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;
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,
};
}
+ /// 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",
+ );
+
+ diag.span_label(
+ span,
+ "creates a reference to a captured variable which escapes the closure body",
+ );
+
+ 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>,
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>,
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>,
.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
+ }
}
projects / rust.git / commitdiff