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Auto merge of #88135 - crlf0710:trait_upcasting_part_3, r=nikomatsakis

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Trait upcasting coercion (part 3)

By using separate candidates for each possible choice, this fixes type-checking issues in previous commits.

r? `@nikomatsakis`
This commit is contained in:
bors 2021-08-21 21:14:07 +00:00
commit d3e2578c31
19 changed files with 324 additions and 239 deletions
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15
compiler/rustc_codegen_ssa/src/base.rs
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@ -150,19 +150,8 @@ pub fn unsized_info<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
// trait upcasting coercion
// if both of the two `principal`s are `None`, this function would have returned early above.
// and if one of the two `principal`s is `None`, typechecking would have rejected this case.
let principal_a = data_a
.principal()
.expect("unsized_info: missing principal trait for trait upcasting coercion");
let principal_b = data_b
.principal()
.expect("unsized_info: missing principal trait for trait upcasting coercion");
let vptr_entry_idx = cx.tcx().vtable_trait_upcasting_coercion_new_vptr_slot((
principal_a.with_self_ty(cx.tcx(), source),
principal_b.with_self_ty(cx.tcx(), source),
));
let vptr_entry_idx =
cx.tcx().vtable_trait_upcasting_coercion_new_vptr_slot((source, target));
if let Some(entry_idx) = vptr_entry_idx {
let ptr_ty = cx.type_i8p();