Pointers to bound variables shouldn't be stored before checking pattern,
otherwise piped patterns can conflict with each other (issue #6338).
Closes#6338.
Rewriting visit.rs to operate on a borrowed `&mut V` where `<V:Visitor>`
r? @nikomatsakis
r? @pcwalton
This is the first in a planned series of incremental pull requests. (There will probably be five pull requests including this one, though they can be combined or split as necessary.)
Part of #7081. (But definitely does *not* complete it, not on its own, and not even after all five parts land; there are still a few loose ends to tie up or trim afterwards.)
The bulk of this change for this particular PR is pnkfelix@3d83010, which has the changes necessary to visit.rs to support everything else that comes later. The other commits are illustrating the standard mechanical transformation that I am applying.
One important point for nearly *all* of these pull requests: I was deliberately *not* trying to be intelligent in the transformation.
* My goal was to minimize code churn, and make the transformation as mechanical as possible.
* For example, I kept the separation between the Visitor struct (corresponding to the earlier vtable of functions that were potentially closed over local state) and the explicitly passed (and clones) visitor Env. I am certain that this is almost always unnecessary, and a later task will be to go through an meld the Env's into the Visitors as appropriate. (My original goal had been to make such melding part of this task; that's why I turned them into a (Env, vtable) tuple way back when. But I digress.)
* Also, my main goal here was to get rid of the record of `@fn`'s as described by the oldvisit.rs API. (This series gets rid of all but one such case; I'm still investigating that.) There is *still* plenty of `@`-boxing left to be removed, I'm sure, and even still some `@fn`'s too; removing all of those is not the goal here; its just to get rid of the encoded protocol of `@fn`'s in the (old)visit API.
To see where things will be going in the future (i.e., to get a sneak-preview of future pull-requests in the series), see:
* https://github.com/pnkfelix/rust/commits/fsk-visitor-vpar-defaults-step1 (that's this one)
* https://github.com/pnkfelix/rust/commits/fsk-visitor-vpar-defaults-step2
* https://github.com/pnkfelix/rust/commits/fsk-visitor-vpar-defaults-step3
* https://github.com/pnkfelix/rust/commits/fsk-visitor-vpar-defaults-step4
* https://github.com/pnkfelix/rust/commits/fsk-visitor-vpar-defaults-step5
* Note that between step 4 and step 5 there is just a single commit, but its a doozy because its the only case where my mechanical transformation did not apply, and thus more serious rewriting was necessary. See commit pnkfelix@da902b2ff3b1e0bee9fc63cf00c449cceea8abf7
If they are on the trait then it is extremely annoying to use them as
generic parameters to a function, e.g. with the iterator param on the trait
itself, if one was to pass an Extendable<int> to a function that filled it
either from a Range or a Map<VecIterator>, one needs to write something
like:
fn foo<E: Extendable<int, Range<int>> +
Extendable<int, Map<&'self int, int, VecIterator<int>>>
(e: &mut E, ...) { ... }
since using a generic, i.e. `foo<E: Extendable<int, I>, I: Iterator<int>>`
means that `foo` takes 2 type parameters, and the caller has to specify them
(which doesn't work anyway, as they'll mismatch with the iterators used in
`foo` itself).
This patch changes it to:
fn foo<E: Extendable<int>>(e: &mut E, ...) { ... }
LLVMConstStringInContext() doesn't need a null-terminated string. It
takes a length instead. Using .to_c_str() here triggers an ICE whenever
the string literal embeds a null, as in "\x00".
.with_c_str() is a replacement for the old .as_c_str(), to avoid
unnecessary boilerplate.
Replace all usages of .to_c_str().with_ref() with .with_c_str().
Alpha-renamed top-level visit_* functions to walk_*.
(Motivation: Distinguish visit action and recursive traversal.)
Abstract over `&mut self` rather than over `@mut self`.
This required some acrobatics, notably the
`impl<E> Visitor<E> for @mut Visitor<E>`
and corresponding introduction of `@mut Visitor` and some local `let
mut` bindings.
Remove oldvisit reference.
Added default implementations for all of the Visitor trait methods.
Note that both `visit_expr_post` and `visit_ty` are no-op's by
default, just like they are in `oldvisit::default_visitor`.
Refactoring: extract logic to ease swapping visit for oldvisit (hopefully).
Replace these with three functions based on iterators: collect, fold,
and fold_. The mapping part is replaced by iterator .map(), so the part
that these functions do is to accumulate the final Result<,> value.
* `result::collect` gathers `Iterator<Result<V, U>>` to `Result<~[V], U>`
* `result::fold` folds `Iterator<Result<T, E>>` to `Result<V, E>`
* `result::fold_` folds `Iterator<Result<T, E>>` to `Result<(), E>`
While looking over the code for object coercion, I realized that it wasn't quite handling freezing and reborrowing correctly. Tweak the code, adding tests for the relevant cases.
r? @pcwalton
This pull request re-implements handling of visibility scopes and source code positions in debug info. It should now be very stable and properly handle
+ variable shadowing
+ expanded code (macros and the new for-loop de-sugaring, for example)
+ variables in the middle of nested scopes
+ bindings declared in the head of match statement arms.
all of which did not work at all or did not work reliably before. Those interested in a more detailed description of the problems at hand, I kindly refer to http://michaelwoerister.github.io/2013/08/03/visibility-scopes.html
Why doesn't the `populate_scope_map()` function use `syntax::visit`?
Because it would not improve this particular AST walker (see: 69dc790849 (commitcomment-3781426))
Cheers,
Michael
