
That said, I heard that the PR that originally moved `FulfillmentContext` into `InferCtxt` was big, which leaves me concerned that I'm missing something.
r? @nikomatsakis
r? @brson
cc @alexcrichton
I still need to add error code explanation test with this, but I can't figure out a way to generate the `.md` files in order to test example source codes.
Will fix#27328.
