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Auto merge of #87194 - eddyb:const-value-mangling, r=michaelwoerister,oli-obk

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rustc_symbol_mangling: support structural constants and &str in v0.

This PR should unblock #85530 (except for float `const` generics, which AFAIK should've never worked).
(cc `@tmiasko` could the https://github.com/rust-lang/rust/pull/85530#issuecomment-857855379 failures be retried with a quick crater "subset" run of this PR + changing the default to `v0`? Just to make sure I didn't miss anything other than the floats)

The encoding is the one suggested before in e.g. https://github.com/rust-lang/rust/issues/61486#issuecomment-878932102, tho this PR won't by itself finish #61486, before closing that we'd likely want to move to `@oli-obk's` "valtrees" (i.e. #83234 and other associated work).

<hr>

**EDITs**:
1. switched unit/tuple/braced-with-named-fields `<const-fields>` prefixes from `"u"`/`"T"`/`""` to `"U"`/`"T"`/`"S"` to avoid the ambiguity reported by `@tmiasko` in https://github.com/rust-lang/rust/pull/87194#issuecomment-884279921.

2. `rustc-demangle` PR: https://github.com/alexcrichton/rustc-demangle/pull/55

3. RFC amendment PR: https://github.com/rust-lang/rfcs/pull/3161
    * also removed the grammar changes included in that PR, from this description

4. added tests (temporarily using my fork of `rustc-demangle`)

<hr>

r? `@michaelwoerister`
This commit is contained in:
bors 2021-08-26 19:15:09 +00:00
commit ad02dc46ba
21 changed files with 609 additions and 63 deletions
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17
compiler/rustc_middle/src/ty/print/pretty.rs
View file

@ -1220,13 +1220,20 @@ pub trait PrettyPrinter<'tcx>:
}
p!(")");
}
ty::Adt(def, substs) if def.variants.is_empty() => {
p!(print_value_path(def.did, substs));
ty::Adt(def, _) if def.variants.is_empty() => {
self = self.typed_value(
|mut this| {
write!(this, "unreachable()")?;
Ok(this)
},
|this| this.print_type(ty),
": ",
)?;
}
ty::Adt(def, substs) => {
let variant_id =
contents.variant.expect("destructed const of adt without variant id");
let variant_def = &def.variants[variant_id];
let variant_idx =
contents.variant.expect("destructed const of adt without variant idx");
let variant_def = &def.variants[variant_idx];
p!(print_value_path(variant_def.def_id, substs));
match variant_def.ctor_kind {