Commit 94bdde8327608af23771fbca8486c2e5c189fa1e | zig

author	Rue04 <rue.nolastname@protonmail.com> 2026-08-08 09:49:12+02:00
committer	mlugg <services@mlugg.co.uk> 2026-08-08 09:49:12+02:00
log	94bdde8327608af23771fbca8486c2e5c189fa1e
tree	00cba8e7ac4f7af824723091e24ae9ab1095a4f6
parent	276f2e1b810aef048c3ce324e0977ba2d9ff8200

Sema: fix incorrect compile error for `@as(u32, @trunc(@floor(runtime_float)))`

If I had to guess, `Sema.zirRoundOpType` was probably written when `@trunc` etc. could only have a float as their destination type. As a result, for the ints they can cast to now, they'd expect the expression inside them to be a `comptime_float`, which made `@trunc(@floor(runtime_float))` or `@trunc(@floatFromInt(runtime_int))` impossible.
By changing the returned type in this case to be generic poison, showing we don't know the expected type as *any* float can be converted to an int, `@trunc(@floor(runtime_float))` lowers to effectively `@floor(runtime_float)` and `@trunc(@floatFromInt(runtime_int))` throws the expected error that `@floatFromInt`'s result type is unknown here.

Fixes: https://codeberg.org/ziglang/zig/issues/32111
Co-authored-by: rue04 <rue04@rue04.de>
Reviewed-on: https://codeberg.org/ziglang/zig/pulls/35664

2 files changed, 6 insertions(+), 4 deletions(-)

src
- Sema.zig
test
- behavior
  - cast.zig

src/Sema.zig+4-4

...	...	@@ -25542,10 +25542,10 @@ fn zirRoundOpType(sema: Sema, block: Block, extended: Zir.Inst.Extended.InstDa
25542	25542	return .generic_poison_type;
25543	25543	};
25544	25544
25545		const float_ty = dest_ty.optEuBaseType(zcu);
25546		switch (float_ty.scalarType(zcu).zigTypeTag(zcu)) {
25547		.float, .comptime_float => return .fromType(float_ty),
25548		else => return .comptime_float_type,
	25545	const dest_base_ty = dest_ty.optEuBaseType(zcu);
	25546	switch (dest_base_ty.scalarType(zcu).zigTypeTag(zcu)) {
	25547	.float, .comptime_float => return .fromType(dest_base_ty),
	25548	else => return .generic_poison_type,
25549	25549	}
25550	25550	}
25551	25551

test/behavior/cast.zig+2

...	...	@@ -120,6 +120,7 @@ test "@floatFromInt" {
120	120	try expect(@as(i32, @floor(f)) == k);
121	121	try expect(@as(i32, @ceil(f)) == k);
122	122	try expect(@as(i32, @trunc(f)) == k);
	123	try expect(@as(i32, @trunc(@floor(f))) == k);
123	124	}
124	125	};
125	126	try S.doTheTest();
...	...	@@ -197,6 +198,7 @@ test "@floatFromInt(f80)" {
197	198	try expect(@as(Int, @floor(f)) == k);
198	199	try expect(@as(Int, @ceil(f)) == k);
199	200	try expect(@as(Int, @trunc(f)) == k);
	201	try expect(@as(Int, @trunc(@floor(f))) == k);
200	202	}
201	203	};
202	204	try S.doTheTest(i31);