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Better print ScalarPair when it is tuple or slice #144686

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Better print ScalarPair when it is tuple or slice #144686

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18 changes: 17 additions & 1 deletion compiler/rustc_const_eval/src/interpret/operand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -213,7 +213,23 @@ impl<Prov: Provenance> std::fmt::Display for ImmTy<'_, Prov> {
write!(f, "{:x}: {}", s, self.layout.ty)
}
Immediate::ScalarPair(a, b) => {
// FIXME(oli-obk): at least print tuples and slices nicely
// Try to print slices nicely first
// It's *only* printed for internal debugging
if let Some(ty) = tcx.lift(self.layout.ty)
&& let ty::Slice(element_ty) = ty.kind()
{
// For slices, the first scalar is the pointer, second is the length
let ptr_str = FmtPrinter::print_string(tcx, Namespace::ValueNS, |cx| {
p(cx, a, Ty::new_ptr(tcx, *element_ty, ty::Mutability::Not))
})?;
let len_str = FmtPrinter::print_string(tcx, Namespace::ValueNS, |cx| {
p(cx, b, tcx.types.usize)
})?;

write!(f, "&[{}; {}]: {}", ptr_str, len_str, ty)?;
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Do you have an example of what this looks like in the end?

It seems like it'll print something like &[ptr; 128] which is confusing because it looks like a slice repeating the pointer 128 times, when actually it is a slice of that length starting at ptr.

return Ok(());
}
// Fallback to the original format if we can't pretty print
write!(f, "({:x}, {:x}): {}", a, b, self.layout.ty)
}
Immediate::Uninit => {
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