Auto merge of #53865 - zilbuz:issue-52768, r=pnkfelix

Remove 'not reporting regions error due to nll' warning

Fix #52768

Author: bors

src/librustc/infer/error_reporting/mod.rs

@@ -68,6 +68,7 @@ use middle::region;
 use traits::{ObligationCause, ObligationCauseCode};
 use ty::{self, subst::Subst, Region, Ty, TyCtxt, TypeFoldable, TyKind};
 use ty::error::TypeError;
+use session::config::BorrowckMode;
 use syntax::ast::DUMMY_NODE_ID;
 use syntax_pos::{Pos, Span};
 use errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
@@ -303,40 +304,16 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     ) {
         debug!("report_region_errors(): {} errors to start", errors.len());
 
-        if will_later_be_reported_by_nll &&
-            // FIXME: `use_mir_borrowck` seems wrong here...
-            self.tcx.use_mir_borrowck() &&
-            // ... this is a band-aid; may be better to explicitly
-            // match on every borrowck_mode variant to guide decision
-            // here.
-            !self.tcx.migrate_borrowck() {
-
-            // With `#![feature(nll)]`, we want to present a nice user
-            // experience, so don't even mention the errors from the
-            // AST checker.
-            if self.tcx.features().nll {
-                return;
+        // If the errors will later be reported by NLL, choose wether to display them or not based
+        // on the borrowck mode
+        if will_later_be_reported_by_nll {
+            match self.tcx.borrowck_mode() {
+                // If we're on AST or Migrate mode, report AST region errors
+                BorrowckMode::Ast | BorrowckMode::Migrate => {},
+                // If we're on MIR or Compare mode, don't report AST region errors as they should
+                // be reported by NLL
+                BorrowckMode::Compare | BorrowckMode::Mir => return,
             }
-
-            // But with nll, it's nice to have some note for later.
-            for error in errors {
-                match *error {
-                    RegionResolutionError::ConcreteFailure(ref origin, ..)
-                    | RegionResolutionError::GenericBoundFailure(ref origin, ..) => {
-                        self.tcx
-                            .sess
-                            .span_warn(origin.span(), "not reporting region error due to nll");
-                    }
-
-                    RegionResolutionError::SubSupConflict(ref rvo, ..) => {
-                        self.tcx
-                            .sess
-                            .span_warn(rvo.span(), "not reporting region error due to nll");
-                    }
-                }
-            }
-
-            return;
         }
 
         // try to pre-process the errors, which will group some of them

src/test/ui/associated-types/associated-types-project-from-hrtb-in-fn-body.nll.stderr

@@ -1,9 +1,3 @@
-warning: not reporting region error due to nll
-  --> $DIR/associated-types-project-from-hrtb-in-fn-body.rs:32:12
-   |
-LL |     let z: I::A = if cond { x } else { y };
-   |            ^^^^
-
 error: unsatisfied lifetime constraints
   --> $DIR/associated-types-project-from-hrtb-in-fn-body.rs:32:29
    |

src/test/ui/associated-types/cache/project-fn-ret-contravariant.krisskross.nll.stderr

@@ -1,15 +1,3 @@
-warning: not reporting region error due to nll
-  --> $DIR/project-fn-ret-contravariant.rs:53:16
-   |
-LL |    let a = bar(foo, y);
-   |                ^^^
-
-warning: not reporting region error due to nll
-  --> $DIR/project-fn-ret-contravariant.rs:54:16
-   |
-LL |    let b = bar(foo, x);
-   |                ^^^
-
 error: unsatisfied lifetime constraints
   --> $DIR/project-fn-ret-contravariant.rs:53:12
    |

src/test/ui/associated-types/cache/project-fn-ret-contravariant.transmute.nll.stderr

@@ -1,9 +1,3 @@
-warning: not reporting region error due to nll
-  --> $DIR/project-fn-ret-contravariant.rs:48:8
-   |
-LL |    bar(foo, x) //[transmute]~ ERROR E0495
-   |        ^^^
-
 error: unsatisfied lifetime constraints
   --> $DIR/project-fn-ret-contravariant.rs:48:4
    |

src/test/ui/associated-types/cache/project-fn-ret-invariant.krisskross.nll.stderr

@@ -1,15 +1,3 @@
-warning: not reporting region error due to nll
-  --> $DIR/project-fn-ret-invariant.rs:63:16
-   |
-LL |    let a = bar(foo, y); //[krisskross]~ ERROR E0623
-   |                ^^^
-
-warning: not reporting region error due to nll
-  --> $DIR/project-fn-ret-invariant.rs:64:16
-   |
-LL |    let b = bar(foo, x);
-   |                ^^^
-
 error: unsatisfied lifetime constraints
   --> $DIR/project-fn-ret-invariant.rs:63:12
    |

src/test/ui/associated-types/cache/project-fn-ret-invariant.oneuse.nll.stderr

@@ -1,9 +1,3 @@
-warning: not reporting region error due to nll
-  --> $DIR/project-fn-ret-invariant.rs:47:12
-   |
-LL |    let f = foo; // <-- No consistent type can be inferred for `f` here.
-   |            ^^^
-
 error: unsatisfied lifetime constraints
   --> $DIR/project-fn-ret-invariant.rs:48:12
    |

src/test/ui/associated-types/cache/project-fn-ret-invariant.transmute.nll.stderr

@@ -1,9 +1,3 @@
-warning: not reporting region error due to nll
-  --> $DIR/project-fn-ret-invariant.rs:58:8
-   |
-LL |    bar(foo, x) //[transmute]~ ERROR E0495
-   |        ^^^
-
 error: unsatisfied lifetime constraints
   --> $DIR/project-fn-ret-invariant.rs:58:4
    |

src/test/ui/borrowck/borrowck-reborrow-from-shorter-lived-andmut.nll.stderr

@@ -1,9 +1,3 @@
-warning: not reporting region error due to nll
-  --> $DIR/borrowck-reborrow-from-shorter-lived-andmut.rs:19:18
-   |
-LL |     S { pointer: &mut *p.pointer }
-   |                  ^^^^^^^^^^^^^^^
-
 error: unsatisfied lifetime constraints
   --> $DIR/borrowck-reborrow-from-shorter-lived-andmut.rs:19:5
    |

src/test/ui/borrowck/issue-45983.nll.stderr

@@ -1,9 +1,3 @@
-warning: not reporting region error due to nll
-  --> $DIR/issue-45983.rs:36:27
-   |
-LL |     give_any(|y| x = Some(y));
-   |                           ^
-
 error: borrowed data escapes outside of closure
   --> $DIR/issue-45983.rs:36:18
    |

src/test/ui/borrowck/issue-45983.rs

@@ -36,7 +36,6 @@ fn main() {
     give_any(|y| x = Some(y));
     //[ast]~^ ERROR borrowed data cannot be stored outside of its closure
     //[migrate]~^^ ERROR borrowed data cannot be stored outside of its closure
-    //[nll]~^^^ WARN not reporting region error due to nll
-    //[nll]~| ERROR borrowed data escapes outside of closure
+    //[nll]~^^^ ERROR borrowed data escapes outside of closure
     //[nll]~| ERROR cannot assign to `x`, as it is not declared as mutable
 }