Rollup merge of rust-lang#65150 - XiangQingW:master, r=estebank

Suggest dereferencing boolean reference when used in 'if' or 'while'

Implements rust-lang#64557

Author: Centril

src/librustc_typeck/check/demand.rs

@@ -349,7 +349,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // If the span is from a macro, then it's hard to extract the text
         // and make a good suggestion, so don't bother.
-        let is_macro = sp.from_expansion();
+        let is_desugaring = match sp.desugaring_kind() {
+            Some(k) => sp.is_desugaring(k),
+            None => false
+        };
+        let is_macro = sp.from_expansion() && !is_desugaring;
 
         match (&expr.kind, &expected.kind, &checked_ty.kind) {
             (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (&exp.kind, &check.kind) {

src/librustc_typeck/check/expr.rs

@@ -87,6 +87,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) {
+            self.suggest_ref_or_into(&mut err, expr, expected_ty, ty);
+
             let expr = match &expr.kind {
                 ExprKind::DropTemps(expr) => expr,
                 _ => expr,

src/test/ui/if/if-no-match-bindings.stderr

@@ -2,7 +2,10 @@ error[E0308]: mismatched types
   --> $DIR/if-no-match-bindings.rs:18:8
    |
 LL |     if b_ref() {}
-   |        ^^^^^^^ expected bool, found &bool
+   |        ^^^^^^^
+   |        |
+   |        expected bool, found &bool
+   |        help: consider dereferencing the borrow: `*b_ref()`
    |
    = note: expected type `bool`
               found type `&bool`
@@ -11,7 +14,10 @@ error[E0308]: mismatched types
   --> $DIR/if-no-match-bindings.rs:19:8
    |
 LL |     if b_mut_ref() {}
-   |        ^^^^^^^^^^^ expected bool, found &mut bool
+   |        ^^^^^^^^^^^
+   |        |
+   |        expected bool, found &mut bool
+   |        help: consider dereferencing the borrow: `*b_mut_ref()`
    |
    = note: expected type `bool`
               found type `&mut bool`
@@ -20,7 +26,10 @@ error[E0308]: mismatched types
   --> $DIR/if-no-match-bindings.rs:20:8
    |
 LL |     if &true {}
-   |        ^^^^^ expected bool, found &bool
+   |        ^^^^^
+   |        |
+   |        expected bool, found &bool
+   |        help: consider dereferencing the borrow: `*&true`
    |
    = note: expected type `bool`
               found type `&bool`
@@ -29,7 +38,10 @@ error[E0308]: mismatched types
   --> $DIR/if-no-match-bindings.rs:21:8
    |
 LL |     if &mut true {}
-   |        ^^^^^^^^^ expected bool, found &mut bool
+   |        ^^^^^^^^^
+   |        |
+   |        expected bool, found &mut bool
+   |        help: consider dereferencing the borrow: `*&mut true`
    |
    = note: expected type `bool`
               found type `&mut bool`
@@ -38,7 +50,10 @@ error[E0308]: mismatched types
   --> $DIR/if-no-match-bindings.rs:24:11
    |
 LL |     while b_ref() {}
-   |           ^^^^^^^ expected bool, found &bool
+   |           ^^^^^^^
+   |           |
+   |           expected bool, found &bool
+   |           help: consider dereferencing the borrow: `*b_ref()`
    |
    = note: expected type `bool`
               found type `&bool`
@@ -47,7 +62,10 @@ error[E0308]: mismatched types
   --> $DIR/if-no-match-bindings.rs:25:11
    |
 LL |     while b_mut_ref() {}
-   |           ^^^^^^^^^^^ expected bool, found &mut bool
+   |           ^^^^^^^^^^^
+   |           |
+   |           expected bool, found &mut bool
+   |           help: consider dereferencing the borrow: `*b_mut_ref()`
    |
    = note: expected type `bool`
               found type `&mut bool`
@@ -56,7 +74,10 @@ error[E0308]: mismatched types
   --> $DIR/if-no-match-bindings.rs:26:11
    |
 LL |     while &true {}
-   |           ^^^^^ expected bool, found &bool
+   |           ^^^^^
+   |           |
+   |           expected bool, found &bool
+   |           help: consider dereferencing the borrow: `*&true`
    |
    = note: expected type `bool`
               found type `&bool`
@@ -65,7 +86,10 @@ error[E0308]: mismatched types
   --> $DIR/if-no-match-bindings.rs:27:11
    |
 LL |     while &mut true {}
-   |           ^^^^^^^^^ expected bool, found &mut bool
+   |           ^^^^^^^^^
+   |           |
+   |           expected bool, found &mut bool
+   |           help: consider dereferencing the borrow: `*&mut true`
    |
    = note: expected type `bool`
               found type `&mut bool`

src/test/ui/rfc-2497-if-let-chains/disallowed-positions.stderr

@@ -517,7 +517,10 @@ error[E0308]: mismatched types
   --> $DIR/disallowed-positions.rs:32:8
    |
 LL |     if &let 0 = 0 {}
-   |        ^^^^^^^^^^ expected bool, found &bool
+   |        ^^^^^^^^^^
+   |        |
+   |        expected bool, found &bool
+   |        help: consider dereferencing the borrow: `*&let 0 = 0`
    |
    = note: expected type `bool`
               found type `&bool`
@@ -702,7 +705,10 @@ error[E0308]: mismatched types
   --> $DIR/disallowed-positions.rs:96:11
    |
 LL |     while &let 0 = 0 {}
-   |           ^^^^^^^^^^ expected bool, found &bool
+   |           ^^^^^^^^^^
+   |           |
+   |           expected bool, found &bool
+   |           help: consider dereferencing the borrow: `*&let 0 = 0`
    |
    = note: expected type `bool`
               found type `&bool`