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test that wildcard type `_` is not duplicated by `type Foo<X> = (X, X…

…);` and potentially instantiated at different types.

(Updated to reflect changes in diagnostic output and compiletest infrastructure.)
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pnkfelix committed Jan 18, 2019
1 parent 8bf1f1c commit 4e5692d9858d298f27757579688c71ba494cb5c3
@@ -0,0 +1,70 @@
// This test is ensuring that type ascriptions on let bindings
// constrain both:
//
// 1. the input expression on the right-hand side (after any potential
// coercion, and allowing for covariance), *and*
//
// 2. the bindings (if any) nested within the pattern on the left-hand
// side (and here, the type-constraint is *invariant*).

#![feature(nll)]

#![allow(dead_code, unused_mut)]
type PairUncoupled<'a, 'b, T> = (&'a T, &'b T);
type PairCoupledRegions<'a, T> = (&'a T, &'a T);
type PairCoupledTypes<T> = (T, T);

fn uncoupled_lhs<'a>(_x: &'a u32, s: &'static u32) -> &'static u32 {
let ((mut y, mut _z),): (PairUncoupled<u32>,) = ((s, &_x),); // ok
// Above compiling does *not* imply below would compile.
// ::std::mem::swap(&mut y, &mut _z);
y
}

fn swap_regions((mut y, mut _z): PairCoupledRegions<u32>) {
::std::mem::swap(&mut y, &mut _z);
}

fn coupled_regions_lhs<'a>(_x: &'a u32, s: &'static u32) -> &'static u32 {
let ((y, _z),): (PairCoupledRegions<u32>,) = ((s, &_x),);
// If above line compiled, so should line below ...

// swap_regions((y, _z));

// ... but the ascribed type also invalidates this use of `y`
y //~ ERROR lifetime may not live long enough
}

fn swap_types((mut y, mut _z): PairCoupledTypes<&u32>) {
::std::mem::swap(&mut y, &mut _z);
}

fn coupled_types_lhs<'a>(_x: &'a u32, s: &'static u32) -> &'static u32 {
let ((y, _z),): (PairCoupledTypes<&u32>,) = ((s, &_x),);
// If above line compiled, so should line below ...

// swap_types((y, _z));

// ... but the ascribed type also invalidates this use of `y`
y //~ ERROR lifetime may not live long enough
}

fn swap_wilds((mut y, mut _z): PairCoupledTypes<&u32>) {
::std::mem::swap(&mut y, &mut _z);
}

fn coupled_wilds_lhs<'a>(_x: &'a u32, s: &'static u32) -> &'static u32 {
let ((y, _z),): (PairCoupledTypes<_>,) = ((s, &_x),);
// If above line compiled, so should line below
// swap_wilds((y, _z));

// ... but the ascribed type also invalidates this use of `y`
y //~ ERROR lifetime may not live long enough
}

fn main() {
uncoupled_lhs(&3, &4);
coupled_regions_lhs(&3, &4);
coupled_types_lhs(&3, &4);
coupled_wilds_lhs(&3, &4);
}
@@ -0,0 +1,29 @@
error: lifetime may not live long enough
--> $DIR/issue-55748-pat-types-constrain-bindings.rs:35:5
|
LL | fn coupled_regions_lhs<'a>(_x: &'a u32, s: &'static u32) -> &'static u32 {
| -- lifetime `'a` defined here
...
LL | y
| ^ returning this value requires that `'a` must outlive `'static`

error: lifetime may not live long enough
--> $DIR/issue-55748-pat-types-constrain-bindings.rs:49:5
|
LL | fn coupled_types_lhs<'a>(_x: &'a u32, s: &'static u32) -> &'static u32 {
| -- lifetime `'a` defined here
...
LL | y
| ^ returning this value requires that `'a` must outlive `'static`

error: lifetime may not live long enough
--> $DIR/issue-55748-pat-types-constrain-bindings.rs:62:5
|
LL | fn coupled_wilds_lhs<'a>(_x: &'a u32, s: &'static u32) -> &'static u32 {
| -- lifetime `'a` defined here
...
LL | y
| ^ returning this value requires that `'a` must outlive `'static`

error: aborting due to 3 previous errors

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