For bootstrapping purposes, this commit does not remove all uses of
the keyword "pure" -- doing so would cause the compiler to no longer
bootstrap due to some syntax extensions ("deriving" in particular).
Instead, it makes the compiler ignore "pure". Post-snapshot, we can
remove "pure" from the language.
There are quite a few (~100) borrow check errors that were essentially
all the result of mutable fields or partial borrows of `@mut`. Per
discussions with Niko I think we want to allow partial borrows of
`@mut` but detect obvious footguns. We should also improve the error
message when `@mut` is erroneously reborrowed.
The fix is straight-forward, but there are several changes
while fixing the issue.
1) disallow `mut` keyword when making a new struct
In code base, there are following code,
```rust
struct Foo { mut a: int };
let a = Foo { mut a: 1 };
```
This is because of structural record, which is
deprecated corrently (see issue #3089) In structural
record, `mut` keyword should be allowd to control
mutability. But without structural record, we don't
need to allow `mut` keyword while constructing struct.
2) disallow structural records in parser level
This is related to 1). With structural records, there
is an ambiguity between empty block and empty struct
To solve the problem, I change parser to stop parsing
structural records. I think this is not a problem,
because structural records are not compiled already.
Misc. issues
There is an ambiguity between empty struct vs. empty match stmt.
with following code,
```rust
match x{} {}
```
Two interpretation is possible, which is listed blow
```rust
match (x{}) {} // matching with newly-constructed empty struct
(match x{}) {} // matching with empty enum(or struct) x
// and then empty block
```
It seems that there is no such code in rust code base, but
there is one test which uses empty match statement:
https://github.com/mozilla/rust/blob/incoming/src/test/run-pass/issue-3037.rs
All other cases could be distinguished with look-ahead,
but this can't be. One possible solution is wrapping with
parentheses when matching with an uninhabited type.
```rust
enum what { }
fn match_with_empty(x: what) -> ~str {
match (x) { //use parentheses to remove the ambiguity
}
}
```
I have seen a few people confused on how to explicitly instantiate generic functions, since the syntax differs from C++'s and C#'s, which is probably where most people asking questions about generic functions are coming from. The only use of the `::<T>` syntax in the reference right now is in the section on paths, which is possibly not where someone trying to find out about generic functions is going to start looking. The tutorial doesn't mention it at all, but I think it's all right to make the reference a tiny bit more redundant and avoid stuffing the tutorial with syntax details.
----
The "Generic functions" subsection mentions that generic functions are instantiated based on context, so let's also mention right away (with a link to the #paths section) that an explicit form is available.
This also adds an example that explicitly instantiates a generic function to the function call expression section.
The "Generic functions" subsection mentions that generic functions are
instantiated based on context, so let's also mention right away (with a
link to the #paths section) that an explicit form is available.
This also adds an example to the function call expression section that
explicitly instantiates a generic function.
LinearMap is quite a bit faster, and is fully owned/sendable without
requiring copies. The older std::map also doesn't use explicit self and
relies on mutable fields.
Changes:
- Refactor move mode computation
- Removes move mode arguments, unary move, capture clauses
(though they still parse for backwards compatibility)
- Simplify how moves are handled in trans
- Fix a number of illegal copies that cropped up
- Workaround for bug involving def-ids in params
(see details below)
Future work (I'll open bugs for these...):
- Improve error messages for moves that are due
to bindings
- Add support for moving owned content like a.b.c
to borrow check, test in trans (but I think it'll
"just work")
- Proper fix for def-ids in params
Def ids in params:
Move captures into a map instead of recomputing.
This is a workaround for a larger bug having to do with the def-ids associated
with ty_params, which are not always properly preserved when inlining. I am
not sure of my preferred fix for the larger bug yet. This current fix removes
the only code in trans that I know of which relies on ty_param def-ids, but
feels fragile.
Most notably, I removed the "foldl" example in the section on pure functions,
as IIRC this is no longer something you need an unsafe block for
(pure functions are as pure as their arguments). Feel free to add
an example where an unsafe block really is needed.
