Add deref definition location

Update conflict_errors.rs

Add deref definition location

Author: sledgehammervampire

compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs

@@ -1568,6 +1568,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         "borrow occurs due to deref coercion to `{}`",
                         deref_target_ty
                     ));
+                    err.span_note(tcx.def_span(instance.def_id()), "deref defined here");
                 }
             }
         }

src/test/ui/borrowck/issue-81365-1.stderr

@@ -9,6 +9,11 @@ LL |         first;
    |         ----- borrow later used here
    |
    = note: borrow occurs due to deref coercion to `DerefTarget`
+note: deref defined here
+  --> $DIR/issue-81365-1.rs:12:5
+   |
+LL |     type Target = DerefTarget;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/borrowck/issue-81365-2.stderr

@@ -9,6 +9,11 @@ LL |         first;
    |         ----- borrow later used here
    |
    = note: borrow occurs due to deref coercion to `DerefTarget`
+note: deref defined here
+  --> $DIR/issue-81365-2.rs:12:5
+   |
+LL |     type Target = DerefTarget;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/borrowck/issue-81365-3.stderr

@@ -9,6 +9,11 @@ LL |         first;
    |         ----- borrow later used here
    |
    = note: borrow occurs due to deref coercion to `Container`
+note: deref defined here
+  --> $DIR/issue-81365-3.rs:23:5
+   |
+LL |     type Target = Container;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/borrowck/issue-81365-4.stderr

@@ -9,6 +9,11 @@ LL |         first;
    |         ----- borrow later used here
    |
    = note: borrow occurs due to deref coercion to `Container`
+note: deref defined here
+  --> $DIR/issue-81365-4.rs:24:5
+   |
+LL |     type Target = Container;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/borrowck/issue-81365-5.stderr

@@ -9,6 +9,11 @@ LL |         first;
    |         ----- borrow later used here
    |
    = note: borrow occurs due to deref coercion to `DerefTarget`
+note: deref defined here
+  --> $DIR/issue-81365-5.rs:19:5
+   |
+LL |     type Target = DerefTarget;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/borrowck/issue-81365-6.stderr

@@ -9,6 +9,11 @@ LL |         first;
    |         ----- borrow later used here
    |
    = note: borrow occurs due to deref coercion to `[()]`
+note: deref defined here
+  --> $DIR/issue-81365-6.rs:9:5
+   |
+LL |     type Target = [()];
+   |     ^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/borrowck/issue-81365-7.stderr

@@ -9,6 +9,11 @@ LL |     first;
    |     ----- borrow later used here
    |
    = note: borrow occurs due to deref coercion to `DerefTarget`
+note: deref defined here
+  --> $DIR/issue-81365-7.rs:12:5
+   |
+LL |     type Target = DerefTarget;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/borrowck/issue-81365-8.stderr

@@ -9,6 +9,11 @@ LL |         first;
    |         ----- borrow later used here
    |
    = note: borrow occurs due to deref coercion to `DerefTarget`
+note: deref defined here
+  --> $DIR/issue-81365-8.rs:12:5
+   |
+LL |     type Target = DerefTarget;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error