Closes#25046 (by rejecting the code that causes the ICE) and #24946. I haven't been able to deal with the array size or recursion issues yet for associated consts, though my hope was that the change I made for range match patterns might help with array sizes, too.
This PR is pretty much orthogonal to #25065.
- add feature gate
- add basic tests
- adjust parser to eliminate conflict between `const fn` and associated
constants
- allow `const fn` in traits/trait-impls, but forbid later in type check
- correct some merge conflicts
This should hopefully fix all cast-related ICEs once and for all.
I managed to make diagnostics hate me and give me spurious "decoder error"
- removing $build/tmp/extended-errors seems to fix it.
Since the values are stored in a u64 internally, we need to be mask away the
high bits after applying the ! operator. Otherwise, these bits will be set to
one, causing overflow.
The former stopped making sense when we started interning substs and made
TraitRef a 2-word copy type, and I'm moving the latter into an arena as
they live as long as the type context.
This commit removes all the old casting/generic traits from `std::num` that are
no longer in use by the standard library. This additionally removes the old
`strconv` module which has not seen much use in quite a long time. All generic
functionality has been supplanted with traits in the `num` crate and the
`strconv` module is supplanted with the [rust-strconv crate][rust-strconv].
[rust-strconv]: https://github.com/lifthrasiir/rust-strconv
This is a breaking change due to the removal of these deprecated crates, and the
alternative crates are listed above.
[breaking-change]
The overflow-checking attempts to accommodate early evaluation where
we do not have type information yet.
Also, add fixme note about something that has been bothering me.
Many of the modifications putting in `Box::new` calls also include a
pointer to Issue 22405, which tracks going back to `box <expr>` if
possible in the future.
(Still tried to use `Box<_>` where it sufficed; thus some tests still
have `box_syntax` enabled, as they use a mix of `box` and `Box::new`.)
Precursor for overloaded-`box` and placement-`in`; see Issue 22181.
1. Detect and report arithmetic overflow during const-expr eval.
2. Instead `eval_const_expr_partial` returning `Err(String)`, it now
has a dedicated enum of different cases. The main benefit of this
is the ability to pass along an interpretable payload, namely the
two inputs that caused an overlfow.
I attempted to minimize fallout to error output in tests, but some was
unavoidable. Those changes are in a follow-on commit.
This only replaces the conditional arith-overflow asserts with
unconditional errors from the guts of const-eval; it does *not*
attempt to sanely handle such errors e.g. with a nice error message
from `rustc`. So the same test that led me to add this commit are
still failing, and must be addressed.
There's been some debate over the precise form that these APIs should take, and
they've undergone some changes recently, so these APIs are going to be left
unstable for now to be fleshed out during the next release cycle.
