reimplement `~const Trait` bounds via a fourth kind of generic param #101900

oli-obk · 2022-09-16T13:12:26Z

tracking issue: #102090

Deduplicate two functions that would soon have been three rust-lang#101900 would have added another copy of this for effects

bors · 2022-09-23T16:50:55Z

☔ The latest upstream changes (presumably #102056) made this pull request unmergeable. Please resolve the merge conflicts.

compiler/rustc_feature/src/active.rs

oli-obk · 2022-09-29T10:06:43Z

Looks like src/tools/jsondoclint is not covered by ./x.py check

bors · 2022-09-29T14:05:43Z

☔ The latest upstream changes (presumably #102461) made this pull request unmergeable. Please resolve the merge conflicts.

lcnr · 2023-01-12T12:17:04Z

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -332,6 +359,16 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
        }
    }

+    if has_constness_effect {


has_host_effect.

lcnr · 2023-01-12T12:37:15Z

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

+        let flags = FlagComputation::for_effect(e);
+        if flags.intersects(self.needs_canonical_flags) { e.super_fold_with(self) } else { e }


why is that not simply happening in the _ => {} branch and we stop explicitly using return for the other branches.

lcnr · 2023-01-12T12:38:38Z

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

+    ) -> ty::Effect<'tcx> {
+        let infcx = self.infcx;
+        let bound_to = infcx.shallow_resolve(effect_var);
+        if bound_to != effect_var {


can you make that an assert instead? shouldn't we shallow resolve in fold_effect already?

lcnr · 2023-01-12T12:39:28Z

compiler/rustc_infer/src/infer/canonical/query_response.rs

+                }
+                GenericArgKind::Effect(result_value) => {
+                    if let ty::EffectValue::Bound(debrujin, b) = result_value.val {
+                        // ...in which case we would set `canonical_vars[0]` to `Some(const X)`.


Some(const x)?

lcnr · 2023-01-12T12:42:36Z

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -753,6 +755,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                    GenericArgKind::Lifetime(_) => 0, // erased
                    GenericArgKind::Type(ty) => self.ty_cost(ty),
                    GenericArgKind::Const(_) => 3, // some non-zero value
+                    GenericArgKind::Effect(_) => 3, // some non-zero value


would put them together with regions, you cannot explicitly mention effects so they don't have a cost

lcnr · 2023-01-12T12:43:32Z

compiler/rustc_infer/src/infer/mod.rs

+                EffectVariableValue::Unknown { .. } => {}
+                EffectVariableValue::Known { .. } => continue,
+            }
+            let value = self.tcx.mk_effect(ty::EffectValue::Rigid { on: true }, origin.effect_kind);


not applying vs ty::EffectValue::Rigid { on: true },. afaict either the function comment or the impl is wrong

lcnr · 2023-01-12T12:52:10Z

compiler/rustc_infer/src/infer/sub.rs

+        b: ty::Effect<'tcx>,
+    ) -> RelateResult<'tcx, ty::Effect<'tcx>> {
+        match (a.val, b.val) {
+            // Any effect matches the rigid "on" effect. For example: `T: ~const Trait` (off) implies `T: Trait` (on)


effects and subtyping seems very sus. What's the default variance for effect parameters?

lcnr · 2023-01-12T12:57:39Z

compiler/rustc_infer/src/traits/util.rs

@@ -185,7 +199,19 @@ impl<'tcx> Elaborator<'tcx> {
                // though conceivably we might.
            }
            ty::PredicateKind::Clause(ty::Clause::Projection(..)) => {
-                // Nothing to elaborate in a projection predicate.
+                // `<T as ~const Trait>::TYPE` implies `<T as Trait>::TYPE`


can you add a comment that this is only correct if the predicate has exactly 1 effect param? If there were multiple params i could imagine us wanting to add all possible combinations of const + ~const.

lcnr · 2023-01-12T13:06:47Z

compiler/rustc_middle/src/ty/generics.rs

+                GenericParamDefKind::Effect { kind } => kind == effect_kind,
+                _ => false,
+            })
+            .or_else(|| tcx.generics_of(self.parent?).effect_param(effect_kind, tcx))


i am not certain whether we will always only have 1 effect param of the same kind, or I can at least imagine future extensions which will break this code.

Can you add a Debug_assert to generics_of whichi check for this?

lcnr · 2023-01-12T13:07:53Z

compiler/rustc_middle/src/ty/instance.rs

@@ -338,6 +338,14 @@ impl<'tcx> Instance<'tcx> {
            ty::GenericParamDefKind::Const { .. } => {
                bug!("Instance::mono: {:?} has const parameters", def_id)
            }
+            ty::GenericParamDefKind::Effect { kind } => {
+                // FIXME: this is necessary for `panic` and friends in the monomorphization collector.


Suggested change

// FIXME: this is necessary for `panic` and friends in the monomorphization collector.

// FIXME(effects): this is necessary for `panic` and friends in the monomorphization collector.

compiler/rustc_middle/src/ty/sty.rs

lcnr · 2023-01-12T13:27:29Z

compiler/rustc_middle/src/ty/visit.rs

+        // hook in here to catch this case (annoying...), but
+        // otherwise we do want to remember to visit the rest of the
+        // effect, as it has types/regions embedded in a lot of other
+        // places.


i don't understand that comment 🤔

I think I copy pasted it from constants without looking at the details

lcnr · 2023-01-12T13:47:37Z

compiler/rustc_trait_selection/src/traits/util.rs

@@ -286,27 +286,42 @@ pub fn closure_trait_ref_and_return_type<'tcx>(
    tcx: TyCtxt<'tcx>,
    fn_trait_def_id: DefId,
    self_ty: Ty<'tcx>,
+    // Make this an array once the effect feature is always active


Suggested change

// Make this an array once the effect feature is always active

// FIXME(effects): Make this an array once the effect feature is always active

lcnr · 2023-01-12T13:47:58Z

compiler/rustc_trait_selection/src/traits/util.rs

+        };
+        let trait_ref = tcx.mk_trait_ref(
+            fn_trait_def_id,
+            // FIXME: have the caller pass the effects here and use them.


Suggested change

// FIXME: have the caller pass the effects here and use them.

// FIXME(effects): have the caller pass the effects here and use them.

lcnr · 2023-01-12T13:48:10Z

compiler/rustc_trait_selection/src/traits/util.rs

 }

 pub fn generator_trait_ref_and_outputs<'tcx>(
    tcx: TyCtxt<'tcx>,
    fn_trait_def_id: DefId,
    self_ty: Ty<'tcx>,
+    // Make this an array once the effect feature is always active


Suggested change

// Make this an array once the effect feature is always active

// FIXME(effects): Make this an array once the effect feature is always active

lcnr · 2023-01-12T13:49:45Z

library/core/src/alloc/layout.rs

    #[inline]
-    pub const fn extend(&self, next: Self) -> Result<(Self, usize), LayoutError> {
+    pub fn extend(&self, next: Self) -> Result<(Self, usize), LayoutError> {


why this change?

lcnr · 2023-01-12T13:50:01Z

library/core/src/array/mod.rs

@@ -354,7 +354,7 @@ where
    type Output = <[T] as Index<I>>::Output;

    #[inline]
-    fn index(&self, index: I) -> &Self::Output {
+    fn index(&self, index: I) -> &<[T] as Index<I>>::Output {


same here, why these libs changes?

Because Self didn't work ^^ I'm still figuring out that part

lcnr · 2023-01-27T11:38:18Z

src/test/ui/rfc-2632-const-trait-impl/inherent-impl.rs


 struct S;
 trait T {}

 impl const S {}
 //~^ ERROR inherent impls cannot be `const`
+//~| ERROR `host` is not constrained


adding an effect param for inherent impls seems bad ui wise ^^

yea I hate everything about it ^^ I'll remove it and just require everyone to repeat trait bounds on the functions for now

apiraino · 2023-02-01T22:38:44Z

If I am correct this can be switched to waiting on author. Feel free to request a review with @rustbot ready, thanks!

@rustbot author

oli-obk · 2023-03-14T22:25:23Z

This PR has become impossible to rebase. I'm starting from scratch on a new branch with a smaller MVP

Various cleanups This PR pulls changes out of rust-lang/rust#101900 that can land on master immediately r? ``@fee1-dead``

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rustbot added T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. labels Sep 16, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 16, 2022

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oli-obk force-pushed the const_trait_take_two branch from 9963569 to 815442a Compare September 16, 2022 16:02

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This was referenced Sep 21, 2022

[WIP] Rework the entire const trait system #96077

Closed

Deduplicate two functions that would soon have been three #102095

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oli-obk force-pushed the const_trait_take_two branch from 6dc21df to c68c262 Compare September 22, 2022 09:35

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Sep 22, 2022

Rollup merge of rust-lang#102095 - oli-obk:simplify, r=TaKO8Ki

fc50878

Deduplicate two functions that would soon have been three rust-lang#101900 would have added another copy of this for effects

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Sep 22, 2022

Rollup merge of rust-lang#102095 - oli-obk:simplify, r=TaKO8Ki

8f4accc

Deduplicate two functions that would soon have been three rust-lang#101900 would have added another copy of this for effects

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Sep 23, 2022

Rollup merge of rust-lang#102095 - oli-obk:simplify, r=TaKO8Ki

dac0f6e

Deduplicate two functions that would soon have been three rust-lang#101900 would have added another copy of this for effects

oli-obk force-pushed the const_trait_take_two branch 2 times, most recently from 3ec01fc to 2e40ec7 Compare September 23, 2022 10:48

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fee1-dead reviewed Sep 28, 2022

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oli-obk force-pushed the const_trait_take_two branch from 098e59c to b98d0d3 Compare September 30, 2022 12:33

oli-obk mentioned this pull request Sep 30, 2022

Allow ~const bounds on non-const functions #102273

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oli-obk force-pushed the const_trait_take_two branch from 37df7dc to 8de7869 Compare October 4, 2022 10:10

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oli-obk mentioned this pull request Jan 20, 2023

add a Callable trait that is implemented for unsafe functions, too #107123

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 1, 2023

felix91gr mentioned this pull request Mar 9, 2023

I wonder if all the methods of the crate could be made const stephaneyfx/enum-iterator#24

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fee1-dead mentioned this pull request Apr 16, 2023

Tracking Issue for removing impl const and ~const in the standard library #110395

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Rollup merge of #105960 - oli-obk:effect_cleanup, r=fee1-dead

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Various cleanups This PR pulls changes out of rust-lang/rust#101900 that can land on master immediately r? ``@fee1-dead``

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reimplement `~const Trait` bounds via a fourth kind of generic param #101900

reimplement `~const Trait` bounds via a fourth kind of generic param #101900

oli-obk commented Sep 16, 2022 •

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oli-obk commented Mar 14, 2023

		let flags = FlagComputation::for_effect(e);
		if flags.intersects(self.needs_canonical_flags) { e.super_fold_with(self) } else { e }

	// FIXME: this is necessary for `panic` and friends in the monomorphization collector.
	// FIXME(effects): this is necessary for `panic` and friends in the monomorphization collector.

	// Make this an array once the effect feature is always active
	// FIXME(effects): Make this an array once the effect feature is always active

	// FIXME: have the caller pass the effects here and use them.
	// FIXME(effects): have the caller pass the effects here and use them.

reimplement ~const Trait bounds via a fourth kind of generic param #101900

reimplement ~const Trait bounds via a fourth kind of generic param #101900

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apiraino commented Feb 1, 2023

oli-obk commented Mar 14, 2023

reimplement `~const Trait` bounds via a fourth kind of generic param #101900

reimplement `~const Trait` bounds via a fourth kind of generic param #101900

oli-obk commented Sep 16, 2022 •

edited

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