From 4e5692d9858d298f27757579688c71ba494cb5c3 Mon Sep 17 00:00:00 2001 From: "Felix S. Klock II" Date: Fri, 18 Jan 2019 12:18:57 +0100 Subject: [PATCH] test that wildcard type `_` is not duplicated by `type Foo = (X, X);` and potentially instantiated at different types. (Updated to reflect changes in diagnostic output and compiletest infrastructure.) --- ...ssue-55748-pat-types-constrain-bindings.rs | 70 +++++++++++++++++++ ...-55748-pat-types-constrain-bindings.stderr | 29 ++++++++ 2 files changed, 99 insertions(+) create mode 100644 src/test/ui/nll/user-annotations/issue-55748-pat-types-constrain-bindings.rs create mode 100644 src/test/ui/nll/user-annotations/issue-55748-pat-types-constrain-bindings.stderr diff --git a/src/test/ui/nll/user-annotations/issue-55748-pat-types-constrain-bindings.rs b/src/test/ui/nll/user-annotations/issue-55748-pat-types-constrain-bindings.rs new file mode 100644 index 0000000000000..3d042d442d531 --- /dev/null +++ b/src/test/ui/nll/user-annotations/issue-55748-pat-types-constrain-bindings.rs @@ -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); + +fn uncoupled_lhs<'a>(_x: &'a u32, s: &'static u32) -> &'static u32 { + let ((mut y, mut _z),): (PairUncoupled,) = ((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) { + ::std::mem::swap(&mut y, &mut _z); +} + +fn coupled_regions_lhs<'a>(_x: &'a u32, s: &'static u32) -> &'static u32 { + let ((y, _z),): (PairCoupledRegions,) = ((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); +} diff --git a/src/test/ui/nll/user-annotations/issue-55748-pat-types-constrain-bindings.stderr b/src/test/ui/nll/user-annotations/issue-55748-pat-types-constrain-bindings.stderr new file mode 100644 index 0000000000000..5929707e41e10 --- /dev/null +++ b/src/test/ui/nll/user-annotations/issue-55748-pat-types-constrain-bindings.stderr @@ -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 +