This is accomplished by:
1. Add `MatchMode` enum to `expr_use_visitor`.
2. Computing the match mode for each pattern via a pre-pass, and then
passing the mode along when visiting the pattern in
expr_use_visitor.
3. Adding a `fn matched_pat` callback to expr_use_visitor, which is
called on interior struct and enum nodes of the pattern (as opposed
to `fn consume_pat`, which is only invoked for identifiers at the
leaves of the pattern), and invoking it accordingly.
Of particular interest are the `cat_downcast` instances established
when matching enum variants.
(Previously, scopes were solely identified with NodeId's; this
refactoring prepares for a future where that does not hold.)
Ground work for a proper fix to #8861.
(Previously, statically identifiable scopes/regions were solely
identified with NodeId's; this refactoring prepares for a future
where that 1:1 correspondence does not hold.)
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]
Fixes#18567. `Struct{x:foo, .. with_expr}` did not walk `with_expr`, which allowed
using moved variables in some cases. The CFG for structs also built up with
`with_expr` happening before the fields, which is now reversed. (Fields are now
before the `with_expr` in the CFG)
Fixes#18567. Struct{x:foo, .. with_expr} did not walk with_expr, which allowed
using moved variables in some cases. The CFG for structs also built up with
with_expr happening before the fields, which is now reversed. (Fields are now
before the with_expr in the CFG)
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 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
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.
Change to resolve and update compiler and libs for uses.
[breaking-change]
Enum variants are now in both the value and type namespaces. This means that
if you have a variant with the same name as a type in scope in a module, you
will get a name clash and thus an error. The solution is to either rename the
type or the variant.
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 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);
DST coercions and DST fields in structs
The commits are not quite stand alone, I should probably squash them together before landing. In particular if you review the individual commits, then you'll see some scrappy stuff that gets fixed in later commits. But reading the commits in order might be easier to get an overall idea of what is going on.
The first commit includes putting back time zone into our time library - @pcwalton removed that as part of his de-~str'ing, but I had already converted it to use StrBuf, so we may as well leave it in. Update: no longer, this is removed in a later commit.
[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.
Stop read+write expressions from expanding into two occurences
in the AST. Add a bool to indicate whether an operand in output
position if read+write or not.
Fixes#14936
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.
`for` loop heads.
This breaks code like:
let x = Some(box 1i);
for &a in x.iter() {
}
Change this code to obey the borrow checking rules. For example:
let x = Some(box 1i);
for &ref a in x.iter() {
}
Closes#16205.
[breaking-change]
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]
