Resolve vars before emitting coerce error

11 files changed, 102 insertions, 12 deletions

diff --git a/compiler/rustc_typeck/src/check/coercion.rs b/compiler/rustc_typeck/src/check/coercion.rs
index b75a2f3edd9..b659eab5ca4 100644
--- a/compiler/rustc_typeck/src/check/coercion.rs
+++ b/compiler/rustc_typeck/src/check/coercion.rs
@@ -1478,6 +1478,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                     // type)
                     (self.final_ty.unwrap_or(self.expected_ty), expression_ty)
                 };
+                let (expected, found) = fcx.resolve_vars_if_possible((expected, found));
 
                 let mut err;
                 let mut unsized_return = false;
@@ -1663,7 +1664,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                 sp,
                 &format!(
                     "return type inferred to be `{}` here",
-                    fcx.resolve_vars_if_possible(expected)
+                    expected
                 ),
             );
         }
diff --git a/src/test/ui/expr/if/if-branch-types.stderr b/src/test/ui/expr/if/if-branch-types.stderr
index 14f02163a83..d2bba88211e 100644
--- a/src/test/ui/expr/if/if-branch-types.stderr
+++ b/src/test/ui/expr/if/if-branch-types.stderr
@@ -5,6 +5,11 @@ LL |     let x = if true { 10i32 } else { 10u32 };
    |                       -----          ^^^^^ expected `i32`, found `u32`
    |                       |
    |                       expected because of this
+   |
+help: change the type of the numeric literal from `u32` to `i32`
+   |
+LL |     let x = if true { 10i32 } else { 10i32 };
+   |                                        ~~~
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/expr/if/if-else-type-mismatch.stderr b/src/test/ui/expr/if/if-else-type-mismatch.stderr
index 9fa190d6c9d..f1fffdb1e7e 100644
--- a/src/test/ui/expr/if/if-else-type-mismatch.stderr
+++ b/src/test/ui/expr/if/if-else-type-mismatch.stderr
@@ -10,6 +10,11 @@ LL | |         2u32
    | |         ^^^^ expected `i32`, found `u32`
 LL | |     };
    | |_____- `if` and `else` have incompatible types
+   |
+help: change the type of the numeric literal from `u32` to `i32`
+   |
+LL |         2i32
+   |          ~~~
 
 error[E0308]: `if` and `else` have incompatible types
   --> $DIR/if-else-type-mismatch.rs:8:38
@@ -18,6 +23,11 @@ LL |     let _ = if true { 42i32 } else { 42u32 };
    |                       -----          ^^^^^ expected `i32`, found `u32`
    |                       |
    |                       expected because of this
+   |
+help: change the type of the numeric literal from `u32` to `i32`
+   |
+LL |     let _ = if true { 42i32 } else { 42i32 };
+   |                                        ~~~
 
 error[E0308]: `if` and `else` have incompatible types
   --> $DIR/if-else-type-mismatch.rs:13:9
diff --git a/src/test/ui/generator/type-mismatch-signature-deduction.stderr b/src/test/ui/generator/type-mismatch-signature-deduction.stderr
index 7938fc8097c..b98da1ed8be 100644
--- a/src/test/ui/generator/type-mismatch-signature-deduction.stderr
+++ b/src/test/ui/generator/type-mismatch-signature-deduction.stderr
@@ -11,6 +11,12 @@ note: return type inferred to be `Result<{integer}, _>` here
    |
 LL |             return Ok(6);
    |                    ^^^^^
+help: try wrapping the expression in a variant of `Result`
+   |
+LL |         Ok(5)
+   |         +++ +
+LL |         Err(5)
+   |         ++++ +
 
 error[E0271]: type mismatch resolving `<[generator@$DIR/type-mismatch-signature-deduction.rs:7:5: 7:7] as Generator>::Return == i32`
   --> $DIR/type-mismatch-signature-deduction.rs:5:13
diff --git a/src/test/ui/impl-trait/equality.stderr b/src/test/ui/impl-trait/equality.stderr
index f14b447b077..d4a3495515c 100644
--- a/src/test/ui/impl-trait/equality.stderr
+++ b/src/test/ui/impl-trait/equality.stderr
@@ -12,10 +12,15 @@ error[E0308]: mismatched types
   --> $DIR/equality.rs:15:5
    |
 LL | fn two(x: bool) -> impl Foo {
-   |                    -------- expected `_` because of return type
+   |                    -------- expected `i32` because of return type
 ...
 LL |     0_u32
    |     ^^^^^ expected `i32`, found `u32`
+   |
+help: change the type of the numeric literal from `u32` to `i32`
+   |
+LL |     0_i32
+   |       ~~~
 
 error[E0277]: cannot add `impl Foo` to `u32`
   --> $DIR/equality.rs:24:11
diff --git a/src/test/ui/impl-trait/object-unsafe-trait-in-return-position-impl-trait.stderr b/src/test/ui/impl-trait/object-unsafe-trait-in-return-position-impl-trait.stderr
index 5ca01a59376..d6f5a1ac25b 100644
--- a/src/test/ui/impl-trait/object-unsafe-trait-in-return-position-impl-trait.stderr
+++ b/src/test/ui/impl-trait/object-unsafe-trait-in-return-position-impl-trait.stderr
@@ -2,7 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/object-unsafe-trait-in-return-position-impl-trait.rs:36:5
    |
 LL | fn can() -> impl NotObjectSafe {
-   |             ------------------ expected `_` because of return type
+   |             ------------------ expected `A` because of return type
 ...
 LL |     B
    |     ^ expected struct `A`, found struct `B`
@@ -11,7 +11,7 @@ error[E0308]: mismatched types
   --> $DIR/object-unsafe-trait-in-return-position-impl-trait.rs:43:5
    |
 LL | fn cat() -> impl ObjectSafe {
-   |             --------------- expected `_` because of return type
+   |             --------------- expected `A` because of return type
 ...
 LL |     B
    |     ^ expected struct `A`, found struct `B`
diff --git a/src/test/ui/impl-trait/point-to-type-err-cause-on-impl-trait-return.stderr b/src/test/ui/impl-trait/point-to-type-err-cause-on-impl-trait-return.stderr
index 10510c1754e..11c1072f02c 100644
--- a/src/test/ui/impl-trait/point-to-type-err-cause-on-impl-trait-return.stderr
+++ b/src/test/ui/impl-trait/point-to-type-err-cause-on-impl-trait-return.stderr
@@ -2,28 +2,43 @@ error[E0308]: mismatched types
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:5:5
    |
 LL | fn foo() -> impl std::fmt::Display {
-   |             ---------------------- expected `_` because of return type
+   |             ---------------------- expected `i32` because of return type
 ...
 LL |     1u32
    |     ^^^^ expected `i32`, found `u32`
+   |
+help: change the type of the numeric literal from `u32` to `i32`
+   |
+LL |     1i32
+   |      ~~~
 
 error[E0308]: mismatched types
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:12:16
    |
 LL | fn bar() -> impl std::fmt::Display {
-   |             ---------------------- expected `_` because of return type
+   |             ---------------------- expected `i32` because of return type
 ...
 LL |         return 1u32;
    |                ^^^^ expected `i32`, found `u32`
+   |
+help: change the type of the numeric literal from `u32` to `i32`
+   |
+LL |         return 1i32;
+   |                 ~~~
 
 error[E0308]: mismatched types
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:20:9
    |
 LL | fn baz() -> impl std::fmt::Display {
-   |             ---------------------- expected `_` because of return type
+   |             ---------------------- expected `i32` because of return type
 ...
 LL |         1u32
    |         ^^^^ expected `i32`, found `u32`
+   |
+help: you can convert a `u32` to an `i32` and panic if the converted value doesn't fit
+   |
+LL |     }.try_into().unwrap()
+   |      ++++++++++++++++++++
 
 error[E0308]: `if` and `else` have incompatible types
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:28:9
@@ -36,36 +51,56 @@ 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[E0308]: mismatched types
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:35:14
    |
 LL | fn bat() -> impl std::fmt::Display {
-   |             ---------------------- expected `_` because of return type
+   |             ---------------------- expected `i32` because of return type
 ...
 LL |         _ => 1u32,
    |              ^^^^ expected `i32`, found `u32`
+   |
+help: you can convert a `u32` to an `i32` and panic if the converted value doesn't fit
+   |
+LL |     }.try_into().unwrap()
+   |      ++++++++++++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:40:5
    |
 LL |   fn can() -> impl std::fmt::Display {
-   |               ---------------------- expected `_` because of return type
+   |               ---------------------- expected `i32` because of return type
 LL | /     match 13 {
 LL | |         0 => return 0i32,
 LL | |         1 => 1u32,
 LL | |         _ => 2u32,
 LL | |     }
    | |_____^ expected `i32`, found `u32`
+   |
+help: you can convert a `u32` to an `i32` and panic if the converted value doesn't fit
+   |
+LL |     }.try_into().unwrap()
+   |      ++++++++++++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:53:13
    |
 LL | fn cat() -> impl std::fmt::Display {
-   |             ---------------------- expected `_` because of return type
+   |             ---------------------- expected `i32` because of return type
 ...
 LL |             1u32
    |             ^^^^ expected `i32`, found `u32`
+   |
+help: you can convert a `u32` to an `i32` and panic if the converted value doesn't fit
+   |
+LL |     }.try_into().unwrap()
+   |      ++++++++++++++++++++
 
 error[E0308]: `match` arms have incompatible types
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:61:14
@@ -78,6 +113,11 @@ LL | |         1 => 1u32,
 LL | |         _ => 2u32,
 LL | |     }
    | |_____- `match` arms have incompatible types
+   |
+help: change the type of the numeric literal from `u32` to `i32`
+   |
+LL |         1 => 1i32,
+   |               ~~~
 
 error[E0308]: `if` and `else` have incompatible types
   --> $DIR/point-to-type-err-cause-on-impl-trait-return.rs:97:9
@@ -90,6 +130,11 @@ 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:66:13
@@ -125,6 +170,11 @@ LL | |         1 => 1u32,
 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
@@ -164,6 +214,11 @@ 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
diff --git a/src/test/ui/mismatched_types/dont-point-return-on-E0308.stderr b/src/test/ui/mismatched_types/dont-point-return-on-E0308.stderr
index e79ab537b4c..13942682d28 100644
--- a/src/test/ui/mismatched_types/dont-point-return-on-E0308.stderr
+++ b/src/test/ui/mismatched_types/dont-point-return-on-E0308.stderr
@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/dont-point-return-on-E0308.rs:10:11
+  --> $DIR/dont-point-return-on-E0308.rs:11:11
    |
 LL |         f(());
    |         - ^^
diff --git a/src/test/ui/mismatched_types/issue-84976.stderr b/src/test/ui/mismatched_types/issue-84976.stderr
index f8f2b1f0f57..9157566e3a7 100644
--- a/src/test/ui/mismatched_types/issue-84976.stderr
+++ b/src/test/ui/mismatched_types/issue-84976.stderr
@@ -3,6 +3,11 @@ error[E0308]: mismatched types
    |
 LL |     length = { foo(&length) };
    |                ^^^^^^^^^^^^ expected `u32`, found `i32`
+   |
+help: you can convert an `i32` to a `u32` and panic if the converted value doesn't fit
+   |
+LL |     length = { foo(&length).try_into().unwrap() };
+   |                            ++++++++++++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/issue-84976.rs:17:14
diff --git a/src/test/ui/reify-intrinsic.stderr b/src/test/ui/reify-intrinsic.stderr
index 360557fb520..f78f1d822bf 100644
--- a/src/test/ui/reify-intrinsic.stderr
+++ b/src/test/ui/reify-intrinsic.stderr
@@ -23,6 +23,9 @@ LL |         std::intrinsics::unlikely,
    |
    = note: expected fn item `extern "rust-intrinsic" fn(_) -> _ {likely}`
               found fn item `extern "rust-intrinsic" fn(_) -> _ {unlikely}`
+   = note: different `fn` items always have unique types, even if their signatures are the same
+   = help: change the expected type to be function pointer `extern "rust-intrinsic" fn(bool) -> bool`
+   = help: if the expected type is due to type inference, cast the expected `fn` to a function pointer: `likely as extern "rust-intrinsic" fn(bool) -> bool`
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/type-alias-impl-trait/issue-74280.stderr b/src/test/ui/type-alias-impl-trait/issue-74280.stderr
index 5ed29e0ac94..66886db6eb9 100644
--- a/src/test/ui/type-alias-impl-trait/issue-74280.stderr
+++ b/src/test/ui/type-alias-impl-trait/issue-74280.stderr
@@ -2,7 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-74280.rs:9:5
    |
 LL | fn test() -> Test {
-   |              ---- expected `_` because of return type
+   |              ---- expected `()` because of return type
 LL |     let y = || -> Test { () };
 LL |     7
    |     ^ expected `()`, found integer