Remove return type sized check hack from hir typeck

compiler/rustc_hir_typeck/src/check.rs

@@ -103,24 +103,8 @@ pub(super) fn check_fn<'a, 'tcx>(
 
     fcx.typeck_results.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
 
-    if let ty::Dynamic(_, _, ty::Dyn) = declared_ret_ty.kind() {
-        // FIXME: We need to verify that the return type is `Sized` after the return expression has
-        // been evaluated so that we have types available for all the nodes being returned, but that
-        // requires the coerced evaluated type to be stored. Moving `check_return_expr` before this
-        // causes unsized errors caused by the `declared_ret_ty` to point at the return expression,
-        // while keeping the current ordering we will ignore the tail expression's type because we
-        // don't know it yet. We can't do `check_expr_kind` while keeping `check_return_expr`
-        // because we will trigger "unreachable expression" lints unconditionally.
-        // Because of all of this, we perform a crude check to know whether the simplest `!Sized`
-        // case that a newcomer might make, returning a bare trait, and in that case we populate
-        // the tail expression's type so that the suggestion will be correct, but ignore all other
-        // possible cases.
-        fcx.check_expr(&body.value);
-        fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
-    } else {
-        fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
-        fcx.check_return_expr(&body.value, false);
-    }
+    fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
+    fcx.check_return_expr(&body.value, false);
 
     // We insert the deferred_generator_interiors entry after visiting the body.
     // This ensures that all nested generators appear before the entry of this generator.

tests/ui/impl-trait/dyn-trait-return-should-be-impl-trait.rs

@@ -26,7 +26,7 @@ fn bax() -> dyn Trait { //~ ERROR E0746
     if true {
         Struct
     } else {
-        42 //~ ERROR `if` and `else` have incompatible types
+        42
     }
 }
 fn bam() -> Box<dyn Trait> {

tests/ui/impl-trait/dyn-trait-return-should-be-impl-trait.stderr

@@ -100,18 +100,6 @@ LL |     }
 LL ~     Box::new(42)
    |
 
-error[E0308]: `if` and `else` have incompatible types
-  --> $DIR/dyn-trait-return-should-be-impl-trait.rs:29:9
-   |
-LL | /     if true {
-LL | |         Struct
-   | |         ------ expected because of this
-LL | |     } else {
-LL | |         42
-   | |         ^^ expected `Struct`, found integer
-LL | |     }
-   | |_____- `if` and `else` have incompatible types
-
 error[E0746]: return type cannot have an unboxed trait object
   --> $DIR/dyn-trait-return-should-be-impl-trait.rs:25:13
    |
@@ -305,7 +293,7 @@ LL |     } else {
 LL ~         Box::new(42)
    |
 
-error: aborting due to 20 previous errors
+error: aborting due to 19 previous errors
 
 Some errors have detailed explanations: E0277, E0308, E0746.
 For more information about an error, try `rustc --explain E0277`.

tests/ui/impl-trait/point-to-type-err-cause-on-impl-trait-return.rs

@@ -77,7 +77,7 @@ fn hat() -> dyn std::fmt::Display { //~ ERROR return type cannot have an unboxed
 fn pug() -> dyn std::fmt::Display { //~ ERROR return type cannot have an unboxed trait object
     match 13 {
         0 => 0i32,
-        1 => 1u32, //~ ERROR `match` arms have incompatible types
+        1 => 1u32,
         _ => 2u32,
     }
 }
@@ -86,7 +86,7 @@ fn man() -> dyn std::fmt::Display { //~ ERROR return type cannot have an unboxed
     if false {
         0i32
     } else {
-        1u32 //~ ERROR `if` and `else` have incompatible types
+        1u32
     }
 }
 

tests/ui/impl-trait/point-to-type-err-cause-on-impl-trait-return.stderr

@@ -186,23 +186,6 @@ LL |         _ => {
 LL ~             Box::new(1u32)
    |
 
-error[E0308]: `match` arms have incompatible types
-  --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:80:14
-   |
-LL | /     match 13 {
-LL | |         0 => 0i32,
-   | |              ---- this is found to be of type `i32`
-LL | |         1 => 1u32,
-   | |              ^^^^ expected `i32`, found `u32`
-LL | |         _ => 2u32,
-LL | |     }
-   | |_____- `match` arms have incompatible types
-   |
-help: change the type of the numeric literal from `u32` to `i32`
-   |
-LL |         1 => 1i32,
-   |               ~~~
-
 error[E0746]: return type cannot have an unboxed trait object
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:77:13
    |
@@ -222,23 +205,6 @@ LL ~         1 => Box::new(1u32),
 LL ~         _ => Box::new(2u32),
    |
 
-error[E0308]: `if` and `else` have incompatible types
-  --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:89:9
-   |
-LL | /     if false {
-LL | |         0i32
-   | |         ---- expected because of this
-LL | |     } else {
-LL | |         1u32
-   | |         ^^^^ expected `i32`, found `u32`
-LL | |     }
-   | |_____- `if` and `else` have incompatible types
-   |
-help: change the type of the numeric literal from `u32` to `i32`
-   |
-LL |         1i32
-   |          ~~~
-
 error[E0746]: return type cannot have an unboxed trait object
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:85:13
    |
@@ -258,7 +224,7 @@ LL |     } else {
 LL ~         Box::new(1u32)
    |
 
-error: aborting due to 14 previous errors
+error: aborting due to 12 previous errors
 
 Some errors have detailed explanations: E0308, E0746.
 For more information about an error, try `rustc --explain E0308`.

tests/ui/unsized/box-instead-of-dyn-fn.rs

@@ -8,7 +8,6 @@ fn print_on_or_the_other<'a>(a: i32, b: &'a String) -> dyn Fn() + 'a {
         move || println!("{a}")
     } else {
         Box::new(move || println!("{}", b))
-        //~^ ERROR `if` and `else` have incompatible types
     }
 }
 

tests/ui/unsized/box-instead-of-dyn-fn.stderr

@@ -1,22 +1,3 @@
-error[E0308]: `if` and `else` have incompatible types
-  --> $DIR/box-instead-of-dyn-fn.rs:10:9
-   |
-LL | /     if a % 2 == 0 {
-LL | |         move || println!("{a}")
-   | |         -----------------------
-   | |         |
-   | |         the expected closure
-   | |         expected because of this
-LL | |     } else {
-LL | |         Box::new(move || println!("{}", b))
-   | |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected closure, found `Box<[closure@box-instead-of-dyn-fn.rs:10:18]>`
-LL | |
-LL | |     }
-   | |_____- `if` and `else` have incompatible types
-   |
-   = note: expected closure `[closure@$DIR/box-instead-of-dyn-fn.rs:8:9: 8:16]`
-               found struct `Box<[closure@$DIR/box-instead-of-dyn-fn.rs:10:18: 10:25]>`
-
 error[E0746]: return type cannot have an unboxed trait object
   --> $DIR/box-instead-of-dyn-fn.rs:5:56
    |
@@ -35,7 +16,6 @@ LL |     if a % 2 == 0 {
 LL ~         Box::new(move || println!("{a}"))
    |
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors have detailed explanations: E0308, E0746.
-For more information about an error, try `rustc --explain E0308`.
+For more information about this error, try `rustc --explain E0746`.