Auto merge of #68679 - matthewjasper:needs-type-op, r=varkor

Improve `ty.needs_drop`

* Handle cycles in `needs_drop` correctly
* Normalize types when computing `needs_drop`
* Move queries from rustc to rustc_ty
* Avoid query in simple cases

reopens #65918
This commit is contained in:
bors 2020-02-12 19:31:49 +00:00
commit a1912f2e89
16 changed files with 337 additions and 163 deletions

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@ -1,4 +1,5 @@
// build-fail
// compile-flags:-C overflow-checks=off
enum Nil {NilValue}
struct Cons<T> {head:isize, tail:T}

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@ -1,5 +1,5 @@
error: reached the recursion limit while instantiating `test::<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Cons<Nil>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
--> $DIR/recursion.rs:14:1
--> $DIR/recursion.rs:15:1
|
LL | / fn test<T:Dot> (n:isize, i:isize, first:T, second:T) ->isize {
LL | | match n { 0 => {first.dot(second)}

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@ -1,3 +1,5 @@
// ignore-test: This now ICEs again.
// build-pass
#![feature(type_alias_impl_trait)]