followed by a semicolon.
This allows code like `vec![1i, 2, 3].len();` to work.
This breaks code that uses macros as statements without putting
semicolons after them, such as:
fn main() {
...
assert!(a == b)
assert!(c == d)
println(...);
}
It also breaks code that uses macros as items without semicolons:
local_data_key!(foo)
fn main() {
println("hello world")
}
Add semicolons to fix this code. Those two examples can be fixed as
follows:
fn main() {
...
assert!(a == b);
assert!(c == d);
println(...);
}
local_data_key!(foo);
fn main() {
println("hello world")
}
RFC #378.
Closes#18635.
[breaking-change]
This change makes the compiler no longer infer whether types (structures
and enumerations) implement the `Copy` trait (and thus are implicitly
copyable). Rather, you must implement `Copy` yourself via `impl Copy for
MyType {}`.
A new warning has been added, `missing_copy_implementations`, to warn
you if a non-generic public type has been added that could have
implemented `Copy` but didn't.
For convenience, you may *temporarily* opt out of this behavior by using
`#![feature(opt_out_copy)]`. Note though that this feature gate will never be
accepted and will be removed by the time that 1.0 is released, so you should
transition your code away from using it.
This breaks code like:
#[deriving(Show)]
struct Point2D {
x: int,
y: int,
}
fn main() {
let mypoint = Point2D {
x: 1,
y: 1,
};
let otherpoint = mypoint;
println!("{}{}", mypoint, otherpoint);
}
Change this code to:
#[deriving(Show)]
struct Point2D {
x: int,
y: int,
}
impl Copy for Point2D {}
fn main() {
let mypoint = Point2D {
x: 1,
y: 1,
};
let otherpoint = mypoint;
println!("{}{}", mypoint, otherpoint);
}
This is the backwards-incompatible part of #13231.
Part of RFC #3.
[breaking-change]
As an example of what this changes, the following code:
```rust
let x: [int ..4];
```
Currently spits out ‘expected `]`, found `..`’. However, a comma would also be valid there, as would a number of other tokens. This change adjusts the parser to produce more accurate errors, so that that example now produces ‘expected one of `(`, `+`, `,`, `::`, or `]`, found `..`’.
(Thanks to cramer on IRC for pointing out this problem with diagnostics.)
The only other place I know of that doesn’t allow trailing commas is closure types (#19414), and those are a bit tricky to fix (I suspect it might be impossible without infinite lookahead) so I didn’t implement that in this patch. There are other issues surrounding closure type parsing anyway, in particular #19410.
As an example of what this changes, the following code:
let x: [int ..4];
Currently spits out ‘expected `]`, found `..`’. However, a comma would also be
valid there, as would a number of other tokens. This change adjusts the parser
to produce more accurate errors, so that that example now produces ‘expected one
of `(`, `+`, `,`, `::`, or `]`, found `..`’.
This breaks code like
```
let t = (42i, 42i);
... t.0::<int> ...;
```
Change this code to not contain an unused type parameter. For example:
```
let t = (42i, 42i);
... t.0 ...;
```
Closes https://github.com/rust-lang/rust/issues/19096
[breaking-change]
Use the expected type to infer the argument/return types of unboxed closures. Also, in `||` expressions, use the expected type to decide if the result should be a boxed or unboxed closure (and if an unboxed closure, what kind).
This supercedes PR #19089, which was already reviewed by @pcwalton.
Futureproof Rust for fancier suffixed literals. The Rust compiler tokenises a literal followed immediately (no whitespace) by an identifier as a single token: (for example) the text sequences `"foo"bar`, `1baz` and `1u1024` are now a single token rather than the pairs `"foo"` `bar`, `1` `baz` and `1u` `1024` respectively.
The compiler rejects all such suffixes in the parser, except for the 12 numeric suffixes we have now.
I'm fairly sure this will affect very few programs, since it's not currently legal to have `<literal><identifier>` in a Rust program, except in a macro invocation. Any macro invocation relying on this behaviour can simply separate the two tokens with whitespace: `foo!("bar"baz)` becomes `foo!("bar" baz)`.
This implements [RFC 463](https://github.com/rust-lang/rfcs/blob/master/text/0463-future-proof-literal-suffixes.md), and so closes https://github.com/rust-lang/rust/issues/19088.
This adds an optional suffix at the end of a literal token:
`"foo"bar`. An actual use of a suffix in a expression (or other literal
that the compiler reads) is rejected in the parser.
This doesn't switch the handling of numbers to this system, and doesn't
outlaw illegal suffixes for them yet.
Came up on IRC that this was a bit unhelpful as to what should actually be *done*. I am new to changing compiler messages, please let me know if there's anything else that needs to be done to accomadate this change.
(My build system is still constantly crashing [Is bors contagious?], so this hasn't been formally `check`ed. I figure it's a simple enough change that any consequences [like compile-fail expected messages?] can be eyeballed by someone more experienced.)
This breaks code that referred to variant names in the same namespace as
their enum. Reexport the variants in the old location or alter code to
refer to the new locations:
```
pub enum Foo {
A,
B
}
fn main() {
let a = A;
}
```
=>
```
pub use self::Foo::{A, B};
pub enum Foo {
A,
B
}
fn main() {
let a = A;
}
```
or
```
pub enum Foo {
A,
B
}
fn main() {
let a = Foo::A;
}
```
[breaking-change]
This implements a considerable portion of rust-lang/rfcs#369 (tracked in #18640). Some interpretations had to be made in order to get this to work. The breaking changes are listed below:
[breaking-change]
- `core::num::{Num, Unsigned, Primitive}` have been deprecated and their re-exports removed from the `{std, core}::prelude`.
- `core::num::{Zero, One, Bounded}` have been deprecated. Use the static methods on `core::num::{Float, Int}` instead. There is no equivalent to `Zero::is_zero`. Use `(==)` with `{Float, Int}::zero` instead.
- `Signed::abs_sub` has been moved to `std::num::FloatMath`, and is no longer implemented for signed integers.
- `core::num::Signed` has been removed, and its methods have been moved to `core::num::Float` and a new trait, `core::num::SignedInt`. The methods now take the `self` parameter by value.
- `core::num::{Saturating, CheckedAdd, CheckedSub, CheckedMul, CheckedDiv}` have been removed, and their methods moved to `core::num::Int`. Their parameters are now taken by value. This means that
- `std::time::Duration` no longer implements `core::num::{Zero, CheckedAdd, CheckedSub}` instead defining the required methods non-polymorphically.
- `core::num::{zero, one, abs, signum}` have been deprecated. Use their respective methods instead.
- The `core::num::{next_power_of_two, is_power_of_two, checked_next_power_of_two}` functions have been deprecated in favor of methods defined a new trait, `core::num::UnsignedInt`
- `core::iter::{AdditiveIterator, MultiplicativeIterator}` are now only implemented for the built-in numeric types.
- `core::iter::{range, range_inclusive, range_step, range_step_inclusive}` now require `core::num::Int` to be implemented for the type they a re parametrized over.
Adds a method for printing a fatal error and also a help message to the
parser and uses this in a variety of places to improve error messages.
Closes#12213.
This common representation for delimeters should make pattern matching easier. Having a separate `token::DelimToken` enum also allows us to enforce the invariant that the opening and closing delimiters must be the same in `ast::TtDelimited`, removing the need to ensure matched delimiters when working with token trees.
https://github.com/rust-lang/rfcs/pull/221
The current terminology of "task failure" often causes problems when
writing or speaking about code. You often want to talk about the
possibility of an operation that returns a Result "failing", but cannot
because of the ambiguity with task failure. Instead, you have to speak
of "the failing case" or "when the operation does not succeed" or other
circumlocutions.
Likewise, we use a "Failure" header in rustdoc to describe when
operations may fail the task, but it would often be helpful to separate
out a section describing the "Err-producing" case.
We have been steadily moving away from task failure and toward Result as
an error-handling mechanism, so we should optimize our terminology
accordingly: Result-producing functions should be easy to describe.
To update your code, rename any call to `fail!` to `panic!` instead.
Assuming you have not created your own macro named `panic!`, this
will work on UNIX based systems:
grep -lZR 'fail!' . | xargs -0 -l sed -i -e 's/fail!/panic!/g'
You can of course also do this by hand.
[breaking-change]
This should be clearer, and fits in better with the `TTNonterminal` variant.
Renames:
- `TTTok` -> `TTToken`
- `TTDelim` -> `TTDelimited`
- `TTSeq` -> `TTSequence`
This came up when working [on the gl-rs generator extension](990383de80/src/gl_generator/lib.rs (L135-L146)).
The new definition of `TTDelim` adds an associated `Span` that covers the whole token tree and enforces the invariant that a delimited sequence of token trees must have an opening and closing delimiter.
A `get_span` method has also been added to `TokenTree` type to make it easier to implement better error messages for syntax extensions.
Spring cleaning is here! In the Fall! This commit removes quite a large amount
of deprecated functionality from the standard libraries. I tried to ensure that
only old deprecated functionality was removed.
This is removing lots and lots of deprecated features, so this is a breaking
change. Please consult the deprecation messages of the deleted code to see how
to migrate code forward if it still needs migration.
[breaking-change]
This adds ‘help’ diagnostic messages to rustc. This is used for anything that provides help to the user, particularly the `--explain` messages that were previously integrated into the relevant error message.
They look like this:
```
match.rs:10:13: 10:14 error: unreachable pattern [E0001]
match.rs:10 1 => {},
^
match.rs:3:1: 3:38 note: in expansion of foo!
match.rs:7:5: 20:2 note: expansion site
match.rs:10:13: 10:14 help: pass `--explain E0001` to see a detailed explanation
```
(`help` is coloured cyan.) Adding these errors on a separate line stops the lines from being too long, as discussed in #16619.
This change is an implementation of [RFC 69][rfc] which adds a third kind of
global to the language, `const`. This global is most similar to what the old
`static` was, and if you're unsure about what to use then you should use a
`const`.
The semantics of these three kinds of globals are:
* A `const` does not represent a memory location, but only a value. Constants
are translated as rvalues, which means that their values are directly inlined
at usage location (similar to a #define in C/C++). Constant values are, well,
constant, and can not be modified. Any "modification" is actually a
modification to a local value on the stack rather than the actual constant
itself.
Almost all values are allowed inside constants, whether they have interior
mutability or not. There are a few minor restrictions listed in the RFC, but
they should in general not come up too often.
* A `static` now always represents a memory location (unconditionally). Any
references to the same `static` are actually a reference to the same memory
location. Only values whose types ascribe to `Sync` are allowed in a `static`.
This restriction is in place because many threads may access a `static`
concurrently. Lifting this restriction (and allowing unsafe access) is a
future extension not implemented at this time.
* A `static mut` continues to always represent a memory location. All references
to a `static mut` continue to be `unsafe`.
This is a large breaking change, and many programs will need to be updated
accordingly. A summary of the breaking changes is:
* Statics may no longer be used in patterns. Statics now always represent a
memory location, which can sometimes be modified. To fix code, repurpose the
matched-on-`static` to a `const`.
static FOO: uint = 4;
match n {
FOO => { /* ... */ }
_ => { /* ... */ }
}
change this code to:
const FOO: uint = 4;
match n {
FOO => { /* ... */ }
_ => { /* ... */ }
}
* Statics may no longer refer to other statics by value. Due to statics being
able to change at runtime, allowing them to reference one another could
possibly lead to confusing semantics. If you are in this situation, use a
constant initializer instead. Note, however, that statics may reference other
statics by address, however.
* Statics may no longer be used in constant expressions, such as array lengths.
This is due to the same restrictions as listed above. Use a `const` instead.
[breaking-change]
[rfc]: https://github.com/rust-lang/rfcs/pull/246
This rewrites them to the current `ItemStatic` production of the compiler, but I
want to get this into a snapshot. It will be illegal to use a `static` in a
pattern of a `match` statement, so all those current uses will need to be
rewritten to `const` once it's implemented. This requires that the stage0
snapshot is able to parse `const`.
cc #17718
Modify ast::ExprMatch to include a new value of type ast::MatchSource,
making it easy to tell whether the match was written literally or
produced via desugaring. This allows us to customize error messages
appropriately.
in favor of `move`.
This breaks code that used `move` as an identifier, because it is now a
keyword. Change such identifiers to not use the keyword `move`.
Additionally, this breaks code that was counting on by-value or
by-reference capture semantics for unboxed closures (behind the feature
gate). Change `ref |:|` to `|:|` and `|:|` to `move |:|`.
Part of RFC #63; part of issue #12831.
[breaking-change]
Part of issue #16640. I am leaving this issue open to handle parsing of
higher-rank lifetimes in traits.
This change breaks code that used unboxed closures:
* Instead of `F:|&: int| -> int`, write `F:Fn(int) -> int`.
* Instead of `F:|&mut: int| -> int`, write `F:FnMut(int) -> int`.
* Instead of `F:|: int| -> int`, write `F:FnOnce(int) -> int`.
[breaking-change]
The implementation essentially desugars during type collection and AST
type conversion time into the parameter scheme we have now. Only fully
qualified names--e.g. `<T as Foo>::Bar`--are supported.
This prevents confusing errors when accidentally using an assignment
in an `if` expression. For example:
```rust
fn main() {
let x = 1u;
if x = x {
println!("{}", x);
}
}
```
Previously, this yielded:
```
test.rs:4:16: 4:17 error: expected `:`, found `!`
test.rs:4 println!("{}", x);
^
```
With this change, it now yields:
```
test.rs:3:8: 3:13 error: mismatched types: expected `bool`, found `()` (expected bool, found ())
test.rs:3 if x = x {
^~~~~
```
Closes issue #17283
This adds ‘help’ diagnostic messages to rustc. This is used for anything that
provides help to the user, particularly the `--explain` messages that were
previously integrated into the relevant error message.
type they provide an implementation for.
This breaks code like:
mod foo {
struct Foo { ... }
}
impl foo::Foo {
...
}
Change this code to:
mod foo {
struct Foo { ... }
impl Foo {
...
}
}
Additionally, if you used the I/O path extension methods `stat`,
`lstat`, `exists`, `is_file`, or `is_dir`, note that these methods have
been moved to the the `std::io::fs::PathExtensions` trait. This breaks
code like:
fn is_it_there() -> bool {
Path::new("/foo/bar/baz").exists()
}
Change this code to:
use std::io::fs::PathExtensions;
fn is_it_there() -> bool {
Path::new("/foo/bar/baz").exists()
}
Closes#17059.
RFC #155.
[breaking-change]
This allows code to access the fields of tuples and tuple structs behind the feature gate `tuple_indexing`:
```rust
#![feature(tuple_indexing)]
let x = (1i, 2i);
assert_eq!(x.1, 2);
struct Point(int, int);
let origin = Point(0, 0);
assert_eq!(origin.0, 0);
assert_eq!(origin.1, 0);
```
Implements [RFC 53](https://github.com/rust-lang/rfcs/blob/master/active/0053-tuple-accessors.md). Closes#16950.
This allows code to access the fields of tuples and tuple structs:
let x = (1i, 2i);
assert_eq!(x.1, 2);
struct Point(int, int);
let origin = Point(0, 0);
assert_eq!(origin.0, 0);
assert_eq!(origin.1, 0);
instead of prefix `..`.
This breaks code that looked like:
match foo {
[ first, ..middle, last ] => { ... }
}
Change this code to:
match foo {
[ first, middle.., last ] => { ... }
}
RFC #55.
Closes#16967.
[breaking-change]
For review. Not sure about the link_attrs stuff. Will work on converting all the tests.
extern crate "foobar" as foo;
extern crate foobar as foo;
Implements remaining part of RFC #47.
Addresses issue #16461.
Removed link_attrs from rust.md, they don't appear to be supported by
the parser.
[breaking-change]
1. The internal layout for traits has changed from (vtable, data) to (data, vtable). If you were relying on this in unsafe transmutes, you might get some very weird and apparently unrelated errors. You should not be doing this! Prefer not to do this at all, but if you must, you should use raw::TraitObject rather than hardcoding rustc's internal representation into your code.
2. The minimal type of reference-to-vec-literals (e.g., `&[1, 2, 3]`) is now a fixed size vec (e.g., `&[int, ..3]`) where it used to be an unsized vec (e.g., `&[int]`). If you want the unszied type, you must explicitly give the type (e.g., `let x: &[_] = &[1, 2, 3]`). Note in particular where multiple blocks must have the same type (e.g., if and else clauses, vec elements), the compiler will not coerce to the unsized type without a hint. E.g., `[&[1], &[1, 2]]` used to be a valid expression of type '[&[int]]'. It no longer type checks since the first element now has type `&[int, ..1]` and the second has type &[int, ..2]` which are incompatible.
3. The type of blocks (including functions) must be coercible to the expected type (used to be a subtype). Mostly this makes things more flexible and not less (in particular, in the case of coercing function bodies to the return type). However, in some rare cases, this is less flexible. TBH, I'm not exactly sure of the exact effects. I think the change causes us to resolve inferred type variables slightly earlier which might make us slightly more restrictive. Possibly it only affects blocks with unreachable code. E.g., `if ... { fail!(); "Hello" }` used to type check, it no longer does. The fix is to add a semicolon after the string.
Implements remaining part of RFC #47.
Addresses issue #16461.
Removed link_attrs from rust.md, they don't appear to be supported by
the parser.
Changed all the tests to use the new extern crate syntax
Change pretty printer to use 'as' syntax
These `where` clauses are accepted everywhere generics are currently
accepted and desugar during type collection to the type parameter bounds
we have today.
A new keyword, `where`, has been added. Therefore, this is a breaking
change. Change uses of `where` to other identifiers.
[breaking-change]
r? @nikomatsakis (or whoever)
These `where` clauses are accepted everywhere generics are currently
accepted and desugar during type collection to the type parameter bounds
we have today.
A new keyword, `where`, has been added. Therefore, this is a breaking
change. Change uses of `where` to other identifiers.
[breaking-change]
methods.
This paves the way to associated items by introducing an extra level of
abstraction ("impl-or-trait item") between traits/implementations and
methods. This new abstraction is encoded in the metadata and used
throughout the compiler where appropriate.
There are no functional changes; this is purely a refactoring.
This patch primarily does two things: (1) it prevents lifetimes from
leaking out of unboxed closures; (2) it allows unboxed closure type
notation, call notation, and construction notation to construct closures
matching any of the three traits.
This breaks code that looked like:
let mut f;
{
let x = &5i;
f = |&mut:| *x + 10;
}
Change this code to avoid having a reference escape. For example:
{
let x = &5i;
let mut f; // <-- move here to avoid dangling reference
f = |&mut:| *x + 10;
}
I believe this is enough to consider unboxed closures essentially
implemented. Further issues (for example, higher-rank lifetimes) should
be filed as followups.
Closes#14449.
[breaking-change]
by-reference upvars.
This partially implements RFC 38. A snapshot will be needed to turn this
on, because stage0 cannot yet parse the keyword.
Part of #12381.
meaning `'b outlives 'a`. Syntax currently does nothing but is needed for full
fix to #5763. To use this syntax, the issue_5763_bootstrap feature guard is
required.
The `type_overflow` lint, doesn't catch the overflow for `i64` because
the overflow happens earlier in the parse phase when the `u64` as biggest
possible int gets casted to `i64` , without checking the for overflows.
We can't lint in the parse phase, so a refactoring of the `LitInt` type
was necessary.
The types `LitInt`, `LitUint` and `LitIntUnsuffixed` where merged to one
type `LitInt` which stores it's value as `u64`. An additional parameter was
added which indicate the signedness of the type and the sign of the value.
the CFG for match statements.
There were two bugs in issue #14684. One was simply that the borrow
check didn't know about the correct CFG for match statements: the
pattern must be a predecessor of the guard. This disallows the bad
behavior if there are bindings in the pattern. But it isn't enough to
prevent the memory safety problem, because of wildcards; thus, this
patch introduces a more restrictive rule, which disallows assignments
and mutable borrows inside guards outright.
I discussed this with Niko and we decided this was the best plan of
action.
This breaks code that performs mutable borrows in pattern guards. Most
commonly, the code looks like this:
impl Foo {
fn f(&mut self, ...) {}
fn g(&mut self, ...) {
match bar {
Baz if self.f(...) => { ... }
_ => { ... }
}
}
}
Change this code to not use a guard. For example:
impl Foo {
fn f(&mut self, ...) {}
fn g(&mut self, ...) {
match bar {
Baz => {
if self.f(...) {
...
} else {
...
}
}
_ => { ... }
}
}
}
Sometimes this can result in code duplication, but often it illustrates
a hidden memory safety problem.
Closes#14684.
[breaking-change]
This is done entirely in the libraries for functions up to 16 arguments.
A macro is used so that more arguments can be easily added if we need.
Note that I had to adjust the overloaded call algorithm to not try
calling the overloaded call operator if the callee is a built-in
function type, to prevent loops.
Closes#15448.
This eliminates the last vestige of the `~` syntax.
Instead of `~self`, write `self: Box<TypeOfSelf>`; instead of `mut
~self`, write `mut self: Box<TypeOfSelf>`, replacing `TypeOfSelf` with
the self-type parameter as specified in the implementation.
Closes#13885.
[breaking-change]
except where trait objects are involved.
Part of issue #15349, though I'm leaving it open for trait objects.
Cross borrowing for trait objects remains because it is needed until we
have DST.
This will break code like:
fn foo(x: &int) { ... }
let a = box 3i;
foo(a);
Change this code to:
fn foo(x: &int) { ... }
let a = box 3i;
foo(&*a);
[breaking-change]
This makes two changes to region inference: (1) it allows region
inference to relate early-bound regions; and (2) it allows regions to be
related before variance runs. The former is needed because there is no
relation between the two regions before region substitution happens,
while the latter is needed because type collection has to run before
variance. We assume that, before variance is inferred, that lifetimes
are invariant. This is a conservative overapproximation.
This relates to #13885. This does not remove `~self` from the language
yet, however.
[breaking-change]
This change propagates to many locations, but because of the
Macro Exterminator (or, more properly, the invariant that it
protects), macro invocations can't occur downstream of expansion.
This means that in librustc and librustdoc, extracting the
desired field can simply assume that it can't be a macro
invocation. Functions in ast_util abstract over this check.
Per discussion with @sfackler, refactored the expander to
change the way that exported macros are collected. Specifically,
a crate now contains a side table of spans that exported macros
go into.
This has two benefits. First, the encoder doesn't need to scan through
the expanded crate in order to discover exported macros. Second, the
expander can drop all expanded macros from the crate, with the pleasant
result that a fully expanded crate contains no macro invocations (which
include macro definitions).
Now, the lexer will categorize every byte in its input according to the
grammar. The parser skips over these while parsing, thus avoiding their
presence in the input to syntax extensions.
This removes a bunch of token types. Tokens now store the original, unaltered
numeric literal (that is still checked for correctness), which is parsed into
an actual number later, as needed, when creating the AST.
This can change how syntax extensions work, but otherwise poses no visible
changes.
[breaking-change]
This shuffles things around a bit so that LIT_CHAR and co store an Ident
which is the original, unaltered literal in the source. When creating the AST,
unescape and postprocess them.
This changes how syntax extensions can work, slightly, but otherwise poses no
visible changes. To get a useful value out of one of these tokens, call
`parse::{char_lit, byte_lit, bin_lit, str_lit}`
[breaking-change]
formerly, the self identifier was being discarded during parsing, which
stymies hygiene. The best fix here seems to be to attach a self identifier
to ExplicitSelf_, a change that rippled through the rest of the compiler,
but without any obvious damage.
This updates https://github.com/rust-lang/rust/pull/15075.
Rename `ToStr::to_str` to `ToString::to_string`. The naive renaming ends up with two `to_string` functions defined on strings in the prelude (the other defined via `collections::str::StrAllocating`). To remedy this I removed `StrAllocating::to_string`, making all conversions from `&str` to `String` go through `Show`. This has a measurable impact on the speed of this conversion, but the sense I get from others is that it's best to go ahead and unify `to_string` and address performance for all `to_string` conversions in `core::fmt`. `String::from_str(...)` still works as a manual fast-path.
Note that the patch was done with a script, and ended up renaming a number of other `*_to_str` functions, particularly inside of rustc. All the ones I saw looked correct, and I didn't notice any additional API breakage.
Closes#15046.
closes#13367
[breaking-change] Use `Sized?` to indicate a dynamically sized type parameter or trait (used to be `type`). E.g.,
```
trait Tr for Sized? {}
fn foo<Sized? X: Share>(x: X) {}
```
This was parsed by the parser but completely ignored; not even stored in
the AST!
This breaks code that looks like:
static X: &'static [u8] = &'static [1, 2, 3];
Change this code to the shorter:
static X: &'static [u8] = &[1, 2, 3];
Closes#15312.
[breaking-change]
Rationale: for what appear to be historical reasons only, the PatIdent contains
a Path rather than an Ident. This means that there are many places in the code
where an ident is artificially promoted to a path, and---much more problematically---
a bunch of elements from a path are simply thrown away, which seems like an invitation
to some really nasty bugs.
This commit replaces the Path in a PatIdent with a SpannedIdent, which just contains an ident
and a span.
This change starts denying `*T` in the parser. All code using `*T` should ensure
that the FFI call does indeed take `const T*` on the other side before renaming
the type to `*const T`.
Otherwise, all code can rename `*T` to `*const T`.
[breaking-change]
