If the float can store all possible values of the integer without
rounding, coercion is allowed. The integer's precision must be less than
or equal to the float's significand precision.
Closes#18614
This commit expands on the foundations laid by https://github.com/ziglang/zig/pull/23177
and moves even more `Sema`-only functionality from `Value`
to `Sema.arith`. Specifically all shift and bitwise operations,
`@truncate`, `@bitReverse` and `@byteSwap` have been moved and
adapted to the new rules around `undefined`.
Especially the comptime shift operations have been basically
rewritten, fixing many open issues in the process.
New rules applied to operators:
* `<<`, `@shlExact`, `@shlWithOverflow`, `>>`, `@shrExact`: compile error if any operand is undef
* `<<|`, `~`, `^`, `@truncate`, `@bitReverse`, `@byteSwap`: return undef if any operand is undef
* `&`, `|`: Return undef if both operands are undef, turn undef into actual `0xAA` bytes otherwise
Additionally this commit canonicalizes the representation of
aggregates with all-undefined members in the `InternPool` by
disallowing them and enforcing the usage of a single typed
`undef` value instead. This reduces the amount of edge cases
and fixes a bunch of bugs related to partially undefined vecs.
List of operations directly affected by this patch:
* `<<`, `<<|`, `@shlExact`, `@shlWithOverflow`
* `>>`, `@shrExact`
* `&`, `|`, `~`, `^` and their atomic rmw + reduce pendants
* `@truncate`, `@bitReverse`, `@byteSwap`
This use case is handled by ArrayListUnmanaged via the "...Bounded"
method variants, and it's more optimal to share machine code, versus
generating multiple versions of each function for differing array
lengths.
The rule: `pub fn main` owns file descriptors 0, 1, and 2. If you didn't
write `pub fn main()` it is, in general, not your business to print to
stderr.
As written, I think langref's example is actually a poor reason to use
`inline`.
If you have
if (foo(1200, 34) != 1234) {
@compileError("bad");
}
and you want to make sure that the call is executed at compile time, the
right way to fix it is to add comptime
if (comptime foo(1200, 34) != 1234) {
@compileError("bad");
}
and not to make the function `inline`. I _think_ that inlining functions
just to avoid `comptime` at a call-site is an anti-pattern. When the
reader sees `foo(123)` at the call-site, they _expect_ this to be a
runtime call, as that's the normal rule in Zig.
Inline is still necessary when you can't make the _whole_ call
`comptime`, because it has some runtime effects, but you still want
comptime-known result.
A good example here is
inline fn findImportPkgHashOrFatal(b: *Build, comptime asking_build_zig: type, comptime dep_name: []const u8) []const u8 {
from Build.zig, where the `b` argument is runtime, and is used for
side-effects, but where the result is comptime.
I don't know of a good small example to demonstrate the subtelty here,
so I went ahead with just adding a runtime print to `foo`. Hopefully
it'll be enough for motivated reader to appreciate the subtelty!
Basically everything that has a direct replacement or no uses left.
Notable omissions:
- std.ArrayHashMap: Too much fallout, needs a separate cleanup.
- std.debug.runtime_safety: Too much fallout.
- std.heap.GeneralPurposeAllocator: Lots of references to it remain, not
a simple find and replace as "debug allocator" is not equivalent to
"general purpose allocator".
- std.io.Reader: Is being reworked at the moment.
- std.unicode.utf8Decode(): No replacement, needs a new API first.
- Manifest backwards compat options: Removal would break test data used
by TestFetchBuilder.
- panic handler needs to be a namespace: Many tests still rely on it
being a function, needs a separate cleanup.
`castTruncatedData` was a poorly worded error (all shrinking casts
"truncate bits", it's just that we assume those bits to be zext/sext of
the other bits!), and `negativeToUnsigned` was a pointless distinction
which forced the compiler to emit worse code (since two separate safety
checks were required for casting e.g. 'i32' to 'u16') and wasn't even
implemented correctly. This commit combines those safety panics into one
function, `integerOutOfBounds`. The name maybe isn't perfect, but that's
not hugely important; what matters is the new default message, which is
clearer than the old ones: "integer does not fit in destination type".
This reverts commit dea72d15da, reversing
changes made to ab381933c8.
The changeset does not work as advertised and does not have sufficient
test coverage.
Reopens#22822
