Fix "mir_build_multiple_mut_borrows"

Author: mejrs

compiler/rustc_mir_build/src/errors.rs

@@ -586,7 +586,7 @@ pub struct MultipleMutBorrows {
     pub span: Span,
     #[label]
     pub binding_span: Span,
-    #[subdiagnostic]
+    #[subdiagnostic(eager)]
     pub occurences: Vec<MultipleMutBorrowOccurence>,
     pub name: Ident,
 }

src/test/ui/pattern/bindings-after-at/borrowck-pat-ref-mut-twice.stderr

@@ -53,10 +53,10 @@ LL |       let ref mut a @ (
    | |
 LL | |
 LL | |         ref mut b,
-   | |         --------- another mutable borrow, by `d`, occurs here
+   | |         --------- another mutable borrow, by `b`, occurs here
 LL | |         [
 LL | |             ref mut c,
-   | |             --------- another mutable borrow, by `d`, occurs here
+   | |             --------- another mutable borrow, by `c`, occurs here
 LL | |             ref mut d,
    | |             --------- another mutable borrow, by `d`, occurs here
 LL | |             ref e,
@@ -75,10 +75,10 @@ LL |       let ref mut a @ (
    | |
 LL | |
 LL | |             ref mut b,
-   | |             --------- another mutable borrow, by `d`, occurs here
+   | |             --------- another mutable borrow, by `b`, occurs here
 LL | |             [
 LL | |                 ref mut c,
-   | |                 --------- another mutable borrow, by `d`, occurs here
+   | |                 --------- another mutable borrow, by `c`, occurs here
 LL | |                 ref mut d,
    | |                 --------- another mutable borrow, by `d`, occurs here
 LL | |                 ref e,