Rollup merge of #52617 - matthewjasper:remove-unused-code, r=nikomatsakis

Don't match on region kinds when reporting NLL errors

First half (by number of tests affected) of the changes to "does not live long enough".

Now that lexical MIR borrowck is gone, region kinds are always ReVar, so matching on them to change errors does nothing.

Changes "borrowed value only lives until here" to "`x` is dropped here while still borrowed".

r? @pnkfelix  cc @nikomatsakis

Author: Mark-Simulacrum

src/librustc_mir/borrow_check/error_reporting.rs

@@ -14,7 +14,7 @@ use rustc::mir::{BindingForm, BorrowKind, ClearCrossCrate, Field, Local};
 use rustc::mir::{LocalDecl, LocalKind, Location, Operand, Place};
 use rustc::mir::{ProjectionElem, Rvalue, Statement, StatementKind};
 use rustc::mir::VarBindingForm;
-use rustc::ty::{self, RegionKind};
+use rustc::ty;
 use rustc_data_structures::indexed_vec::Idx;
 use rustc_data_structures::sync::Lrc;
 use syntax_pos::Span;
@@ -427,34 +427,9 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         self.access_place_error_reported
             .insert((root_place.clone(), borrow_span));
 
-        match (borrow.region, &self.describe_place(&borrow.borrowed_place)) {
-            (RegionKind::ReScope(_), Some(name)) => {
-                self.report_scoped_local_value_does_not_live_long_enough(
-                    context,
-                    name,
-                    &scope_tree,
-                    &borrow,
-                    drop_span,
-                    borrow_span,
-                    proper_span,
-                );
-            }
-            (RegionKind::ReScope(_), None) => {
-                self.report_scoped_temporary_value_does_not_live_long_enough(
-                    context,
-                    &scope_tree,
-                    &borrow,
-                    drop_span,
-                    borrow_span,
-                    proper_span,
-                );
-            }
-            (RegionKind::ReEarlyBound(_), Some(name))
-            | (RegionKind::ReFree(_), Some(name))
-            | (RegionKind::ReStatic, Some(name))
-            | (RegionKind::ReEmpty, Some(name))
-            | (RegionKind::ReVar(_), Some(name)) => {
-                self.report_unscoped_local_value_does_not_live_long_enough(
+        match &self.describe_place(&borrow.borrowed_place) {
+            Some(name) => {
+                self.report_local_value_does_not_live_long_enough(
                     context,
                     name,
                     &scope_tree,
@@ -465,12 +440,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                     kind.map(|k| (k, place_span.0)),
                 );
             }
-            (RegionKind::ReEarlyBound(_), None)
-            | (RegionKind::ReFree(_), None)
-            | (RegionKind::ReStatic, None)
-            | (RegionKind::ReEmpty, None)
-            | (RegionKind::ReVar(_), None) => {
-                self.report_unscoped_temporary_value_does_not_live_long_enough(
+            None => {
+                self.report_temporary_value_does_not_live_long_enough(
                     context,
                     &scope_tree,
                     &borrow,
@@ -479,65 +450,10 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                     proper_span,
                 );
             }
-            (RegionKind::ReLateBound(_, _), _)
-            | (RegionKind::ReSkolemized(_, _), _)
-            | (RegionKind::ReClosureBound(_), _)
-            | (RegionKind::ReCanonical(_), _)
-            | (RegionKind::ReErased, _) => {
-                span_bug!(
-                    drop_span,
-                    "region {:?} does not make sense in this context",
-                    borrow.region
-                );
-            }
         }
     }
 
-    fn report_scoped_local_value_does_not_live_long_enough(
-        &mut self,
-        context: Context,
-        name: &String,
-        _scope_tree: &Lrc<ScopeTree>,
-        borrow: &BorrowData<'tcx>,
-        drop_span: Span,
-        borrow_span: Span,
-        _proper_span: Span,
-    ) {
-        let tcx = self.tcx;
-        let mut err =
-            tcx.path_does_not_live_long_enough(borrow_span, &format!("`{}`", name), Origin::Mir);
-        err.span_label(borrow_span, "borrowed value does not live long enough");
-        err.span_label(
-            drop_span,
-            format!("`{}` dropped here while still borrowed", name),
-        );
-        self.explain_why_borrow_contains_point(context, borrow, None, &mut err);
-        err.buffer(&mut self.errors_buffer);
-    }
-
-    fn report_scoped_temporary_value_does_not_live_long_enough(
-        &mut self,
-        context: Context,
-        _scope_tree: &Lrc<ScopeTree>,
-        borrow: &BorrowData<'tcx>,
-        drop_span: Span,
-        _borrow_span: Span,
-        proper_span: Span,
-    ) {
-        let tcx = self.tcx;
-        let mut err =
-            tcx.path_does_not_live_long_enough(proper_span, "borrowed value", Origin::Mir);
-        err.span_label(proper_span, "temporary value does not live long enough");
-        err.span_label(
-            drop_span,
-            "temporary value dropped here while still borrowed",
-        );
-        err.note("consider using a `let` binding to increase its lifetime");
-        self.explain_why_borrow_contains_point(context, borrow, None, &mut err);
-        err.buffer(&mut self.errors_buffer);
-    }
-
-    fn report_unscoped_local_value_does_not_live_long_enough(
+    fn report_local_value_does_not_live_long_enough(
         &mut self,
         context: Context,
         name: &String,
@@ -549,7 +465,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         kind_place: Option<(WriteKind, &Place<'tcx>)>,
     ) {
         debug!(
-            "report_unscoped_local_value_does_not_live_long_enough(\
+            "report_local_value_does_not_live_long_enough(\
              {:?}, {:?}, {:?}, {:?}, {:?}, {:?}\
              )",
             context, name, scope_tree, borrow, drop_span, borrow_span
@@ -559,13 +475,16 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         let mut err =
             tcx.path_does_not_live_long_enough(borrow_span, &format!("`{}`", name), Origin::Mir);
         err.span_label(borrow_span, "borrowed value does not live long enough");
-        err.span_label(drop_span, "borrowed value only lives until here");
+        err.span_label(
+            drop_span,
+            format!("`{}` dropped here while still borrowed", name),
+        );
 
         self.explain_why_borrow_contains_point(context, borrow, kind_place, &mut err);
         err.buffer(&mut self.errors_buffer);
     }
 
-    fn report_unscoped_temporary_value_does_not_live_long_enough(
+    fn report_temporary_value_does_not_live_long_enough(
         &mut self,
         context: Context,
         scope_tree: &Lrc<ScopeTree>,
@@ -575,7 +494,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         proper_span: Span,
     ) {
         debug!(
-            "report_unscoped_temporary_value_does_not_live_long_enough(\
+            "report_temporary_value_does_not_live_long_enough(\
              {:?}, {:?}, {:?}, {:?}, {:?}\
              )",
             context, scope_tree, borrow, drop_span, proper_span

src/test/ui/borrowck/borrowck-escaping-closure-error-1.nll.stderr

@@ -5,7 +5,7 @@ LL |     spawn(|| books.push(4));
    |           ^^^^^^^^^^^^^^^^ borrowed value does not live long enough
 LL |     //~^ ERROR E0373
 LL | }
-   | - borrowed value only lives until here
+   | - `books` dropped here while still borrowed
    |
    = note: borrowed value must be valid for the static lifetime...
 

src/test/ui/borrowck/borrowck-escaping-closure-error-2.nll.stderr

@@ -5,7 +5,7 @@ LL |     Box::new(|| books.push(4))
    |              ^^^^^^^^^^^^^^^^ borrowed value does not live long enough
 LL |     //~^ ERROR E0373
 LL | }
-   | - borrowed value only lives until here
+   | - `books` dropped here while still borrowed
    |
 note: borrowed value must be valid for the lifetime 'a as defined on the function body at 19:8...
   --> $DIR/borrowck-escaping-closure-error-2.rs:19:8

src/test/ui/dropck/dropck-eyepatch-extern-crate.nll.stderr

@@ -7,7 +7,7 @@ LL |     dt = Dt("dt", &c_shortest);
 LL | }
    | -
    | |
-   | borrowed value only lives until here
+   | `c_shortest` dropped here while still borrowed
    | borrow later used here, when `dt` is dropped
    |
    = note: values in a scope are dropped in the opposite order they are defined

src/test/ui/dropck/dropck-eyepatch-reorder.nll.stderr

@@ -7,7 +7,7 @@ LL |     dt = Dt("dt", &c_shortest);
 LL | }
    | -
    | |
-   | borrowed value only lives until here
+   | `c_shortest` dropped here while still borrowed
    | borrow later used here, when `dt` is dropped
    |
    = note: values in a scope are dropped in the opposite order they are defined

src/test/ui/dropck/dropck-eyepatch.nll.stderr

@@ -7,7 +7,7 @@ LL |     dt = Dt("dt", &c_shortest);
 LL | }
    | -
    | |
-   | borrowed value only lives until here
+   | `c_shortest` dropped here while still borrowed
    | borrow later used here, when `dt` is dropped
    |
    = note: values in a scope are dropped in the opposite order they are defined

src/test/ui/error-codes/E0597.nll.stderr

@@ -7,7 +7,7 @@ LL |     //~^ `y` does not live long enough [E0597]
 LL | }
    | -
    | |
-   | borrowed value only lives until here
+   | `y` dropped here while still borrowed
    | borrow later used here, when `x` is dropped
    |
    = note: values in a scope are dropped in the opposite order they are defined

src/test/ui/generator/borrowing.nll.stderr

@@ -5,7 +5,7 @@ LL |         unsafe { (|| yield &a).resume() }
    |                  ^^^^^^^^^^^^^ borrowed value does not live long enough
 LL |         //~^ ERROR: `a` does not live long enough
 LL |     };
-   |     - borrowed value only lives until here
+   |     - `a` dropped here while still borrowed
 
 error[E0597]: `a` does not live long enough
   --> $DIR/borrowing.rs:24:9
@@ -16,7 +16,7 @@ LL | |             //~^ ERROR: `a` does not live long enough
 LL | |         }
    | |_________^ borrowed value does not live long enough
 LL |       };
-   |       - borrowed value only lives until here
+   |       - `a` dropped here while still borrowed
 LL |   }
    |   - borrow later used here, when `_b` is dropped
 

src/test/ui/generator/dropck.nll.stderr

@@ -7,7 +7,7 @@ LL |     let ref_ = Box::leak(Box::new(Some(cell.borrow_mut())));
 LL | }
    | -
    | |
-   | borrowed value only lives until here
+   | `*cell` dropped here while still borrowed
    | borrow later used here, when `gen` is dropped
    |
    = note: values in a scope are dropped in the opposite order they are defined
@@ -26,7 +26,7 @@ LL | |     };
 LL |   }
    |   -
    |   |
-   |   borrowed value only lives until here
+   |   `ref_` dropped here while still borrowed
    |   borrow later used here, when `gen` is dropped
    |
    = note: values in a scope are dropped in the opposite order they are defined

src/test/ui/generator/ref-escapes-but-not-over-yield.nll.stderr

@@ -5,7 +5,7 @@ LL |         a = &b;
    |             ^^ borrowed value does not live long enough
 LL |         //~^ ERROR `b` does not live long enough
 LL |     };
-   |     - borrowed value only lives until here
+   |     - `b` dropped here while still borrowed
 
 error: aborting due to previous error