From d4b59a0da25ab72014ee0aaf7f7e647f1682e083 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Thu, 9 Mar 2023 17:11:30 +0000
Subject: [PATCH] Propagate expected return type instead of real return type in
 check_binop

---
 compiler/rustc_hir_typeck/src/op.rs           |  7 ++--
 .../issues/issue-66667-function-cmp-cycle.rs  |  3 ++
 .../issue-66667-function-cmp-cycle.stderr     | 34 ++++++++++++++++---
 .../cast-checks-handling-projections.rs       |  2 +-
 .../cast-checks-handling-projections.stderr   |  9 -----
 5 files changed, 37 insertions(+), 18 deletions(-)
 delete mode 100644 tests/ui/typeck/lazy-norm/cast-checks-handling-projections.stderr

diff --git a/compiler/rustc_hir_typeck/src/op.rs b/compiler/rustc_hir_typeck/src/op.rs
index eecded557a5..37783bc91bb 100644
--- a/compiler/rustc_hir_typeck/src/op.rs
+++ b/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
             }
         }
     }
diff --git a/tests/ui/issues/issue-66667-function-cmp-cycle.rs b/tests/ui/issues/issue-66667-function-cmp-cycle.rs
index 7b025be11a0..b4f09fbbb04 100644
--- a/tests/ui/issues/issue-66667-function-cmp-cycle.rs
+++ b/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() {}
diff --git a/tests/ui/issues/issue-66667-function-cmp-cycle.stderr b/tests/ui/issues/issue-66667-function-cmp-cycle.stderr
index 887699ef5ce..d9a960ce197 100644
--- a/tests/ui/issues/issue-66667-function-cmp-cycle.stderr
+++ b/tests/ui/issues/issue-66667-function-cmp-cycle.stderr
@@ -15,8 +15,16 @@ 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}
@@ -24,7 +32,7 @@ LL |     first == 1
    |     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
@@ -32,8 +40,16 @@ LL |     first == 1
    = 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}
@@ -41,7 +57,7 @@ LL |     bar == 1
    |     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
@@ -49,7 +65,15 @@ LL |     bar == 1
    = 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`.
diff --git a/tests/ui/typeck/lazy-norm/cast-checks-handling-projections.rs b/tests/ui/typeck/lazy-norm/cast-checks-handling-projections.rs
index 5ff567cd07c..3b261062f78 100644
--- a/tests/ui/typeck/lazy-norm/cast-checks-handling-projections.rs
+++ b/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;
diff --git a/tests/ui/typeck/lazy-norm/cast-checks-handling-projections.stderr b/tests/ui/typeck/lazy-norm/cast-checks-handling-projections.stderr
deleted file mode 100644
index 6b09ccd5214..00000000000
--- a/tests/ui/typeck/lazy-norm/cast-checks-handling-projections.stderr
+++ /dev/null
@@ -1,9 +0,0 @@
-error[E0271]: type mismatch resolving `char == <u8 as Add>::Output`
-  --> $DIR/cast-checks-handling-projections.rs:5:5
-   |
-LL |     (0u8 + 0u8) as char;
-   |     ^^^^^^^^^^^ types differ
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0271`.