From c75aeaac0bb2af593b9819cfeae6d518617d48cc Mon Sep 17 00:00:00 2001 From: Deadbeef Date: Thu, 26 Aug 2021 17:58:28 +0000 Subject: [PATCH] Fix #88155 --- .../src/transform/check_consts/check.rs | 82 +++++++++++-------- .../rfc-2632-const-trait-impl/issue-88155.rs | 13 +++ .../issue-88155.stderr | 9 ++ 3 files changed, 68 insertions(+), 36 deletions(-) create mode 100644 src/test/ui/rfc-2632-const-trait-impl/issue-88155.rs create mode 100644 src/test/ui/rfc-2632-const-trait-impl/issue-88155.stderr diff --git a/compiler/rustc_mir/src/transform/check_consts/check.rs b/compiler/rustc_mir/src/transform/check_consts/check.rs index 0361ddc915d4c..0de6d743a7a79 100644 --- a/compiler/rustc_mir/src/transform/check_consts/check.rs +++ b/compiler/rustc_mir/src/transform/check_consts/check.rs @@ -805,6 +805,8 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> { } }; + let mut nonconst_call_permission = false; + // Attempting to call a trait method? if let Some(trait_id) = tcx.trait_of_item(callee) { trace!("attempting to call a trait method"); @@ -824,18 +826,44 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> { ); let implsrc = tcx.infer_ctxt().enter(|infcx| { - let mut selcx = SelectionContext::new(&infcx); - selcx.select(&obligation).unwrap() + let mut selcx = SelectionContext::with_constness(&infcx, hir::Constness::Const); + selcx.select(&obligation) }); - // If the method is provided via a where-clause that does not use the `?const` - // opt-out, the call is allowed. - if let Some(ImplSource::Param(_, hir::Constness::Const)) = implsrc { - debug!( - "const_trait_impl: provided {:?} via where-clause in {:?}", - trait_ref, param_env - ); - return; + match implsrc { + Ok(Some(ImplSource::Param(_, hir::Constness::Const))) => { + debug!( + "const_trait_impl: provided {:?} via where-clause in {:?}", + trait_ref, param_env + ); + return; + } + Ok(Some(ImplSource::UserDefined(data))) => { + let callee_name = tcx.item_name(callee); + if let Some(&did) = tcx.associated_item_def_ids(data.impl_def_id).iter().find(|did| tcx.item_name(**did) == callee_name) { + callee = did; + } + } + _ => { + if !tcx.is_const_fn_raw(callee) { + // At this point, it is only legal when the caller is marked with + // #[default_method_body_is_const], and the callee is in the same + // trait. + let callee_trait = tcx.trait_of_item(callee); + if callee_trait.is_some() { + if tcx.has_attr(caller, sym::default_method_body_is_const) { + if tcx.trait_of_item(caller) == callee_trait { + nonconst_call_permission = true; + } + } + } + + if !nonconst_call_permission { + self.check_op(ops::FnCallNonConst); + return; + } + } + } } // Resolve a trait method call to its concrete implementation, which may be in a @@ -875,34 +903,16 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> { let is_intrinsic = tcx.fn_sig(callee).abi() == RustIntrinsic; if !tcx.is_const_fn_raw(callee) { - let mut permitted = false; - - let callee_trait = tcx.trait_of_item(callee); - if let Some(trait_id) = callee_trait { - if tcx.has_attr(caller, sym::default_method_body_is_const) { - // permit call to non-const fn when caller has default_method_body_is_const.. - if tcx.trait_of_item(caller) == callee_trait { - // ..and caller and callee are in the same trait. - permitted = true; - } - } - if !permitted { - // if trait's impls are all const, permit the call. - let mut const_impls = true; - tcx.for_each_relevant_impl(trait_id, substs.type_at(0), |imp| { - if const_impls { - if let hir::Constness::NotConst = tcx.impl_constness(imp) { - const_impls = false; - } - } - }); - if const_impls { - permitted = true; - } - } + if tcx.trait_of_item(callee).is_some() { + if tcx.has_attr(callee, sym::default_method_body_is_const) { + // To get to here we must have already found a const impl for the + // trait, but for it to still be non-const can be that the impl is + // using default method bodies. + nonconst_call_permission = true; + } } - if !permitted { + if !nonconst_call_permission { self.check_op(ops::FnCallNonConst); return; } diff --git a/src/test/ui/rfc-2632-const-trait-impl/issue-88155.rs b/src/test/ui/rfc-2632-const-trait-impl/issue-88155.rs new file mode 100644 index 0000000000000..157005bba7b75 --- /dev/null +++ b/src/test/ui/rfc-2632-const-trait-impl/issue-88155.rs @@ -0,0 +1,13 @@ +#![feature(const_fn_trait_bound)] +#![feature(const_trait_impl)] + +pub trait A { + fn assoc() -> bool; +} + +pub const fn foo() -> bool { + T::assoc() + //~^ ERROR calls in constant functions are limited +} + +fn main() {} diff --git a/src/test/ui/rfc-2632-const-trait-impl/issue-88155.stderr b/src/test/ui/rfc-2632-const-trait-impl/issue-88155.stderr new file mode 100644 index 0000000000000..931baac5389e6 --- /dev/null +++ b/src/test/ui/rfc-2632-const-trait-impl/issue-88155.stderr @@ -0,0 +1,9 @@ +error[E0015]: calls in constant functions are limited to constant functions, tuple structs and tuple variants + --> $DIR/issue-88155.rs:9:5 + | +LL | T::assoc() + | ^^^^^^^^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0015`.