In preparation for upgrading to LLVM 5.0 it looks like we need to tweak how we
cross compile LLVM slightly. It's using `CMAKE_SYSTEM_NAME` to infer whether to
build libFuzzer which only works on some platforms, and then once we configure
that it needs to apparently reach into the host build area to try to compile
`llvm-config` as well. Once these are both configured, though, it looks like we
can successfully cross-compile LLVM.
Implement tokenization for some items in proc_macro
This PR is a partial implementation of https://github.com/rust-lang/rust/issues/43081 targeted towards preserving span information in attribute-like procedural macros. Currently all attribute-like macros will lose span information with the input token stream if it's iterated over due to the inability of the compiler to losslessly tokenize an AST node. This PR takes a strategy of saving off a list of tokens in particular AST nodes to return a lossless tokenized version. There's a few limitations with this PR, however, so the old fallback remains in place.
This is then later used by `proc_macro` to generate a new
`proc_macro::TokenTree` which preserves span information. Unfortunately this
isn't a bullet-proof approach as it doesn't handle the case when there's still
other attributes on the item, especially inner attributes.
Despite this the intention here is to solve the primary use case for procedural
attributes, attached to functions as outer attributes, likely bare. In this
situation we should be able to now yield a lossless stream of tokens to preserve
span information.
improve case with both anonymous lifetime parameters #43269
This is a fix to #43269.
Sample output message-
```
error[E0623]: lifetime mismatch
--> $DIR/ex3-both-anon-regions.rs:12:12
|
11 | fn foo(x: &mut Vec<&u8>, y: &u8) {
| --- --- these references must have the same lifetime
12 | x.push(y);
| ^ data from `y` flows into `x` here
error: aborting due to 2 previous errors
```
r? @nikomatsakis
This test currently fails because the tokenization of an AST item during the
expansion of a procedural macro attribute rounds-trips through strings, losing
span information.
This partly resolves the `FIXME` located in `src/libproc_macro/lib.rs` when
interpreting interpolated tokens. All instances of `ast::Item` which have a list
of tokens attached to them now use that list of tokens to losslessly get
converted into a `TokenTree` instead of going through stringification and losing
span information.
cc #43081
This commit adds a new field to the `Item` AST node in libsyntax to optionally
contain the original token stream that the item itself was parsed from. This is
currently `None` everywhere but is intended for use later with procedural
macros.
The function should accept feature strings that old LLVM might not
support.
Simplify the code using the same approach used by
LLVMRustPrintTargetFeatures.
Dummify the function for non 4.0 LLVM and update the tests accordingly.
Also, remove the explicit code detecting borrows over a yield. It
turns out not to be necessary -- any such borrow winds up with a
lifetime that is part of the generator type, and therefore which will
outlive the generator expression itself, which yields an
`err_out_of_scope`. So instead we intercept those errors and display
them in a nicer way.
