Propagate expected return type instead of real return type in check_b…

…inop

compiler/rustc_hir_typeck/src/op.rs

@@ -148,10 +148,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         rhs_ty,
                         op,
                     );
-                    self.demand_suptype(expr.span, builtin_return_ty, return_ty);
+                    self.demand_eqtype(expr.span, builtin_return_ty, return_ty);
+                    builtin_return_ty
+                } else {
+                    return_ty
                 }
-
-                return_ty
             }
         }
     }

tests/ui/issues/issue-66667-function-cmp-cycle.rs

@@ -1,16 +1,19 @@
 fn first() {
     second == 1 //~ ERROR binary operation
     //~^ ERROR mismatched types
+    //~| ERROR mismatched types
 }
 
 fn second() {
     first == 1 //~ ERROR binary operation
     //~^ ERROR mismatched types
+    //~| ERROR mismatched types
 }
 
 fn bar() {
     bar == 1 //~ ERROR binary operation
     //~^ ERROR mismatched types
+    //~| ERROR mismatched types
 }
 
 fn main() {}

tests/ui/issues/issue-66667-function-cmp-cycle.stderr

@@ -15,41 +15,65 @@ LL |     second == 1
    = note: expected fn item `fn() {second}`
                  found type `{integer}`
 
+error[E0308]: mismatched types
+  --> $DIR/issue-66667-function-cmp-cycle.rs:2:5
+   |
+LL | fn first() {
+   |            - help: try adding a return type: `-> bool`
+LL |     second == 1
+   |     ^^^^^^^^^^^ expected `()`, found `bool`
+
 error[E0369]: binary operation `==` cannot be applied to type `fn() {first}`
-  --> $DIR/issue-66667-function-cmp-cycle.rs:7:11
+  --> $DIR/issue-66667-function-cmp-cycle.rs:8:11
    |
 LL |     first == 1
    |     ----- ^^ - {integer}
    |     |
    |     fn() {first}
 
 error[E0308]: mismatched types
-  --> $DIR/issue-66667-function-cmp-cycle.rs:7:14
+  --> $DIR/issue-66667-function-cmp-cycle.rs:8:14
    |
 LL |     first == 1
    |              ^ expected fn item, found integer
    |
    = note: expected fn item `fn() {first}`
                  found type `{integer}`
 
+error[E0308]: mismatched types
+  --> $DIR/issue-66667-function-cmp-cycle.rs:8:5
+   |
+LL | fn second() {
+   |             - help: try adding a return type: `-> bool`
+LL |     first == 1
+   |     ^^^^^^^^^^ expected `()`, found `bool`
+
 error[E0369]: binary operation `==` cannot be applied to type `fn() {bar}`
-  --> $DIR/issue-66667-function-cmp-cycle.rs:12:9
+  --> $DIR/issue-66667-function-cmp-cycle.rs:14:9
    |
 LL |     bar == 1
    |     --- ^^ - {integer}
    |     |
    |     fn() {bar}
 
 error[E0308]: mismatched types
-  --> $DIR/issue-66667-function-cmp-cycle.rs:12:12
+  --> $DIR/issue-66667-function-cmp-cycle.rs:14:12
    |
 LL |     bar == 1
    |            ^ expected fn item, found integer
    |
    = note: expected fn item `fn() {bar}`
                  found type `{integer}`
 
-error: aborting due to 6 previous errors
+error[E0308]: mismatched types
+  --> $DIR/issue-66667-function-cmp-cycle.rs:14:5
+   |
+LL | fn bar() {
+   |          - help: try adding a return type: `-> bool`
+LL |     bar == 1
+   |     ^^^^^^^^ expected `()`, found `bool`
+
+error: aborting due to 9 previous errors
 
 Some errors have detailed explanations: E0308, E0369.
 For more information about an error, try `rustc --explain E0308`.

tests/ui/typeck/lazy-norm/cast-checks-handling-projections.rs

@@ -1,5 +1,5 @@
 // compile-flags: -Ztrait-solver=next
-// known-bug: unknown
+// check-pass
 
 fn main() {
     (0u8 + 0u8) as char;