Fix ICE in region naming.

This commit puts a fix in place for the ICE in region naming code so
that it doesn't break the compiler. However, this results in the
diagnostic being poorer as the borrow explanation that was causing the
ICE is not being added - this should be fixed as a follow-up.

diff --git a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs
index 477b78926084e86d0efa701f2b66ba47519bbca3..7fb3f02e0e3f3f07c3367bd61ab647d6a908d9ad 100644 (file)
--- a/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs
@@ -277,13 +277,17 @@ pub(in borrow_check) fn explain_why_borrow_contains_point(
                         borrow_region_vid,
                         region,
                     );
-                let opt_place_desc = self.describe_place(&borrow.borrowed_place);
-                BorrowExplanation::MustBeValidFor {
-                    category,
-                    from_closure,
-                    span,
-                    region_name,
-                    opt_place_desc,
+                if let Some(region_name) = region_name {
+                    let opt_place_desc = self.describe_place(&borrow.borrowed_place);
+                    BorrowExplanation::MustBeValidFor {
+                        category,
+                        from_closure,
+                        span,
+                        region_name,
+                        opt_place_desc,
+                    }
+                } else {
+                    BorrowExplanation::Unexplained
                 }
             } else {
                 BorrowExplanation::Unexplained

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 940f9d6040cf522b825df6f67e682e6d4ac96afc..32aaa0590d2f9efbe6d3df17e8d52086c9aed831 100644 (file)
--- 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
@@ -376,9 +376,7 @@ fn report_fnmut_error(
 
         diag.span_label(span, message);
 
-        match self.give_region_a_name(infcx, mir, mir_def_id, outlived_fr, &mut 1)
-            .source
-        {
+        match self.give_region_a_name(infcx, mir, mir_def_id, outlived_fr, &mut 1).unwrap().source {
             RegionNameSource::NamedEarlyBoundRegion(fr_span)
             | RegionNameSource::NamedFreeRegion(fr_span)
             | RegionNameSource::SynthesizedFreeEnvRegion(fr_span, _)
@@ -521,10 +519,10 @@ fn report_general_error(
         );
 
         let counter = &mut 1;
-        let fr_name = self.give_region_a_name(infcx, mir, mir_def_id, fr, counter);
+        let fr_name = self.give_region_a_name(infcx, mir, mir_def_id, fr, counter).unwrap();
         fr_name.highlight_region_name(&mut diag);
         let outlived_fr_name =
-            self.give_region_a_name(infcx, mir, mir_def_id, outlived_fr, counter);
+            self.give_region_a_name(infcx, mir, mir_def_id, outlived_fr, counter).unwrap();
         outlived_fr_name.highlight_region_name(&mut diag);
 
         let mir_def_name = if infcx.tcx.is_closure(mir_def_id) {
@@ -661,7 +659,7 @@ fn add_static_impl_trait_suggestion(
         infcx: &InferCtxt<'_, '_, 'tcx>,
         borrow_region: RegionVid,
         outlived_region: RegionVid,
-    ) -> (ConstraintCategory, bool, Span, RegionName) {
+    ) -> (ConstraintCategory, bool, Span, Option<RegionName>) {
         let (category, from_closure, span) =
             self.best_blame_constraint(mir, borrow_region, |r| r == outlived_region);
         let outlived_fr_name =

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 a32fb0503a814e6ba74f7e65f3134091de8eded8..b01e257ae2effd5ac7f2b506d3e24a0f6fd8695a 100644 (file)
--- 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
@@ -157,7 +157,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         mir_def_id: DefId,
         fr: RegionVid,
         counter: &mut usize,
-    ) -> RegionName {
+    ) -> Option<RegionName> {
         debug!("give_region_a_name(fr={:?}, counter={})", fr, counter);
 
         assert!(self.universal_regions.is_universal_region(fr));
@@ -177,8 +177,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 self.give_name_if_anonymous_region_appears_in_output(
                     infcx, mir, mir_def_id, fr, counter,
                 )
-            })
-            .unwrap_or_else(|| span_bug!(mir.span, "can't make a name for free region {:?}", fr));
+            });
 
         debug!("give_region_a_name: gave name {:?}", value);
         value

diff --git a/src/test/ui/nll/issue-55850.nll.stderr b/src/test/ui/nll/issue-55850.nll.stderr
new file mode 100644 (file)
index 0000000..08e5217
--- /dev/null
+++ b/src/test/ui/nll/issue-55850.nll.stderr
@@ -0,0 +1,18 @@
+error[E0597]: `s` does not live long enough
+  --> $DIR/issue-55850.rs:38:16
+   |
+LL |         yield &s[..] //~ ERROR `s` does not live long enough [E0597]
+   |                ^ borrowed value does not live long enough
+LL |     })
+   |     - `s` dropped here while still borrowed
+
+error[E0626]: borrow may still be in use when generator yields
+  --> $DIR/issue-55850.rs:38:16
+   |
+LL |         yield &s[..] //~ ERROR `s` does not live long enough [E0597]
+   |         -------^---- possible yield occurs here
+
+error: aborting due to 2 previous errors
+
+Some errors occurred: E0597, E0626.
+For more information about an error, try `rustc --explain E0597`.

diff --git a/src/test/ui/nll/issue-55850.rs b/src/test/ui/nll/issue-55850.rs
new file mode 100644 (file)
index 0000000..4140815
--- /dev/null
+++ b/src/test/ui/nll/issue-55850.rs
@@ -0,0 +1,44 @@
+// 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 <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.
+
+#![allow(unused_mut)]
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+use std::ops::GeneratorState::Yielded;
+
+pub struct GenIter<G>(G);
+
+impl <G> Iterator for GenIter<G>
+where
+    G: Generator,
+{
+    type Item = G::Yield;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        unsafe {
+            match self.0.resume() {
+                Yielded(y) => Some(y),
+                _ => None
+            }
+        }
+    }
+}
+
+fn bug<'a>() -> impl Iterator<Item = &'a str> {
+    GenIter(move || {
+        let mut s = String::new();
+        yield &s[..] //~ ERROR `s` does not live long enough [E0597]
+    })
+}
+
+fn main() {
+    bug();
+}

diff --git a/src/test/ui/nll/issue-55850.stderr b/src/test/ui/nll/issue-55850.stderr
new file mode 100644 (file)
index 0000000..26b4c82
--- /dev/null
+++ b/src/test/ui/nll/issue-55850.stderr
@@ -0,0 +1,17 @@
+error[E0597]: `s` does not live long enough
+  --> $DIR/issue-55850.rs:38:16
+   |
+LL |         yield &s[..] //~ ERROR `s` does not live long enough [E0597]
+   |                ^ borrowed value does not live long enough
+LL |     })
+   |     - borrowed value only lives until here
+   |
+note: borrowed value must be valid for the lifetime 'a as defined on the function body at 35:8...
+  --> $DIR/issue-55850.rs:35:8
+   |
+LL | fn bug<'a>() -> impl Iterator<Item = &'a str> {
+   |        ^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.