fix issues and ui tests, address reviews
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Deadbeef
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10 changed files with 72 additions and 25 deletions
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@ -774,8 +774,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
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// Attempting to call a trait method?
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if let Some(trait_did) = tcx.trait_of_assoc(callee) {
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// We can't determine the actual callee here, so we have to do different checks
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// than usual.
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// We can't determine the actual callee (the underlying impl of the trait) here, so we have
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// to do different checks than usual.
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trace!("attempting to call a trait method");
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let is_const = tcx.constness(callee) == hir::Constness::Const;
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@ -1333,7 +1333,7 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
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rustc_non_const_trait_method, AttributeType::Normal, template!(Word),
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ErrorFollowing, EncodeCrossCrate::No,
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"`#[rustc_non_const_trait_method]` should only used by the standard library to mark trait methods \
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as non-const to allow large traits to easier transition to const"
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as non-const to allow large traits an easier transition to const"
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),
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BuiltinAttribute {
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@ -218,7 +218,7 @@ fn compare_method_predicate_entailment<'tcx>(
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trait_m_predicates.instantiate_own(tcx, trait_to_impl_args).map(|(predicate, _)| predicate),
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);
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let is_conditionally_const = tcx.is_conditionally_const(impl_def_id);
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let is_conditionally_const = tcx.is_conditionally_const(impl_m.def_id);
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if is_conditionally_const {
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// Augment the hybrid param-env with the const conditions
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// of the impl header and the trait method.
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@ -2087,7 +2087,10 @@ impl<'tcx> TyCtxt<'tcx> {
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self.constness(def_id) == hir::Constness::Const
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}
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DefKind::Impl { of_trait: true } => {
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self.constness(self.trait_item_of(def_id).unwrap()) == hir::Constness::Const
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let Some(trait_method_did) = self.trait_item_of(def_id) else {
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return false;
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};
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self.constness(trait_method_did) == hir::Constness::Const
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&& self.is_conditionally_const(parent_def_id)
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}
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DefKind::Trait => {
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@ -199,7 +199,7 @@
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- [Inference details](./opaque-types-impl-trait-inference.md)
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- [Return Position Impl Trait In Trait](./return-position-impl-trait-in-trait.md)
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- [Region inference restrictions](./borrow-check/opaque-types-region-inference-restrictions.md)
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- [Const condition checking](./effects.md)
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- [Const traits and const condition checking](./effects.md)
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- [Pattern and exhaustiveness checking](./pat-exhaustive-checking.md)
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- [Unsafety checking](./unsafety-checking.md)
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- [MIR dataflow](./mir/dataflow.md)
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@ -1,4 +1,4 @@
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# Effects and const condition checking
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# Effects, const traits, and const condition checking
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## The `HostEffect` predicate
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@ -154,3 +154,18 @@ be dropped at compile time.
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[old solver]: https://doc.rust-lang.org/nightly/nightly-rustc/src/rustc_trait_selection/traits/effects.rs.html
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[new trait solver]: https://doc.rust-lang.org/nightly/nightly-rustc/src/rustc_next_trait_solver/solve/effect_goals.rs.html
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## More on const traits
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To be expanded later.
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### The `#[rustc_non_const_trait_method]` attribute
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This is intended for internal (standard library) usage only. With this attribute
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applied to a trait method, the compiler will not check the default body of this
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method for ability to run in compile time. Users of the trait will also not be
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allowed to use this trait method in const contexts. This attribute is primarily
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used for constifying large traits such as `Iterator` without having to make all
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its methods `const` at the same time.
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This attribute should not be present while stabilizing the trait as `const`.
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@ -6,7 +6,7 @@ LL | #[rustc_non_const_trait_method]
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= help: add `#![feature(rustc_attrs)]` to the crate attributes to enable
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= note: the `#[rustc_non_const_trait_method]` attribute is an internal implementation detail that will never be stable
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= note: `#[rustc_non_const_trait_method]` should only used by the standard library to mark trait methods as non-const to allow large traits to easier transition to const
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= note: `#[rustc_non_const_trait_method]` should only used by the standard library to mark trait methods as non-const to allow large traits an easier transition to const
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error: aborting due to 1 previous error
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@ -10,6 +10,17 @@ impl const A for () {
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fn a() {}
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}
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impl const A for u8 {
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fn a() {}
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fn b() { println!("hello"); }
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//~^ ERROR: cannot call non-const function
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}
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impl const A for i8 {
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fn a() {}
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fn b() {}
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}
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const fn foo<T: [const] A>() {
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T::a();
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T::b();
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@ -17,6 +28,12 @@ const fn foo<T: [const] A>() {
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<()>::a();
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<()>::b();
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//~^ ERROR: cannot call non-const associated function
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u8::a();
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u8::b();
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//~^ ERROR: cannot call non-const associated function
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i8::a();
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i8::b();
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//~^ ERROR: cannot call non-const associated function
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}
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fn main() {}
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@ -1,5 +1,15 @@
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error[E0015]: cannot call non-const function `std::io::_print` in constant functions
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--> $DIR/no-const-callers.rs:15:14
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LL | fn b() { println!("hello"); }
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| ^^^^^^^^^^^^^^^^^
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note: function `_print` is not const
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--> $SRC_DIR/std/src/io/stdio.rs:LL:COL
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= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
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error[E0015]: cannot call non-const associated function `<T as A>::b` in constant functions
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--> $DIR/no-const-callers.rs:15:5
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--> $DIR/no-const-callers.rs:26:5
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LL | T::b();
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| ^^^^^^
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@ -7,13 +17,29 @@ LL | T::b();
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= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
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error[E0015]: cannot call non-const associated function `<() as A>::b` in constant functions
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--> $DIR/no-const-callers.rs:18:5
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--> $DIR/no-const-callers.rs:29:5
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LL | <()>::b();
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| ^^^^^^^^^
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= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
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error: aborting due to 2 previous errors
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error[E0015]: cannot call non-const associated function `<u8 as A>::b` in constant functions
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--> $DIR/no-const-callers.rs:32:5
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LL | u8::b();
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| ^^^^^^^
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= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
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error[E0015]: cannot call non-const associated function `<i8 as A>::b` in constant functions
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--> $DIR/no-const-callers.rs:35:5
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LL | i8::b();
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| ^^^^^^^
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= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
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error: aborting due to 5 previous errors
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For more information about this error, try `rustc --explain E0015`.
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@ -684,13 +684,6 @@ error[E0015]: cannot call non-const method `<std::ops::Range<i32> as Iterator>::
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LL | const _: _ = (1..10).filter(|x| x % 2 == 0).map(|x| x * x);
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| ^^^^^^^^^^^^^^^^^^^^^^
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note: method `filter` is not const because trait `Iterator` is not const
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--> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
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= note: this trait is not const
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::: $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
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= note: this method is not const
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= note: calls in constants are limited to constant functions, tuple structs and tuple variants
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error[E0015]: cannot call non-const method `<Filter<std::ops::Range<i32>, {closure@$DIR/typeck_type_placeholder_item.rs:240:29: 240:32}> as Iterator>::map::<i32, {closure@$DIR/typeck_type_placeholder_item.rs:240:49: 240:52}>` in constants
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@ -699,13 +692,6 @@ error[E0015]: cannot call non-const method `<Filter<std::ops::Range<i32>, {closu
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LL | const _: _ = (1..10).filter(|x| x % 2 == 0).map(|x| x * x);
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| ^^^^^^^^^^^^^^
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note: method `map` is not const because trait `Iterator` is not const
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--> $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
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= note: this trait is not const
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::: $SRC_DIR/core/src/iter/traits/iterator.rs:LL:COL
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= note: this method is not const
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= note: calls in constants are limited to constant functions, tuple structs and tuple variants
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error: aborting due to 83 previous errors
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