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Auto merge of #46722 - arielb1:single-self, r=eddyb

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fix broken assertion in type_param

Nested generics (aka method generics) in trait methods don't have an
*additional* Self parameter in their own type parameter list (they have
a Self parameter in the parent generics), so don't try to check we're
correctly adjusting for it.

Fixes #46568.

r? @eddyb
This commit is contained in:
bors 2017-12-16 09:12:04 +00:00
commit bdae618418
3 changed files with 72 additions and 29 deletions
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28
src/librustc/ty/mod.rs
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@ -787,10 +787,20 @@ impl<'a, 'gcx, 'tcx> Generics {
if let Some(idx) = param.idx.checked_sub(self.parent_count() as u32) {
// non-Self type parameters are always offset by exactly
// `self.regions.len()`. In the absence of a Self, this is obvious,
// but even in the absence of a `Self` we just have to "compensate"
// but even in the presence of a `Self` we just have to "compensate"
// for the regions:
//
// For example, for `trait Foo<'a, 'b, T1, T2>`, the
// Without a `Self` (or in a nested generics that doesn't have
// a `Self` in itself, even through it parent does), for example
// for `fn foo<'a, T1, T2>()`, the situation is:
// Substs:
// 0 1 2
// 'a T1 T2
// generics.types:
// 0 1
// T1 T2
//
// And with a `Self`, for example for `trait Foo<'a, 'b, T1, T2>`, the
// situation is:
// Substs:
// 0 1 2 3 4
@ -798,14 +808,20 @@ impl<'a, 'gcx, 'tcx> Generics {
// generics.types:
// 0 1 2
// Self T1 T2
// And it can be seen that to move from a substs offset to a
// generics offset you just have to offset by the number of regions.
//
// And it can be seen that in both cases, to move from a substs
// offset to a generics offset you just have to offset by the
// number of regions.
let type_param_offset = self.regions.len();
let has_self = self.has_self && self.parent.is_none();
let is_separated_self = type_param_offset != 0 && idx == 0 && has_self;
if let Some(idx) = (idx as usize).checked_sub(type_param_offset) {
assert!(!(self.has_self && idx == 0));
assert!(!is_separated_self, "found a Self after type_param_offset");
&self.types[idx]
} else {
assert!(self.has_self && idx == 0);
assert!(is_separated_self, "non-Self param before type_param_offset");
&self.types[0]
}
} else {