diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs index 54ac04bea9c4c..4eda1ed23b757 100644 --- a/src/librustc_mir/transform/qualify_consts.rs +++ b/src/librustc_mir/transform/qualify_consts.rs @@ -64,13 +64,18 @@ bitflags! { // pointer comparisons, ptr-to-int casts, etc. const NOT_CONST = 1 << 6, + // Refers to temporaries which cannot be promoted as + // promote_consts decided they weren't simple enough. + const NOT_PROMOTABLE = 1 << 7, + // Borrows of temporaries can be promoted only // if they have none of the above qualifications. - const UNPROMOTABLE = !0, + const NEVER_PROMOTE = !0, // Const items can only have MUTABLE_INTERIOR - // without producing an error. - const CONST_ERROR = !Qualif::MUTABLE_INTERIOR.bits + // and NOT_PROMOTABLE without producing an error. + const CONST_ERROR = !Qualif::MUTABLE_INTERIOR.bits & + !Qualif::NOT_PROMOTABLE.bits } } @@ -503,6 +508,10 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> { self.add(Qualif::NOT_CONST); } Lvalue::Temp(index) => { + if !self.temp_promotion_state[index as usize].is_promotable() { + self.add(Qualif::NOT_PROMOTABLE); + } + if let Some(qualif) = self.temp_qualif[index as usize] { self.add(qualif); } else { @@ -688,8 +697,11 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> { // We might have a candidate for promotion. let candidate = Candidate::Ref(self.location); if self.mode == Mode::Fn || self.mode == Mode::ConstFn { - if !self.qualif.intersects(Qualif::UNPROMOTABLE) { - self.promotion_candidates.push(candidate); + if !self.qualif.intersects(Qualif::NEVER_PROMOTE) { + // We can only promote direct borrows of temps. + if let Lvalue::Temp(_) = *lvalue { + self.promotion_candidates.push(candidate); + } } } } @@ -781,7 +793,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> { this.visit_operand(arg); if is_shuffle && i == 2 && this.mode == Mode::Fn { let candidate = Candidate::ShuffleIndices(bb); - if !this.qualif.intersects(Qualif::UNPROMOTABLE) { + if !this.qualif.intersects(Qualif::NEVER_PROMOTE) { this.promotion_candidates.push(candidate); } else { span_err!(this.tcx.sess, this.span, E0526, diff --git a/src/test/run-pass/issue-33537.rs b/src/test/run-pass/issue-33537.rs new file mode 100644 index 0000000000000..24f4c9f590b11 --- /dev/null +++ b/src/test/run-pass/issue-33537.rs @@ -0,0 +1,24 @@ +// Copyright 2016 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +#![feature(const_fn)] + +const fn foo() -> *const i8 { + b"foo" as *const _ as *const i8 +} + +const fn bar() -> i32 { + *&{(1, 2, 3).1} +} + +fn main() { + assert_eq!(foo(), b"foo" as *const _ as *const i8); + assert_eq!(bar(), 2); +}