From 8b141a24d05c86b4c074715803f0c29783f8f9bc Mon Sep 17 00:00:00 2001
From: Dominik Stolz <d.stolz@tum.de>
Date: Thu, 7 Oct 2021 23:14:33 +0200
Subject: [PATCH 1/3] Add variance constraints for const params
---
.../rustc_typeck/src/variance/constraints.rs | 30 +++++++++++++++----
1 file changed, 25 insertions(+), 5 deletions(-)
diff --git a/compiler/rustc_typeck/src/variance/constraints.rs b/compiler/rustc_typeck/src/variance/constraints.rs
index 1c8ac10818c..33c27ce86dd 100644
--- a/compiler/rustc_typeck/src/variance/constraints.rs
+++ b/compiler/rustc_typeck/src/variance/constraints.rs
@@ -223,8 +223,8 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
self.add_constraints_from_region(current, lt, variance_i)
}
GenericArgKind::Type(ty) => self.add_constraints_from_ty(current, ty, variance_i),
- GenericArgKind::Const(_) => {
- // Consts impose no constraints.
+ GenericArgKind::Const(val) => {
+ self.add_constraints_from_const(current, val, variance_i)
}
}
}
@@ -263,7 +263,8 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
self.add_constraints_from_mt(current, &ty::TypeAndMut { ty, mutbl }, variance);
}
- ty::Array(typ, _) => {
+ ty::Array(typ, len) => {
+ self.add_constraints_from_const(current, len, variance);
self.add_constraints_from_ty(current, typ, variance);
}
@@ -385,13 +386,32 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
self.add_constraints_from_region(current, lt, variance_i)
}
GenericArgKind::Type(ty) => self.add_constraints_from_ty(current, ty, variance_i),
- GenericArgKind::Const(_) => {
- // Consts impose no constraints.
+ GenericArgKind::Const(val) => {
+ self.add_constraints_from_const(current, val, variance)
}
}
}
}
+ /// Adds constraints appropriate for a const expression `val`
+ /// in a context with ambient variance `variance`
+ fn add_constraints_from_const(
+ &mut self,
+ current: &CurrentItem,
+ val: &ty::Const<'tcx>,
+ variance: VarianceTermPtr<'a>,
+ ) {
+ debug!("add_constraints_from_const(val={:?}, variance={:?})", val, variance);
+
+ match &val.val {
+ ty::ConstKind::Unevaluated(uv) => {
+ let substs = uv.substs(self.tcx());
+ self.add_constraints_from_invariant_substs(current, substs, variance);
+ }
+ _ => {}
+ }
+ }
+
/// Adds constraints appropriate for a function with signature
/// `sig` appearing in a context with ambient variance `variance`
fn add_constraints_from_sig(
From 59b36bcfb5fa50b370869f5073a57d514f59e0c8 Mon Sep 17 00:00:00 2001
From: Dominik Stolz <d.stolz@tum.de>
Date: Tue, 12 Oct 2021 21:50:44 +0200
Subject: [PATCH 2/3] Add UI test for the variance of types appearing in consts
---
.../ui/variance/variance-associated-consts.rs | 17 +++++++++++++++++
.../variance/variance-associated-consts.stderr | 10 ++++++++++
2 files changed, 27 insertions(+)
create mode 100644 src/test/ui/variance/variance-associated-consts.rs
create mode 100644 src/test/ui/variance/variance-associated-consts.stderr
diff --git a/src/test/ui/variance/variance-associated-consts.rs b/src/test/ui/variance/variance-associated-consts.rs
new file mode 100644
index 00000000000..da55bc96244
--- /dev/null
+++ b/src/test/ui/variance/variance-associated-consts.rs
@@ -0,0 +1,17 @@
+// Test that the variance computation considers types that
+// appear in const expressions to be invariant.
+
+#![feature(rustc_attrs)]
+#![allow(incomplete_features)]
+#![feature(generic_const_exprs)]
+
+trait Trait {
+ const Const: usize;
+}
+
+#[rustc_variance]
+struct Foo<T: Trait> { //~ ERROR [o]
+ field: [u8; <T as Trait>::Const]
+}
+
+fn main() { }
diff --git a/src/test/ui/variance/variance-associated-consts.stderr b/src/test/ui/variance/variance-associated-consts.stderr
new file mode 100644
index 00000000000..d1bf34781df
--- /dev/null
+++ b/src/test/ui/variance/variance-associated-consts.stderr
@@ -0,0 +1,10 @@
+error[E0208]: [o]
+ --> $DIR/variance-associated-consts.rs:13:1
+ |
+LL | / struct Foo<T: Trait> {
+LL | | field: [u8; <T as Trait>::Const]
+LL | | }
+ | |_^
+
+error: aborting due to previous error
+
From a400f1058e53cf9603e82b7fd00d42df159b8361 Mon Sep 17 00:00:00 2001
From: Dominik Stolz <d.stolz@tum.de>
Date: Tue, 12 Oct 2021 22:47:34 +0200
Subject: [PATCH 3/3] Bless tests
---
.../const-generics/issues/issue-67375.full.stderr | 12 +-----------
src/test/ui/const-generics/issues/issue-67375.rs | 2 +-
.../issues/issue-67945-1.full.stderr | 14 ++------------
src/test/ui/const-generics/issues/issue-67945-1.rs | 2 +-
4 files changed, 5 insertions(+), 25 deletions(-)
diff --git a/src/test/ui/const-generics/issues/issue-67375.full.stderr b/src/test/ui/const-generics/issues/issue-67375.full.stderr
index 0f0e339655b..0cf69879a5c 100644
--- a/src/test/ui/const-generics/issues/issue-67375.full.stderr
+++ b/src/test/ui/const-generics/issues/issue-67375.full.stderr
@@ -8,15 +8,5 @@ LL | inner: [(); { [|_: &T| {}; 0].len() }],
|
= help: consider moving this anonymous constant into a `const` function
-error[E0392]: parameter `T` is never used
- --> $DIR/issue-67375.rs:5:12
- |
-LL | struct Bug<T> {
- | ^ unused parameter
- |
- = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
- = help: if you intended `T` to be a const parameter, use `const T: usize` instead
+error: aborting due to previous error
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0392`.
diff --git a/src/test/ui/const-generics/issues/issue-67375.rs b/src/test/ui/const-generics/issues/issue-67375.rs
index b5b842a15ae..8b4b276bae0 100644
--- a/src/test/ui/const-generics/issues/issue-67375.rs
+++ b/src/test/ui/const-generics/issues/issue-67375.rs
@@ -3,7 +3,7 @@
#![cfg_attr(full, feature(generic_const_exprs))]
struct Bug<T> {
- //~^ ERROR parameter `T` is never used
+ //[min]~^ ERROR parameter `T` is never used
inner: [(); { [|_: &T| {}; 0].len() }],
//[min]~^ ERROR generic parameters may not be used in const operations
//[full]~^^ ERROR overly complex generic constant
diff --git a/src/test/ui/const-generics/issues/issue-67945-1.full.stderr b/src/test/ui/const-generics/issues/issue-67945-1.full.stderr
index 1edc7828caa..8e18fcdffab 100644
--- a/src/test/ui/const-generics/issues/issue-67945-1.full.stderr
+++ b/src/test/ui/const-generics/issues/issue-67945-1.full.stderr
@@ -12,16 +12,6 @@ LL | let x: S = MaybeUninit::uninit();
= note: expected type parameter `S`
found union `MaybeUninit<_>`
-error[E0392]: parameter `S` is never used
- --> $DIR/issue-67945-1.rs:7:12
- |
-LL | struct Bug<S> {
- | ^ unused parameter
- |
- = help: consider removing `S`, referring to it in a field, or using a marker such as `PhantomData`
- = help: if you intended `S` to be a const parameter, use `const S: usize` instead
+error: aborting due to previous error
-error: aborting due to 2 previous errors
-
-Some errors have detailed explanations: E0308, E0392.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/const-generics/issues/issue-67945-1.rs b/src/test/ui/const-generics/issues/issue-67945-1.rs
index 7b7e8428639..99f88bc8e10 100644
--- a/src/test/ui/const-generics/issues/issue-67945-1.rs
+++ b/src/test/ui/const-generics/issues/issue-67945-1.rs
@@ -5,7 +5,7 @@
use std::mem::MaybeUninit;
struct Bug<S> {
- //~^ ERROR parameter `S` is never used
+ //[min]~^ ERROR parameter `S` is never used
A: [(); {
let x: S = MaybeUninit::uninit();
//[min]~^ ERROR generic parameters may not be used in const operations