rust/compiler/rustc_infer
Matthias Krüger 01469693de
Rollup merge of #105611 - BoxyUwU:more_granular_placeholderification, r=wesleywiser
fold instead of obliterating args

Fixes #105608

we call `const_eval_resolve` on the following constant:
```
def: playground::{impl#0}::and::{constant#0},
substs: [
  ConstKind::Unevaluated {
    def: playground::{impl#0}::and::{constant#0},
    substs: [
      ConstKind::Value(0x0),
      _,
    ]
  }
  _,
],
```
when expanded out to `ConstKind::Expr` there are no infer vars so we attempt to evaluate it after replacing infer vars with garbage, however the current logic for replacing with garbage replaces _the whole arg containing the infer var_ rather than just the infer var. This means that after garbage replacement has occured we attempt to evaluate:
```
def: playground::{impl#0}::and::{constant#0},
substs: [
  PLACEHOLDER,
  PLACEHOLDER,
],
```
Which then leads to ctfe being unable to evaluate the const. With this PR we attempt to evaluate:
```
def: playground::{impl#0}::and::{constant#0},
substs: [
  ConstKind::Unevaluated {
    def: playground::{impl#0}::and::{constant#0},
    substs: [
      ConstKind::Value(0x0),
      PLACEHOLDER,
    ]
  }
  PLACEHOLDER,
],
```
which ctfe _can_ handle.

I am not entirely sure why this function is supposed to replace params with placeholders rather than just inference vars 🤔
2022-12-14 10:31:08 +01:00
..
src Rollup merge of #105611 - BoxyUwU:more_granular_placeholderification, r=wesleywiser 2022-12-14 10:31:08 +01:00
Cargo.toml Migrate OpaqueHiddenType, E0282, E0283, E0284, E0698 2022-08-23 14:47:07 +03:00