diff options
12 files changed, 214 insertions, 68 deletions
diff --git a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs index 43dc68fdb3b..8191dd720e7 100644 --- a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs +++ b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs @@ -10,7 +10,9 @@ use borrow_check::nll::constraints::{OutlivesConstraint}; use borrow_check::nll::region_infer::RegionInferenceContext; +use borrow_check::nll::region_infer::error_reporting::region_name::RegionNameSource; use borrow_check::nll::type_check::Locations; +use borrow_check::nll::universal_regions::DefiningTy; use rustc::hir::def_id::DefId; use rustc::infer::error_reporting::nice_region_error::NiceRegionError; use rustc::infer::InferCtxt; @@ -263,6 +265,9 @@ impl<'tcx> RegionInferenceContext<'tcx> { debug!("report_error: fr_is_local={:?} outlived_fr_is_local={:?} category={:?}", fr_is_local, outlived_fr_is_local, category); match (category, fr_is_local, outlived_fr_is_local) { + (ConstraintCategory::Return, true, false) if self.is_closure_fn_mut(infcx, fr) => + self.report_fnmut_error(mir, infcx, mir_def_id, fr, outlived_fr, span, + errors_buffer), (ConstraintCategory::Assignment, true, false) | (ConstraintCategory::CallArgument, true, false) => self.report_escaping_data_error(mir, infcx, mir_def_id, fr, outlived_fr, @@ -274,6 +279,85 @@ impl<'tcx> RegionInferenceContext<'tcx> { }; } + /// Report a specialized error when `FnMut` closures return a reference to a captured variable. + /// This function expects `fr` to be local and `outlived_fr` to not be local. + /// + /// ```text + /// error: captured variable cannot escape `FnMut` closure body + /// --> $DIR/issue-53040.rs:15:8 + /// | + /// LL | || &mut v; + /// | -- ^^^^^^ creates a reference to a captured variable which escapes the closure body + /// | | + /// | inferred to be a `FnMut` closure + /// | + /// = note: `FnMut` closures only have access to their captured variables while they are + /// executing... + /// = note: ...therefore, returned references to captured variables will escape the closure + /// ``` + fn report_fnmut_error( + &self, + mir: &Mir<'tcx>, + infcx: &InferCtxt<'_, '_, 'tcx>, + mir_def_id: DefId, + _fr: RegionVid, + outlived_fr: RegionVid, + span: Span, + errors_buffer: &mut Vec<Diagnostic>, + ) { + let mut diag = infcx.tcx.sess.struct_span_err( + span, + "captured variable cannot escape `FnMut` closure body", + ); + + // We should check if the return type of this closure is in fact a closure - in that + // case, we can special case the error further. + let return_type_is_closure = self.universal_regions.unnormalized_output_ty.is_closure(); + let message = if return_type_is_closure { + "returns a closure that contains a reference to a captured variable, which then \ + escapes the closure body" + } else { + "returns a reference to a captured variable which escapes the closure body" + }; + + diag.span_label( + span, + message, + ); + + match self.give_region_a_name(infcx, mir, mir_def_id, outlived_fr, &mut 1).source { + RegionNameSource::NamedEarlyBoundRegion(fr_span) | + RegionNameSource::NamedFreeRegion(fr_span) | + RegionNameSource::SynthesizedFreeEnvRegion(fr_span, _) | + RegionNameSource::CannotMatchHirTy(fr_span, _) | + RegionNameSource::MatchedHirTy(fr_span) | + RegionNameSource::MatchedAdtAndSegment(fr_span) | + RegionNameSource::AnonRegionFromUpvar(fr_span, _) | + RegionNameSource::AnonRegionFromOutput(fr_span, _, _) => { + diag.span_label(fr_span, "inferred to be a `FnMut` closure"); + }, + _ => {}, + } + + diag.note("`FnMut` closures only have access to their captured variables while they are \ + executing..."); + diag.note("...therefore, they cannot allow references to captured variables to escape"); + + diag.buffer(errors_buffer); + } + + /// Reports a error specifically for when data is escaping a closure. + /// + /// ```text + /// error: borrowed data escapes outside of function + /// --> $DIR/lifetime-bound-will-change-warning.rs:44:5 + /// | + /// LL | fn test2<'a>(x: &'a Box<Fn()+'a>) { + /// | - `x` is a reference that is only valid in the function body + /// LL | // but ref_obj will not, so warn. + /// LL | ref_obj(x) + /// | ^^^^^^^^^^ `x` escapes the function body here + /// ``` fn report_escaping_data_error( &self, mir: &Mir<'tcx>, @@ -305,31 +389,46 @@ impl<'tcx> RegionInferenceContext<'tcx> { span, &format!("borrowed data escapes outside of {}", escapes_from), ); - if let Some((outlived_fr_name, outlived_fr_span)) = outlived_fr_name_and_span { - if let Some(name) = outlived_fr_name { - diag.span_label( - outlived_fr_span, - format!("`{}` is declared here, outside of the {} body", name, escapes_from), - ); - } + if let Some((Some(outlived_fr_name), outlived_fr_span)) = outlived_fr_name_and_span { + diag.span_label( + outlived_fr_span, + format!( + "`{}` is declared here, outside of the {} body", + outlived_fr_name, escapes_from + ), + ); } - if let Some((fr_name, fr_span)) = fr_name_and_span { - if let Some(name) = fr_name { - diag.span_label( - fr_span, - format!("`{}` is a reference that is only valid in the {} body", - name, escapes_from), - ); + if let Some((Some(fr_name), fr_span)) = fr_name_and_span { + diag.span_label( + fr_span, + format!( + "`{}` is a reference that is only valid in the {} body", + fr_name, escapes_from + ), + ); - diag.span_label(span, format!("`{}` escapes the {} body here", - name, escapes_from)); - } + diag.span_label(span, format!("`{}` escapes the {} body here", fr_name, escapes_from)); } diag.buffer(errors_buffer); } + /// Reports a region inference error for the general case with named/synthesized lifetimes to + /// explain what is happening. + /// + /// ```text + /// error: unsatisfied lifetime constraints + /// --> $DIR/regions-creating-enums3.rs:17:5 + /// | + /// LL | fn mk_add_bad1<'a,'b>(x: &'a ast<'a>, y: &'b ast<'b>) -> ast<'a> { + /// | -- -- lifetime `'b` defined here + /// | | + /// | lifetime `'a` defined here + /// LL | ast::add(x, y) + /// | ^^^^^^^^^^^^^^ function was supposed to return data with lifetime `'a` but it + /// | is returning data with lifetime `'b` + /// ``` fn report_general_error( &self, mir: &Mir<'tcx>, @@ -380,6 +479,15 @@ impl<'tcx> RegionInferenceContext<'tcx> { diag.buffer(errors_buffer); } + /// Adds a suggestion to errors where a `impl Trait` is returned. + /// + /// ```text + /// help: to allow this impl Trait to capture borrowed data with lifetime `'1`, add `'_` as + /// a constraint + /// | + /// LL | fn iter_values_anon(&self) -> impl Iterator<Item=u32> + 'a { + /// | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + /// ``` fn add_static_impl_trait_suggestion( &self, infcx: &InferCtxt<'_, '_, 'tcx>, @@ -500,4 +608,22 @@ impl<'tcx> RegionInferenceContext<'tcx> { .get(&(constraint.sup, constraint.sub)); *opt_span_category.unwrap_or(&(constraint.category, mir.source_info(loc).span)) } + + /// Returns `true` if a closure is inferred to be an `FnMut` closure. + crate fn is_closure_fn_mut( + &self, + infcx: &InferCtxt<'_, '_, 'tcx>, + fr: RegionVid, + ) -> bool { + if let Some(ty::ReFree(free_region)) = self.to_error_region(fr) { + if let ty::BoundRegion::BrEnv = free_region.bound_region { + if let DefiningTy::Closure(def_id, substs) = self.universal_regions.defining_ty { + let closure_kind_ty = substs.closure_kind_ty(def_id, infcx.tcx); + return Some(ty::ClosureKind::FnMut) == closure_kind_ty.to_opt_closure_kind(); + } + } + } + + false + } } diff --git a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs index 3a545d9adbf..65ba2f537bf 100644 --- a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs +++ b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs @@ -27,8 +27,8 @@ use syntax_pos::symbol::InternedString; #[derive(Debug)] crate struct RegionName { - name: InternedString, - source: RegionNameSource, + crate name: InternedString, + crate source: RegionNameSource, } #[derive(Debug)] diff --git a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/var_name.rs b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/var_name.rs index 57ff0f4c10a..73fa1b0cfb7 100644 --- a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/var_name.rs +++ b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/var_name.rs @@ -50,11 +50,12 @@ impl<'tcx> RegionInferenceContext<'tcx> { .defining_ty .upvar_tys(tcx) .position(|upvar_ty| { - debug!( - "get_upvar_index_for_region: upvar_ty = {:?}", - upvar_ty, - ); - tcx.any_free_region_meets(&upvar_ty, |r| r.to_region_vid() == fr) + debug!("get_upvar_index_for_region: upvar_ty={:?}", upvar_ty); + tcx.any_free_region_meets(&upvar_ty, |r| { + let r = r.to_region_vid(); + debug!("get_upvar_index_for_region: r={:?} fr={:?}", r, fr); + r == fr + }) })?; let upvar_ty = self diff --git a/src/test/ui/borrowck/borrowck-describe-lvalue.ast.nll.stderr b/src/test/ui/borrowck/borrowck-describe-lvalue.ast.nll.stderr index ac6cfac2a16..5721c52ba21 100644 --- a/src/test/ui/borrowck/borrowck-describe-lvalue.ast.nll.stderr +++ b/src/test/ui/borrowck/borrowck-describe-lvalue.ast.nll.stderr @@ -20,24 +20,22 @@ LL | //[mir]~^ ERROR cannot borrow `x` as mutable more than o LL | *y = 1; | ------ first borrow later used here -error: unsatisfied lifetime constraints +error: captured variable cannot escape `FnMut` closure body --> $DIR/borrowck-describe-lvalue.rs:305:16 | LL | || { - | -- - | || - | |return type of closure is [closure@$DIR/borrowck-describe-lvalue.rs:305:16: 311:18 x:&'2 mut i32] - | lifetime `'1` represents this closure's body -LL | / || { //[mir]~ ERROR unsatisfied lifetime constraints + | - inferred to be a `FnMut` closure +LL | / || { //[mir]~ ERROR captured variable cannot escape `FnMut` closure body LL | | let y = &mut x; LL | | &mut x; //[ast]~ ERROR cannot borrow `**x` as mutable more than once at a time LL | | //[mir]~^ ERROR cannot borrow `x` as mutable more than once at a time LL | | *y = 1; LL | | drop(y); LL | | } - | |_________________^ returning this value requires that `'1` must outlive `'2` + | |_________________^ returns a closure that contains a reference to a captured variable, which then escapes the closure body | - = note: closure implements `FnMut`, so references to captured variables can't escape the closure + = note: `FnMut` closures only have access to their captured variables while they are executing... + = note: ...therefore, they cannot allow references to captured variables to escape error[E0503]: cannot use `f.x` because it was mutably borrowed --> $DIR/borrowck-describe-lvalue.rs:53:9 diff --git a/src/test/ui/borrowck/borrowck-describe-lvalue.mir.stderr b/src/test/ui/borrowck/borrowck-describe-lvalue.mir.stderr index ac6cfac2a16..5721c52ba21 100644 --- a/src/test/ui/borrowck/borrowck-describe-lvalue.mir.stderr +++ b/src/test/ui/borrowck/borrowck-describe-lvalue.mir.stderr @@ -20,24 +20,22 @@ LL | //[mir]~^ ERROR cannot borrow `x` as mutable more than o LL | *y = 1; | ------ first borrow later used here -error: unsatisfied lifetime constraints +error: captured variable cannot escape `FnMut` closure body --> $DIR/borrowck-describe-lvalue.rs:305:16 | LL | || { - | -- - | || - | |return type of closure is [closure@$DIR/borrowck-describe-lvalue.rs:305:16: 311:18 x:&'2 mut i32] - | lifetime `'1` represents this closure's body -LL | / || { //[mir]~ ERROR unsatisfied lifetime constraints + | - inferred to be a `FnMut` closure +LL | / || { //[mir]~ ERROR captured variable cannot escape `FnMut` closure body LL | | let y = &mut x; LL | | &mut x; //[ast]~ ERROR cannot borrow `**x` as mutable more than once at a time LL | | //[mir]~^ ERROR cannot borrow `x` as mutable more than once at a time LL | | *y = 1; LL | | drop(y); LL | | } - | |_________________^ returning this value requires that `'1` must outlive `'2` + | |_________________^ returns a closure that contains a reference to a captured variable, which then escapes the closure body | - = note: closure implements `FnMut`, so references to captured variables can't escape the closure + = note: `FnMut` closures only have access to their captured variables while they are executing... + = note: ...therefore, they cannot allow references to captured variables to escape error[E0503]: cannot use `f.x` because it was mutably borrowed --> $DIR/borrowck-describe-lvalue.rs:53:9 diff --git a/src/test/ui/borrowck/borrowck-describe-lvalue.rs b/src/test/ui/borrowck/borrowck-describe-lvalue.rs index 2ef08e75cfd..649de888ab0 100644 --- a/src/test/ui/borrowck/borrowck-describe-lvalue.rs +++ b/src/test/ui/borrowck/borrowck-describe-lvalue.rs @@ -302,7 +302,7 @@ fn main() { // FIXME(#49824) -- the free region error below should probably not be there let mut x = 0; || { - || { //[mir]~ ERROR unsatisfied lifetime constraints + || { //[mir]~ ERROR captured variable cannot escape `FnMut` closure body let y = &mut x; &mut x; //[ast]~ ERROR cannot borrow `**x` as mutable more than once at a time //[mir]~^ ERROR cannot borrow `x` as mutable more than once at a time diff --git a/src/test/ui/issues/issue-40510-1.nll.stderr b/src/test/ui/issues/issue-40510-1.nll.stderr index 3a579c04de1..1aeb1a89ead 100644 --- a/src/test/ui/issues/issue-40510-1.nll.stderr +++ b/src/test/ui/issues/issue-40510-1.nll.stderr @@ -1,15 +1,13 @@ -error: unsatisfied lifetime constraints +error: captured variable cannot escape `FnMut` closure body --> $DIR/issue-40510-1.rs:18:9 | LL | || { - | -- - | || - | |return type of closure is &'2 mut std::boxed::Box<()> - | lifetime `'1` represents this closure's body + | - inferred to be a `FnMut` closure LL | &mut x - | ^^^^^^ returning this value requires that `'1` must outlive `'2` + | ^^^^^^ returns a reference to a captured variable which escapes the closure body | - = note: closure implements `FnMut`, so references to captured variables can't escape the closure + = note: `FnMut` closures only have access to their captured variables while they are executing... + = note: ...therefore, they cannot allow references to captured variables to escape error: aborting due to previous error diff --git a/src/test/ui/issues/issue-40510-3.nll.stderr b/src/test/ui/issues/issue-40510-3.nll.stderr index 84ab2a8216d..c334e592fbc 100644 --- a/src/test/ui/issues/issue-40510-3.nll.stderr +++ b/src/test/ui/issues/issue-40510-3.nll.stderr @@ -1,17 +1,15 @@ -error: unsatisfied lifetime constraints +error: captured variable cannot escape `FnMut` closure body --> $DIR/issue-40510-3.rs:18:9 | LL | || { - | -- - | || - | |return type of closure is [closure@$DIR/issue-40510-3.rs:18:9: 20:10 x:&'2 mut std::vec::Vec<()>] - | lifetime `'1` represents this closure's body + | - inferred to be a `FnMut` closure LL | / || { LL | | x.push(()) LL | | } - | |_________^ returning this value requires that `'1` must outlive `'2` + | |_________^ returns a closure that contains a reference to a captured variable, which then escapes the closure body | - = note: closure implements `FnMut`, so references to captured variables can't escape the closure + = note: `FnMut` closures only have access to their captured variables while they are executing... + = note: ...therefore, they cannot allow references to captured variables to escape error: aborting due to previous error diff --git a/src/test/ui/issues/issue-49824.nll.stderr b/src/test/ui/issues/issue-49824.nll.stderr index df43158ec9c..2e0463fdd1d 100644 --- a/src/test/ui/issues/issue-49824.nll.stderr +++ b/src/test/ui/issues/issue-49824.nll.stderr @@ -1,17 +1,15 @@ -error: unsatisfied lifetime constraints +error: captured variable cannot escape `FnMut` closure body --> $DIR/issue-49824.rs:22:9 | LL | || { - | -- - | || - | |return type of closure is [closure@$DIR/issue-49824.rs:22:9: 24:10 x:&'2 mut i32] - | lifetime `'1` represents this closure's body + | - inferred to be a `FnMut` closure LL | / || { LL | | let _y = &mut x; LL | | } - | |_________^ returning this value requires that `'1` must outlive `'2` + | |_________^ returns a closure that contains a reference to a captured variable, which then escapes the closure body | - = note: closure implements `FnMut`, so references to captured variables can't escape the closure + = note: `FnMut` closures only have access to their captured variables while they are executing... + = note: ...therefore, they cannot allow references to captured variables to escape error: aborting due to previous error diff --git a/src/test/ui/nll/issue-53040.rs b/src/test/ui/nll/issue-53040.rs new file mode 100644 index 00000000000..2b6e67be6d9 --- /dev/null +++ b/src/test/ui/nll/issue-53040.rs @@ -0,0 +1,16 @@ +// Copyright 2017 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 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +#![feature(nll)] + +fn main() { + let mut v: Vec<()> = Vec::new(); + || &mut v; +} diff --git a/src/test/ui/nll/issue-53040.stderr b/src/test/ui/nll/issue-53040.stderr new file mode 100644 index 00000000000..fac9969f193 --- /dev/null +++ b/src/test/ui/nll/issue-53040.stderr @@ -0,0 +1,13 @@ +error: captured variable cannot escape `FnMut` closure body + --> $DIR/issue-53040.rs:15:8 + | +LL | || &mut v; + | - ^^^^^^ returns a reference to a captured variable which escapes the closure body + | | + | inferred to be a `FnMut` closure + | + = note: `FnMut` closures only have access to their captured variables while they are executing... + = note: ...therefore, they cannot allow references to captured variables to escape + +error: aborting due to previous error + diff --git a/src/test/ui/regions/regions-return-ref-to-upvar-issue-17403.nll.stderr b/src/test/ui/regions/regions-return-ref-to-upvar-issue-17403.nll.stderr index 35c1da61ae2..300a5639822 100644 --- a/src/test/ui/regions/regions-return-ref-to-upvar-issue-17403.nll.stderr +++ b/src/test/ui/regions/regions-return-ref-to-upvar-issue-17403.nll.stderr @@ -1,13 +1,13 @@ -error: unsatisfied lifetime constraints +error: captured variable cannot escape `FnMut` closure body --> $DIR/regions-return-ref-to-upvar-issue-17403.rs:17:24 | LL | let mut f = || &mut x; //~ ERROR cannot infer - | -- ^^^^^^ returning this value requires that `'1` must outlive `'2` - | || - | |return type of closure is &'2 mut i32 - | lifetime `'1` represents this closure's body + | - ^^^^^^ returns a reference to a captured variable which escapes the closure body + | | + | inferred to be a `FnMut` closure | - = note: closure implements `FnMut`, so references to captured variables can't escape the closure + = note: `FnMut` closures only have access to their captured variables while they are executing... + = note: ...therefore, they cannot allow references to captured variables to escape error: aborting due to previous error |