This is technically a breaking change as it deprecates and unstables
some previously stable apis that were missed in the last round of
deprecations.
[breaking change]
This permits all coercions to be performed in casts, but adds lints to warn in those cases.
Part of this patch moves cast checking to a later stage of type checking. We acquire obligations to check casts as part of type checking where we previously checked them. Once we have type checked a function or module, then we check any cast obligations which have been acquired. That means we have more type information available to check casts (this was crucial to making coercions work properly in place of some casts), but it means that casts cannot feed input into type inference.
[breaking change]
* Adds two new lints for trivial casts and trivial numeric casts, these are warn by default, but can cause errors if you build with warnings as errors. Previously, trivial numeric casts and casts to trait objects were allowed.
* The unused casts lint has gone.
* Interactions between casting and type inference have changed in subtle ways. Two ways this might manifest are:
- You may need to 'direct' casts more with extra type information, for example, in some cases where `foo as _ as T` succeeded, you may now need to specify the type for `_`
- Casts do not influence inference of integer types. E.g., the following used to type check:
```
let x = 42;
let y = &x as *const u32;
```
Because the cast would inform inference that `x` must have type `u32`. This no longer applies and the compiler will fallback to `i32` for `x` and thus there will be a type error in the cast. The solution is to add more type information:
```
let x: u32 = 42;
let y = &x as *const u32;
```
This commit deprecates the `count`, `range` and `range_step` functions
in `iter`, in favor of range notation. To recover all existing
functionality, a new `step_by` adapter is provided directly on `ops::Range`
and `ops::RangeFrom`.
[breaking-change]
There was a buildbot failure recently of an arithmetic overflow in the isaac
module of the rand crate, so I've imported the isaac implementation from
out-of-tree which makes somewhat more liberal usage of the wrapping primitives.
Hopefull this quelches any future overflow!
Rebase and follow-through on work done by @cmr and @aatch.
Implements most of rust-lang/rfcs#560. Errors encountered from the checks during building were fixed.
The checks for division, remainder and bit-shifting have not been implemented yet.
See also PR #20795
cc @Aatch ; cc @nikomatsakis
Regarding the `rand` changes: It is unfortunate that Wrapping(T) does
not support the `+=` operator. We may want to try to fix that before
1.0 to make porting code like this palatable.
Regarding `std::rand`, just arith-overflow in first example from
`std::rand::random()` doc.
Many of the core rust libraries have places that rely on integer
wrapping behaviour. These places have been altered to use the wrapping_*
methods:
* core:#️⃣:sip - A number of macros
* core::str - The `maximal_suffix` method in `TwoWaySearcher`
* rustc::util::nodemap - Implementation of FnvHash
* rustc_back::sha2 - A number of macros and other places
* rand::isaac - Isaac64Rng, changed to use the Wrapping helper type
Some places had "benign" underflow. This is when underflow or overflow
occurs, but the unspecified value is not used due to other conditions.
* collections::bit::Bitv - underflow when `self.nbits` is zero.
* collections:#️⃣:{map,table} - Underflow when searching an empty
table. Did cause undefined behaviour in this case due to an
out-of-bounds ptr::offset based on the underflowed index. However the
resulting pointers would never be read from.
* syntax::ext::deriving::encodable - Underflow when calculating the
index of the last field in a variant with no fields.
These cases were altered to avoid the underflow, often by moving the
underflowing operation to a place where underflow could not happen.
There was one case that relied on the fact that unsigned arithmetic and
two's complement arithmetic are identical with wrapping semantics. This
was changed to use the wrapping_* methods.
Finally, the calculation of variant discriminants could overflow if the
preceeding discriminant was `U64_MAX`. The logic in `rustc::middle::ty`
for this was altered to avoid the overflow completely, while the
remaining places were changed to use wrapping methods. This is because
`rustc::middle::ty::enum_variants` now throws an error when the
calculated discriminant value overflows a `u64`.
This behaviour can be triggered by the following code:
```
enum Foo {
A = U64_MAX,
B
}
```
This commit also implements the remaining integer operators for
Wrapped<T>.
This changes the type of some public constants/statics in libunicode.
Notably some `&'static &'static [(char, char)]` have changed
to `&'static [(char, char)]`. The regexp crate seems to be the
sole user of these, yet this is technically a [breaking-change]
This overlaps with #22276 (I left make check running overnight) but covers a number of additional cases and has a few rewrites where the clones are not even necessary.
This also implements `RandomAccessIterator` for `iter::Cloned`
cc @steveklabnik, you may want to glance at this before #22281 gets the bors treatment
New functions, `slice::from_raw_parts` and `slice::from_raw_parts_mut`,
are added to implement the lifetime convention as agreed in rust-lang/rfcs#556.
The functions `slice::from_raw_buf` and `slice::from_raw_mut_buf` are
left deprecated for the time being.
Holding back on changing the signature of `std::ffi::c_str_to_bytes` as consensus in rust-lang/rfcs#592 is building to replace it with a composition of other functions.
Contribution to #21923.
This was particularly helpful in the time just after OIBIT's
implementation to make sure things that were supposed to be Copy
continued to be, but it's now creates a lot of noise for types that
intentionally don't want to be Copy.
r? @alexcrichton
New functions, slice::from_raw_parts and slice::from_raw_parts_mut,
are added to implement the lifetime convention as agreed in RFC PR #556.
The functions slice::from_raw_buf and slice::from_raw_mut_buf are
left deprecated for the time being.
This was particularly helpful in the time just after OIBIT's
implementation to make sure things that were supposed to be Copy
continued to be, but it's now creates a lot of noise for types that
intentionally don't want to be Copy.
Use the crates.io crate `rand` (version 0.1 should be a drop in
replacement for `std::rand`) and `rand_macros` (`#[derive_Rand]` should
be a drop-in replacement).
[breaking-change]
