From 0817b1d3ed26898e7d9ed71f6a2218d912ea6de5 Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Tue, 6 Dec 2022 23:55:26 +0000 Subject: [PATCH] Don't deduce a signature that makes a closure cyclic --- compiler/rustc_hir_typeck/src/closure.rs | 38 +++++++++-- src/test/ui/closures/supertrait-hint-cycle.rs | 65 +++++++++++++++++++ src/test/ui/issues/issue-25439.stderr | 21 +++--- .../unboxed-closure-no-cyclic-sig.stderr | 21 +++--- 4 files changed, 122 insertions(+), 23 deletions(-) create mode 100644 src/test/ui/closures/supertrait-hint-cycle.rs diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs index 5bd02dff73b..8167e7e070c 100644 --- a/compiler/rustc_hir_typeck/src/closure.rs +++ b/compiler/rustc_hir_typeck/src/closure.rs @@ -13,7 +13,7 @@ use rustc_macros::{TypeFoldable, TypeVisitable}; use rustc_middle::ty::subst::InternalSubsts; use rustc_middle::ty::visit::TypeVisitable; -use rustc_middle::ty::{self, Ty}; +use rustc_middle::ty::{self, Ty, TypeSuperVisitable, TypeVisitor}; use rustc_span::source_map::Span; use rustc_target::spec::abi::Abi; use rustc_trait_selection::traits; @@ -21,6 +21,7 @@ use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _; use std::cmp; use std::iter; +use std::ops::ControlFlow; /// What signature do we *expect* the closure to have from context? #[derive(Debug, Clone, TypeFoldable, TypeVisitable)] @@ -54,7 +55,7 @@ pub fn check_expr_closure( // closure sooner rather than later, so first examine the expected // type, and see if can glean a closure kind from there. let (expected_sig, expected_kind) = match expected.to_option(self) { - Some(ty) => self.deduce_expectations_from_expected_type(ty), + Some(ty) => self.deduce_closure_signature(ty), None => (None, None), }; let body = self.tcx.hir().body(closure.body); @@ -162,13 +163,14 @@ fn check_closure( /// Given the expected type, figures out what it can about this closure we /// are about to type check: #[instrument(skip(self), level = "debug")] - fn deduce_expectations_from_expected_type( + fn deduce_closure_signature( &self, expected_ty: Ty<'tcx>, ) -> (Option>, Option) { match *expected_ty.kind() { ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => self - .deduce_signature_from_predicates( + .deduce_closure_signature_from_predicates( + expected_ty, self.tcx.bound_explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs), ), ty::Dynamic(ref object_type, ..) => { @@ -181,7 +183,8 @@ fn deduce_expectations_from_expected_type( .and_then(|did| self.tcx.fn_trait_kind_from_def_id(did)); (sig, kind) } - ty::Infer(ty::TyVar(vid)) => self.deduce_signature_from_predicates( + ty::Infer(ty::TyVar(vid)) => self.deduce_closure_signature_from_predicates( + self.tcx.mk_ty_var(self.root_var(vid)), self.obligations_for_self_ty(vid).map(|obl| (obl.predicate, obl.cause.span)), ), ty::FnPtr(sig) => { @@ -192,8 +195,9 @@ fn deduce_expectations_from_expected_type( } } - fn deduce_signature_from_predicates( + fn deduce_closure_signature_from_predicates( &self, + expected_ty: Ty<'tcx>, predicates: impl DoubleEndedIterator, Span)>, ) -> (Option>, Option) { let mut expected_sig = None; @@ -214,13 +218,33 @@ fn deduce_signature_from_predicates( if expected_sig.is_none() && let ty::PredicateKind::Clause(ty::Clause::Projection(proj_predicate)) = bound_predicate.skip_binder() { - expected_sig = self.normalize( + let inferred_sig = self.normalize( obligation.cause.span, self.deduce_sig_from_projection( Some(obligation.cause.span), bound_predicate.rebind(proj_predicate), ), ); + // Make sure that we didn't infer a signature that mentions itself. + // This can happen when we elaborate certain supertrait bounds that + // mention projections containing the `Self` type. See + struct MentionsTy<'tcx> { + expected_ty: Ty<'tcx>, + } + impl<'tcx> TypeVisitor<'tcx> for MentionsTy<'tcx> { + type BreakTy = (); + + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow { + if t == self.expected_ty { + ControlFlow::BREAK + } else { + t.super_visit_with(self) + } + } + } + if inferred_sig.visit_with(&mut MentionsTy { expected_ty }).is_continue() { + expected_sig = inferred_sig; + } } // Even if we can't infer the full signature, we may be able to diff --git a/src/test/ui/closures/supertrait-hint-cycle.rs b/src/test/ui/closures/supertrait-hint-cycle.rs new file mode 100644 index 00000000000..dbb06b2ef7a --- /dev/null +++ b/src/test/ui/closures/supertrait-hint-cycle.rs @@ -0,0 +1,65 @@ +// edition:2021 +// check-pass + +#![feature(type_alias_impl_trait)] +#![feature(closure_lifetime_binder)] + +use std::future::Future; + +trait AsyncFn: FnMut(I) -> Self::Fut { + type Fut: Future; +} + +impl AsyncFn for F +where + Fut: Future, + F: FnMut(I) -> Fut, +{ + type Fut = Fut; +} + +async fn call(mut ctx: C, mut f: F) -> Result +where + F: for<'a> AsyncFn<&'a mut C, Result>, +{ + loop { + match f(&mut ctx).await { + Ok(val) => return Ok(val), + Err(_) => continue, + } + } +} + +trait Cap<'a> {} +impl Cap<'_> for T {} + +fn works(ctx: &mut usize) { + let mut inner = 0; + + type Ret<'a, 'b: 'a> = impl Future> + 'a + Cap<'b>; + + let callback = for<'a, 'b> |c: &'a mut &'b mut usize| -> Ret<'a, 'b> { + inner += 1; + async move { + let _c = c; + Ok(1usize) + } + }; + call(ctx, callback); +} + +fn doesnt_work_but_should(ctx: &mut usize) { + let mut inner = 0; + + type Ret<'a, 'b: 'a> = impl Future> + 'a + Cap<'b>; + + call(ctx, for<'a, 'b> |c: &'a mut &'b mut usize| -> Ret<'a, 'b> { + inner += 1; + async move { + let _c = c; + Ok(1usize) + } + }); +} + +fn main() {} diff --git a/src/test/ui/issues/issue-25439.stderr b/src/test/ui/issues/issue-25439.stderr index 325c28c15e2..938c9d9f18c 100644 --- a/src/test/ui/issues/issue-25439.stderr +++ b/src/test/ui/issues/issue-25439.stderr @@ -1,14 +1,19 @@ -error[E0644]: closure/generator type that references itself - --> $DIR/issue-25439.rs:8:9 +error[E0631]: type mismatch in closure arguments + --> $DIR/issue-25439.rs:8:5 | LL | fix(|_, x| x); - | ^^^^^^^^ cyclic type of infinite size + | ^^^ ------ found signature defined here + | | + | expected due to this | - = note: closures cannot capture themselves or take themselves as argument; - this error may be the result of a recent compiler bug-fix, - see issue #46062 - for more information + = note: expected closure signature `for<'a> fn(Helper<'a, [closure@$DIR/issue-25439.rs:8:9: 8:15]>, i32) -> _` + found closure signature `fn(_, _) -> _` +note: required by a bound in `fix` + --> $DIR/issue-25439.rs:3:33 + | +LL | fn fix(f: F) -> i32 where F: Fn(Helper, i32) -> i32 { + | ^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `fix` error: aborting due to previous error -For more information about this error, try `rustc --explain E0644`. +For more information about this error, try `rustc --explain E0631`. diff --git a/src/test/ui/unboxed-closures/unboxed-closure-no-cyclic-sig.stderr b/src/test/ui/unboxed-closures/unboxed-closure-no-cyclic-sig.stderr index 167479270b5..cfea13c1127 100644 --- a/src/test/ui/unboxed-closures/unboxed-closure-no-cyclic-sig.stderr +++ b/src/test/ui/unboxed-closures/unboxed-closure-no-cyclic-sig.stderr @@ -1,14 +1,19 @@ -error[E0644]: closure/generator type that references itself - --> $DIR/unboxed-closure-no-cyclic-sig.rs:8:7 +error[E0631]: type mismatch in closure arguments + --> $DIR/unboxed-closure-no-cyclic-sig.rs:8:5 | LL | g(|_| { }); - | ^^^^^^^^ cyclic type of infinite size + | ^ --- found signature defined here + | | + | expected due to this | - = note: closures cannot capture themselves or take themselves as argument; - this error may be the result of a recent compiler bug-fix, - see issue #46062 - for more information + = note: expected closure signature `fn(Option<[closure@$DIR/unboxed-closure-no-cyclic-sig.rs:8:7: 8:10]>) -> _` + found closure signature `fn(_) -> _` +note: required by a bound in `g` + --> $DIR/unboxed-closure-no-cyclic-sig.rs:5:24 + | +LL | fn g(_: F) where F: FnOnce(Option) {} + | ^^^^^^^^^^^^^^^^^ required by this bound in `g` error: aborting due to previous error -For more information about this error, try `rustc --explain E0644`. +For more information about this error, try `rustc --explain E0631`.