Rollup merge of #91981 - estebank:tweakaroo, r=lcnr

Recover suggestions and useful information lost in previous PR

Follow up to #91898.

41 files changed, 209 insertions, 60 deletions

diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index abc25d51776..238145c5c6e 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -333,6 +333,9 @@ pub fn same_type_modulo_infer<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
         )
         | (&ty::Infer(ty::InferTy::TyVar(_)), _)
         | (_, &ty::Infer(ty::InferTy::TyVar(_))) => true,
+        (&ty::Ref(reg_a, ty_a, mut_a), &ty::Ref(reg_b, ty_b, mut_b)) => {
+            reg_a == reg_b && mut_a == mut_b && same_type_modulo_infer(*ty_a, *ty_b)
+        }
         _ => a == b,
     }
 }
@@ -602,7 +605,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         match *cause.code() {
             ObligationCauseCode::Pattern { origin_expr: true, span: Some(span), root_ty } => {
                 let ty = self.resolve_vars_if_possible(root_ty);
-                if ty.is_suggestable() {
+                if !matches!(ty.kind(), ty::Infer(ty::InferTy::TyVar(_) | ty::InferTy::FreshTy(_)))
+                {
                     // don't show type `_`
                     err.span_label(span, format!("this expression has type `{}`", ty));
                 }
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index 2886d921c70..83ba9c96978 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -1434,6 +1434,17 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         value.fold_with(&mut r)
     }
 
+    pub fn resolve_numeric_literals_with_default<T>(&self, value: T) -> T
+    where
+        T: TypeFoldable<'tcx>,
+    {
+        if !value.needs_infer() {
+            return value; // Avoid duplicated subst-folding.
+        }
+        let mut r = InferenceLiteralEraser { tcx: self.tcx };
+        value.fold_with(&mut r)
+    }
+
     /// Returns the first unresolved variable contained in `T`. In the
     /// process of visiting `T`, this will resolve (where possible)
     /// type variables in `T`, but it never constructs the final,
@@ -1785,6 +1796,26 @@ impl<'tcx> TyOrConstInferVar<'tcx> {
     }
 }
 
+/// Replace `{integer}` with `i32` and `{float}` with `f64`.
+/// Used only for diagnostics.
+struct InferenceLiteralEraser<'tcx> {
+    tcx: TyCtxt<'tcx>,
+}
+
+impl<'tcx> TypeFolder<'tcx> for InferenceLiteralEraser<'tcx> {
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.tcx
+    }
+
+    fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
+        match ty.kind() {
+            ty::Infer(ty::IntVar(_) | ty::FreshIntTy(_)) => self.tcx.types.i32,
+            ty::Infer(ty::FloatVar(_) | ty::FreshFloatTy(_)) => self.tcx.types.f64,
+            _ => ty.super_fold_with(self),
+        }
+    }
+}
+
 struct ShallowResolver<'a, 'tcx> {
     infcx: &'a InferCtxt<'a, 'tcx>,
 }
diff --git a/compiler/rustc_typeck/src/astconv/generics.rs b/compiler/rustc_typeck/src/astconv/generics.rs
index 754172b1158..a07700aa9f5 100644
--- a/compiler/rustc_typeck/src/astconv/generics.rs
+++ b/compiler/rustc_typeck/src/astconv/generics.rs
@@ -11,6 +11,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::GenericArg;
+use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::ty::{
     self, subst, subst::SubstsRef, GenericParamDef, GenericParamDefKind, Ty, TyCtxt,
 };
@@ -83,7 +84,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     if let Some(param_local_id) = param.def_id.as_local() {
                         let param_hir_id = tcx.hir().local_def_id_to_hir_id(param_local_id);
                         let param_name = tcx.hir().ty_param_name(param_hir_id);
-                        let param_type = tcx.type_of(param.def_id);
+                        let param_type = tcx.infer_ctxt().enter(|infcx| {
+                            infcx.resolve_numeric_literals_with_default(tcx.type_of(param.def_id))
+                        });
                         if param_type.is_suggestable() {
                             err.span_suggestion(
                                 tcx.def_span(src_def_id),
diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs b/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs
index 67d61668b6d..e6a98ad6dc0 100644
--- a/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs
@@ -521,6 +521,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         can_suggest: bool,
         fn_id: hir::HirId,
     ) -> bool {
+        let found =
+            self.resolve_numeric_literals_with_default(self.resolve_vars_if_possible(found));
         // Only suggest changing the return type for methods that
         // haven't set a return type at all (and aren't `fn main()` or an impl).
         match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
@@ -528,13 +530,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 err.span_suggestion(
                     span,
                     "try adding a return type",
-                    format!("-> {} ", self.resolve_vars_with_obligations(found)),
+                    format!("-> {} ", found),
                     Applicability::MachineApplicable,
                 );
                 true
             }
             (&hir::FnRetTy::DefaultReturn(span), false, true, true) => {
-                err.span_label(span, "possibly return type missing here?");
+                // FIXME: if `found` could be `impl Iterator` or `impl Fn*`, we should suggest
+                // that.
+                err.span_suggestion(
+                    span,
+                    "a return type might be missing here",
+                    "-> _ ".to_string(),
+                    Applicability::HasPlaceholders,
+                );
                 true
             }
             (&hir::FnRetTy::DefaultReturn(span), _, false, true) => {
diff --git a/src/test/ui/async-await/issue-61076.rs b/src/test/ui/async-await/issue-61076.rs
index a94136cfea1..750fad8393b 100644
--- a/src/test/ui/async-await/issue-61076.rs
+++ b/src/test/ui/async-await/issue-61076.rs
@@ -87,6 +87,7 @@ async fn baz() -> Result<(), ()> {
 
 async fn match_() {
     match tuple() { //~ HELP consider `await`ing on the `Future`
+        //~^ NOTE this expression has type `impl Future<Output = Tuple>`
         Tuple(_) => {} //~ ERROR mismatched types
         //~^ NOTE expected opaque type, found struct `Tuple`
         //~| NOTE expected opaque type `impl Future<Output = Tuple>`
diff --git a/src/test/ui/async-await/issue-61076.stderr b/src/test/ui/async-await/issue-61076.stderr
index 65c0bc695bf..33839ea5939 100644
--- a/src/test/ui/async-await/issue-61076.stderr
+++ b/src/test/ui/async-await/issue-61076.stderr
@@ -56,8 +56,11 @@ LL |     struct_().await.method();
    |               ++++++
 
 error[E0308]: mismatched types
-  --> $DIR/issue-61076.rs:90:9
+  --> $DIR/issue-61076.rs:91:9
    |
+LL |     match tuple() {
+   |           ------- this expression has type `impl Future<Output = Tuple>`
+LL |
 LL |         Tuple(_) => {}
    |         ^^^^^^^^ expected opaque type, found struct `Tuple`
    |
diff --git a/src/test/ui/async-await/suggest-missing-await.stderr b/src/test/ui/async-await/suggest-missing-await.stderr
index 3cca9616a35..76073c4c879 100644
--- a/src/test/ui/async-await/suggest-missing-await.stderr
+++ b/src/test/ui/async-await/suggest-missing-await.stderr
@@ -91,6 +91,8 @@ LL ~         1 => dummy().await,
 error[E0308]: mismatched types
   --> $DIR/suggest-missing-await.rs:53:9
    |
+LL |     let _x = match dummy() {
+   |                    ------- this expression has type `impl Future<Output = ()>`
 LL |         () => {}
    |         ^^ expected opaque type, found `()`
    |
@@ -109,6 +111,9 @@ LL |     let _x = match dummy().await {
 error[E0308]: mismatched types
   --> $DIR/suggest-missing-await.rs:67:9
    |
+LL |     match dummy_result() {
+   |           -------------- this expression has type `impl Future<Output = Result<(), ()>>`
+...
 LL |         Ok(_) => {}
    |         ^^^^^ expected opaque type, found enum `Result`
    |
@@ -127,6 +132,9 @@ LL |     match dummy_result().await {
 error[E0308]: mismatched types
   --> $DIR/suggest-missing-await.rs:69:9
    |
+LL |     match dummy_result() {
+   |           -------------- this expression has type `impl Future<Output = Result<(), ()>>`
+...
 LL |         Err(_) => {}
    |         ^^^^^^ expected opaque type, found enum `Result`
    |
diff --git a/src/test/ui/blind/blind-item-block-middle.stderr b/src/test/ui/blind/blind-item-block-middle.stderr
index 9db11cf1590..dd83f6edf62 100644
--- a/src/test/ui/blind/blind-item-block-middle.stderr
+++ b/src/test/ui/blind/blind-item-block-middle.stderr
@@ -5,7 +5,7 @@ LL | mod foo { pub struct bar; }
    |           --------------- unit struct defined here
 ...
 LL |     let bar = 5;
-   |         ^^^
+   |         ^^^   - this expression has type `{integer}`
    |         |
    |         expected integer, found struct `bar`
    |         `bar` is interpreted as a unit struct, not a new binding
diff --git a/src/test/ui/block-result/issue-20862.stderr b/src/test/ui/block-result/issue-20862.stderr
index 09c06e8428d..e9ca0ad9029 100644
--- a/src/test/ui/block-result/issue-20862.stderr
+++ b/src/test/ui/block-result/issue-20862.stderr
@@ -2,7 +2,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-20862.rs:2:5
    |
 LL | fn foo(x: i32) {
-   |                - possibly return type missing here?
+   |                - help: a return type might be missing here: `-> _`
 LL |     |y| x + y
    |     ^^^^^^^^^ expected `()`, found closure
    |
diff --git a/src/test/ui/destructuring-assignment/default-match-bindings-forbidden.stderr b/src/test/ui/destructuring-assignment/default-match-bindings-forbidden.stderr
index 2250f561b54..3d472bf6309 100644
--- a/src/test/ui/destructuring-assignment/default-match-bindings-forbidden.stderr
+++ b/src/test/ui/destructuring-assignment/default-match-bindings-forbidden.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/default-match-bindings-forbidden.rs:4:5
    |
 LL |     (x, y) = &(1, 2);
-   |     ^^^^^^ expected reference, found tuple
+   |     ^^^^^^   ------- this expression has type `&({integer}, {integer})`
+   |     |
+   |     expected reference, found tuple
    |
    = note: expected type `&({integer}, {integer})`
              found tuple `(_, _)`
diff --git a/src/test/ui/destructuring-assignment/tuple_destructure_fail.stderr b/src/test/ui/destructuring-assignment/tuple_destructure_fail.stderr
index 184b3ea6da8..55b08b74af0 100644
--- a/src/test/ui/destructuring-assignment/tuple_destructure_fail.stderr
+++ b/src/test/ui/destructuring-assignment/tuple_destructure_fail.stderr
@@ -10,7 +10,9 @@ error[E0308]: mismatched types
   --> $DIR/tuple_destructure_fail.rs:6:5
    |
 LL |     (a, a, b) = (1, 2);
-   |     ^^^^^^^^^ expected a tuple with 2 elements, found one with 3 elements
+   |     ^^^^^^^^^   ------ this expression has type `({integer}, {integer})`
+   |     |
+   |     expected a tuple with 2 elements, found one with 3 elements
    |
    = note: expected type `({integer}, {integer})`
              found tuple `(_, _, _)`
@@ -27,7 +29,9 @@ error[E0308]: mismatched types
   --> $DIR/tuple_destructure_fail.rs:8:5
    |
 LL |     (_,) = (1, 2);
-   |     ^^^^ expected a tuple with 2 elements, found one with 1 element
+   |     ^^^^   ------ this expression has type `({integer}, {integer})`
+   |     |
+   |     expected a tuple with 2 elements, found one with 1 element
    |
    = note: expected type `({integer}, {integer})`
              found tuple `(_,)`
diff --git a/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision.stderr b/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision.stderr
index 241485db49b..a6f8563a047 100644
--- a/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision.stderr
+++ b/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/exclusive_range_pattern_syntax_collision.rs:6:13
    |
+LL |     match [5..4, 99..105, 43..44] {
+   |           ----------------------- this expression has type `[std::ops::Range<{integer}>; 3]`
 LL |         [_, 99.., _] => {},
    |             ^^ expected struct `std::ops::Range`, found integer
    |
diff --git a/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision2.stderr b/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision2.stderr
index 777d029d7dd..4e0102c930d 100644
--- a/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision2.stderr
+++ b/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision2.stderr
@@ -7,6 +7,8 @@ LL |         [_, 99..] => {},
 error[E0308]: mismatched types
   --> $DIR/exclusive_range_pattern_syntax_collision2.rs:6:13
    |
+LL |     match [5..4, 99..105, 43..44] {
+   |           ----------------------- this expression has type `[std::ops::Range<{integer}>; 3]`
 LL |         [_, 99..] => {},
    |             ^^ expected struct `std::ops::Range`, found integer
    |
diff --git a/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision3.stderr b/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision3.stderr
index 6119733a7d8..665eef2fcb9 100644
--- a/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision3.stderr
+++ b/src/test/ui/half-open-range-patterns/exclusive_range_pattern_syntax_collision3.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/exclusive_range_pattern_syntax_collision3.rs:6:12
    |
+LL |     match [5..4, 99..105, 43..44] {
+   |           ----------------------- this expression has type `[std::ops::Range<{integer}>; 3]`
 LL |         [..9, 99..100, _] => {},
    |            ^ expected struct `std::ops::Range`, found integer
    |
@@ -10,6 +12,8 @@ LL |         [..9, 99..100, _] => {},
 error[E0308]: mismatched types
   --> $DIR/exclusive_range_pattern_syntax_collision3.rs:6:15
    |
+LL |     match [5..4, 99..105, 43..44] {
+   |           ----------------------- this expression has type `[std::ops::Range<{integer}>; 3]`
 LL |         [..9, 99..100, _] => {},
    |               ^^  --- this is of type `{integer}`
    |               |
@@ -21,6 +25,8 @@ LL |         [..9, 99..100, _] => {},
 error[E0308]: mismatched types
   --> $DIR/exclusive_range_pattern_syntax_collision3.rs:6:19
    |
+LL |     match [5..4, 99..105, 43..44] {
+   |           ----------------------- this expression has type `[std::ops::Range<{integer}>; 3]`
 LL |         [..9, 99..100, _] => {},
    |               --  ^^^ expected struct `std::ops::Range`, found integer
    |               |
diff --git a/src/test/ui/half-open-range-patterns/pat-tuple-5.stderr b/src/test/ui/half-open-range-patterns/pat-tuple-5.stderr
index 31ea3a17871..307ad711b74 100644
--- a/src/test/ui/half-open-range-patterns/pat-tuple-5.stderr
+++ b/src/test/ui/half-open-range-patterns/pat-tuple-5.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/pat-tuple-5.rs:8:10
    |
+LL |     match (0, 1) {
+   |           ------ this expression has type `({integer}, {integer})`
 LL |         (PAT ..) => {}
    |          ^^^ expected tuple, found `u8`
    |
diff --git a/src/test/ui/issues/issue-11844.stderr b/src/test/ui/issues/issue-11844.stderr
index ecab1074a29..9d7470e7af9 100644
--- a/src/test/ui/issues/issue-11844.stderr
+++ b/src/test/ui/issues/issue-11844.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/issue-11844.rs:6:9
    |
+LL |     match a {
+   |           - this expression has type `Option<Box<{integer}>>`
 LL |         Ok(a) =>
    |         ^^^^^ expected enum `Option`, found enum `Result`
    |
diff --git a/src/test/ui/issues/issue-12552.stderr b/src/test/ui/issues/issue-12552.stderr
index 1ba6852b17c..3d8852ca748 100644
--- a/src/test/ui/issues/issue-12552.stderr
+++ b/src/test/ui/issues/issue-12552.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/issue-12552.rs:6:5
    |
+LL |   match t {
+   |         - this expression has type `Result<_, {integer}>`
 LL |     Some(k) => match k {
    |     ^^^^^^^ expected enum `Result`, found enum `Option`
    |
@@ -10,6 +12,9 @@ LL |     Some(k) => match k {
 error[E0308]: mismatched types
   --> $DIR/issue-12552.rs:9:5
    |
+LL |   match t {
+   |         - this expression has type `Result<_, {integer}>`
+...
 LL |     None => ()
    |     ^^^^ expected enum `Result`, found enum `Option`
    |
diff --git a/src/test/ui/issues/issue-13466.stderr b/src/test/ui/issues/issue-13466.stderr
index 15ee49a5fdd..c78466f4e8c 100644
--- a/src/test/ui/issues/issue-13466.stderr
+++ b/src/test/ui/issues/issue-13466.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/issue-13466.rs:8:9
    |
+LL |     let _x: usize = match Some(1) {
+   |                           ------- this expression has type `Option<{integer}>`
 LL |         Ok(u) => u,
    |         ^^^^^ expected enum `Option`, found enum `Result`
    |
@@ -10,6 +12,9 @@ LL |         Ok(u) => u,
 error[E0308]: mismatched types
   --> $DIR/issue-13466.rs:14:9
    |
+LL |     let _x: usize = match Some(1) {
+   |                           ------- this expression has type `Option<{integer}>`
+...
 LL |         Err(e) => panic!(e)
    |         ^^^^^^ expected enum `Option`, found enum `Result`
    |
diff --git a/src/test/ui/issues/issue-33504.stderr b/src/test/ui/issues/issue-33504.stderr
index 1e61178f42e..ec15525ed06 100644
--- a/src/test/ui/issues/issue-33504.stderr
+++ b/src/test/ui/issues/issue-33504.stderr
@@ -5,7 +5,7 @@ LL | struct Test;
    | ------------ unit struct defined here
 ...
 LL |         let Test = 1;
-   |             ^^^^
+   |             ^^^^   - this expression has type `{integer}`
    |             |
    |             expected integer, found struct `Test`
    |             `Test` is interpreted as a unit struct, not a new binding
diff --git a/src/test/ui/issues/issue-3680.stderr b/src/test/ui/issues/issue-3680.stderr
index 8dc0dfa2356..e8fafa76b91 100644
--- a/src/test/ui/issues/issue-3680.stderr
+++ b/src/test/ui/issues/issue-3680.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/issue-3680.rs:3:9
    |
+LL |     match None {
+   |           ---- this expression has type `Option<_>`
 LL |         Err(_) => ()
    |         ^^^^^^ expected enum `Option`, found enum `Result`
    |
diff --git a/src/test/ui/issues/issue-4968.stderr b/src/test/ui/issues/issue-4968.stderr
index 5451cf42355..57ff7fe09e5 100644
--- a/src/test/ui/issues/issue-4968.stderr
+++ b/src/test/ui/issues/issue-4968.stderr
@@ -5,11 +5,12 @@ LL | const A: (isize,isize) = (4,2);
    | ------------------------------- constant defined here
 LL | fn main() {
 LL |     match 42 { A => () }
-   |                ^
-   |                |
-   |                expected integer, found tuple
-   |                `A` is interpreted as a constant, not a new binding
-   |                help: introduce a new binding instead: `other_a`
+   |           --   ^
+   |           |    |
+   |           |    expected integer, found tuple
+   |           |    `A` is interpreted as a constant, not a new binding
+   |           |    help: introduce a new binding instead: `other_a`
+   |           this expression has type `{integer}`
    |
    = note: expected type `{integer}`
              found tuple `(isize, isize)`
diff --git a/src/test/ui/issues/issue-66706.stderr b/src/test/ui/issues/issue-66706.stderr
index 3e933a0f01b..e8cb18f5c1e 100644
--- a/src/test/ui/issues/issue-66706.stderr
+++ b/src/test/ui/issues/issue-66706.stderr
@@ -36,7 +36,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-66706.rs:2:5
    |
 LL | fn a() {
-   |        - possibly return type missing here?
+   |        - help: try adding a return type: `-> [i32; _]`
 LL |     [0; [|_: _ &_| ()].len()]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found array `[{integer}; _]`
 
@@ -44,7 +44,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-66706.rs:14:5
    |
 LL | fn c() {
-   |        - possibly return type missing here?
+   |        - help: try adding a return type: `-> [i32; _]`
 LL |     [0; [|&_: _ &_| {}; 0 ].len()]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found array `[{integer}; _]`
 
@@ -52,7 +52,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-66706.rs:20:5
    |
 LL | fn d() {
-   |        - possibly return type missing here?
+   |        - help: try adding a return type: `-> [i32; _]`
 LL |     [0; match [|f @ &ref _| () ] {} ]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found array `[{integer}; _]`
 
diff --git a/src/test/ui/issues/issue-72574-1.stderr b/src/test/ui/issues/issue-72574-1.stderr
index 5d3d390a95d..653869a237d 100644
--- a/src/test/ui/issues/issue-72574-1.stderr
+++ b/src/test/ui/issues/issue-72574-1.stderr
@@ -21,6 +21,8 @@ LL |         (_a, _x @ ..) => {}
 error[E0308]: mismatched types
   --> $DIR/issue-72574-1.rs:4:9
    |
+LL |     match x {
+   |           - this expression has type `({integer}, {integer}, {integer})`
 LL |         (_a, _x @ ..) => {}
    |         ^^^^^^^^^^^^^ expected a tuple with 3 elements, found one with 2 elements
    |
diff --git a/src/test/ui/keyword/keyword-false-as-identifier.stderr b/src/test/ui/keyword/keyword-false-as-identifier.stderr
index fcc30064018..6dcfa3a4811 100644
--- a/src/test/ui/keyword/keyword-false-as-identifier.stderr
+++ b/src/test/ui/keyword/keyword-false-as-identifier.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/keyword-false-as-identifier.rs:2:9
    |
 LL |     let false = 22;
-   |         ^^^^^ expected integer, found `bool`
+   |         ^^^^^   -- this expression has type `{integer}`
+   |         |
+   |         expected integer, found `bool`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/keyword/keyword-true-as-identifier.stderr b/src/test/ui/keyword/keyword-true-as-identifier.stderr
index b8cc2ffd2a8..86f6e00064f 100644
--- a/src/test/ui/keyword/keyword-true-as-identifier.stderr
+++ b/src/test/ui/keyword/keyword-true-as-identifier.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/keyword-true-as-identifier.rs:2:9
    |
 LL |     let true = 22;
-   |         ^^^^ expected integer, found `bool`
+   |         ^^^^   -- this expression has type `{integer}`
+   |         |
+   |         expected integer, found `bool`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/match/match-range-fail.stderr b/src/test/ui/match/match-range-fail.stderr
index 938c05ac732..65db92df19f 100644
--- a/src/test/ui/match/match-range-fail.stderr
+++ b/src/test/ui/match/match-range-fail.stderr
@@ -27,6 +27,8 @@ LL |         true ..= "what" => {}
 error[E0308]: mismatched types
   --> $DIR/match-range-fail.rs:18:9
    |
+LL |     match 5 {
+   |           - this expression has type `{integer}`
 LL |         'c' ..= 100 => { }
    |         ^^^     --- this is of type `{integer}`
    |         |
diff --git a/src/test/ui/mismatched_types/E0409.stderr b/src/test/ui/mismatched_types/E0409.stderr
index eb884bcc622..ef03b67b1b0 100644
--- a/src/test/ui/mismatched_types/E0409.stderr
+++ b/src/test/ui/mismatched_types/E0409.stderr
@@ -9,6 +9,8 @@ LL |         (0, ref y) | (y, 0) => {}
 error[E0308]: mismatched types
   --> $DIR/E0409.rs:5:23
    |
+LL |     match x {
+   |           - this expression has type `({integer}, {integer})`
 LL |         (0, ref y) | (y, 0) => {}
    |             -----     ^ expected `&{integer}`, found integer
    |             |
diff --git a/src/test/ui/mut/mut-pattern-mismatched.stderr b/src/test/ui/mut/mut-pattern-mismatched.stderr
index ccc8ac1278c..cad1cef5155 100644
--- a/src/test/ui/mut/mut-pattern-mismatched.stderr
+++ b/src/test/ui/mut/mut-pattern-mismatched.stderr
@@ -3,6 +3,9 @@ error[E0308]: mismatched types
    |
 LL |      let &_
    |          ^^ types differ in mutability
+...
+LL |         = foo;
+   |           --- this expression has type `&mut {integer}`
    |
    = note: expected mutable reference `&mut {integer}`
                       found reference `&_`
@@ -12,6 +15,9 @@ error[E0308]: mismatched types
    |
 LL |     let &mut _
    |         ^^^^^^ types differ in mutability
+...
+LL |          = bar;
+   |            --- this expression has type `&{integer}`
    |
    = note:      expected reference `&{integer}`
            found mutable reference `&mut _`
diff --git a/src/test/ui/never_type/diverging-tuple-parts-39485.stderr b/src/test/ui/never_type/diverging-tuple-parts-39485.stderr
index e99a38aaaee..4b5b8c45d59 100644
--- a/src/test/ui/never_type/diverging-tuple-parts-39485.stderr
+++ b/src/test/ui/never_type/diverging-tuple-parts-39485.stderr
@@ -1,13 +1,15 @@
 error[E0308]: mismatched types
   --> $DIR/diverging-tuple-parts-39485.rs:8:5
    |
-LL | fn g() {
-   |        - possibly return type missing here?
 LL |     &panic!()
    |     ^^^^^^^^^ expected `()`, found reference
    |
    = note: expected unit type `()`
               found reference `&_`
+help: a return type might be missing here
+   |
+LL | fn g() -> _ {
+   |        ++++
 help: consider removing the borrow
    |
 LL -     &panic!()
diff --git a/src/test/ui/or-patterns/already-bound-name.stderr b/src/test/ui/or-patterns/already-bound-name.stderr
index 92416a0d5cb..66112165622 100644
--- a/src/test/ui/or-patterns/already-bound-name.stderr
+++ b/src/test/ui/or-patterns/already-bound-name.stderr
@@ -86,8 +86,9 @@ error[E0308]: mismatched types
   --> $DIR/already-bound-name.rs:30:32
    |
 LL |     let (B(A(a, _) | B(a)) | A(a, A(a, _) | B(a))) = B(B(1));
-   |              -                 ^ expected integer, found enum `E`
-   |              |
+   |              -                 ^                     ------- this expression has type `E<E<{integer}>>`
+   |              |                 |
+   |              |                 expected integer, found enum `E`
    |              first introduced with type `{integer}` here
    |
    = note: expected type `{integer}`
diff --git a/src/test/ui/or-patterns/inconsistent-modes.stderr b/src/test/ui/or-patterns/inconsistent-modes.stderr
index 95e8618808c..dae6bb41e74 100644
--- a/src/test/ui/or-patterns/inconsistent-modes.stderr
+++ b/src/test/ui/or-patterns/inconsistent-modes.stderr
@@ -65,8 +65,9 @@ error[E0308]: mismatched types
   --> $DIR/inconsistent-modes.rs:13:32
    |
 LL |     let (Ok((ref a, b)) | Err((ref mut a, ref b))) = Ok((0, &0));
-   |              -----             ^^^^^^^^^ types differ in mutability
-   |              |
+   |              -----             ^^^^^^^^^             ----------- this expression has type `Result<({integer}, &{integer}), (_, _)>`
+   |              |                 |
+   |              |                 types differ in mutability
    |              first introduced with type `&{integer}` here
    |
    = note: expected type `&{integer}`
diff --git a/src/test/ui/parser/recover-range-pats.stderr b/src/test/ui/parser/recover-range-pats.stderr
index 9296ad2e335..8063ba8e9f7 100644
--- a/src/test/ui/parser/recover-range-pats.stderr
+++ b/src/test/ui/parser/recover-range-pats.stderr
@@ -303,8 +303,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-range-pats.rs:22:12
    |
 LL |     if let .0..Y = 0 {}
-   |            ^^  - this is of type `u8`
-   |            |
+   |            ^^  -   - this expression has type `{integer}`
+   |            |   |
+   |            |   this is of type `u8`
    |            expected integer, found floating-point number
 
 error[E0308]: mismatched types
@@ -336,8 +337,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-range-pats.rs:35:12
    |
 LL |     if let .0..=Y = 0 {}
-   |            ^^   - this is of type `u8`
-   |            |
+   |            ^^   -   - this expression has type `{integer}`
+   |            |    |
+   |            |    this is of type `u8`
    |            expected integer, found floating-point number
 
 error[E0308]: mismatched types
@@ -369,8 +371,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-range-pats.rs:60:12
    |
 LL |     if let .0...Y = 0 {}
-   |            ^^   - this is of type `u8`
-   |            |
+   |            ^^   -   - this expression has type `{integer}`
+   |            |    |
+   |            |    this is of type `u8`
    |            expected integer, found floating-point number
 
 error[E0308]: mismatched types
@@ -392,7 +395,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-range-pats.rs:75:12
    |
 LL |     if let .0.. = 0 {}
-   |            ^^ expected integer, found floating-point number
+   |            ^^     - this expression has type `{integer}`
+   |            |
+   |            expected integer, found floating-point number
 
 error[E0029]: only `char` and numeric types are allowed in range patterns
   --> $DIR/recover-range-pats.rs:83:12
@@ -404,7 +409,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-range-pats.rs:85:12
    |
 LL |     if let .0..= = 0 {}
-   |            ^^ expected integer, found floating-point number
+   |            ^^      - this expression has type `{integer}`
+   |            |
+   |            expected integer, found floating-point number
 
 error[E0029]: only `char` and numeric types are allowed in range patterns
   --> $DIR/recover-range-pats.rs:93:12
@@ -416,7 +423,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-range-pats.rs:95:12
    |
 LL |     if let .0... = 0 {}
-   |            ^^ expected integer, found floating-point number
+   |            ^^      - this expression has type `{integer}`
+   |            |
+   |            expected integer, found floating-point number
 
 error[E0029]: only `char` and numeric types are allowed in range patterns
   --> $DIR/recover-range-pats.rs:103:14
@@ -428,7 +437,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-range-pats.rs:105:15
    |
 LL |     if let .. .0 = 0 {}
-   |               ^^ expected integer, found floating-point number
+   |               ^^   - this expression has type `{integer}`
+   |               |
+   |               expected integer, found floating-point number
 
 error[E0029]: only `char` and numeric types are allowed in range patterns
   --> $DIR/recover-range-pats.rs:113:15
@@ -440,7 +451,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-range-pats.rs:115:15
    |
 LL |     if let ..=.0 = 0 {}
-   |               ^^ expected integer, found floating-point number
+   |               ^^   - this expression has type `{integer}`
+   |               |
+   |               expected integer, found floating-point number
 
 error[E0029]: only `char` and numeric types are allowed in range patterns
   --> $DIR/recover-range-pats.rs:125:15
@@ -452,7 +465,9 @@ error[E0308]: mismatched types
   --> $DIR/recover-range-pats.rs:128:15
    |
 LL |     if let ....3 = 0 {}
-   |               ^^ expected integer, found floating-point number
+   |               ^^   - this expression has type `{integer}`
+   |               |
+   |               expected integer, found floating-point number
 
 error: aborting due to 60 previous errors
 
diff --git a/src/test/ui/pattern/issue-74702.stderr b/src/test/ui/pattern/issue-74702.stderr
index 53dcf97f81c..f2e2c8f021b 100644
--- a/src/test/ui/pattern/issue-74702.stderr
+++ b/src/test/ui/pattern/issue-74702.stderr
@@ -22,7 +22,9 @@ error[E0308]: mismatched types
   --> $DIR/issue-74702.rs:2:9
    |
 LL |     let (foo @ ..,) = (0, 0);
-   |         ^^^^^^^^^^^ expected a tuple with 2 elements, found one with 1 element
+   |         ^^^^^^^^^^^   ------ this expression has type `({integer}, {integer})`
+   |         |
+   |         expected a tuple with 2 elements, found one with 1 element
    |
    = note: expected tuple `({integer}, {integer})`
               found tuple `(_,)`
diff --git a/src/test/ui/pattern/pat-tuple-overfield.stderr b/src/test/ui/pattern/pat-tuple-overfield.stderr
index 64b6e5eec55..1c44f7e5f6f 100644
--- a/src/test/ui/pattern/pat-tuple-overfield.stderr
+++ b/src/test/ui/pattern/pat-tuple-overfield.stderr
@@ -150,6 +150,8 @@ LL |         E1::Z0 => {}
 error[E0308]: mismatched types
   --> $DIR/pat-tuple-overfield.rs:19:9
    |
+LL |     match (1, 2, 3) {
+   |           --------- this expression has type `({integer}, {integer}, {integer})`
 LL |         (1, 2, 3, 4) => {}
    |         ^^^^^^^^^^^^ expected a tuple with 3 elements, found one with 4 elements
    |
@@ -159,6 +161,9 @@ LL |         (1, 2, 3, 4) => {}
 error[E0308]: mismatched types
   --> $DIR/pat-tuple-overfield.rs:20:9
    |
+LL |     match (1, 2, 3) {
+   |           --------- this expression has type `({integer}, {integer}, {integer})`
+LL |         (1, 2, 3, 4) => {}
 LL |         (1, 2, .., 3, 4) => {}
    |         ^^^^^^^^^^^^^^^^ expected a tuple with 3 elements, found one with 4 elements
    |
diff --git a/src/test/ui/proc-macro/span-preservation.stderr b/src/test/ui/proc-macro/span-preservation.stderr
index e9a44ccb12e..66c68be2f09 100644
--- a/src/test/ui/proc-macro/span-preservation.stderr
+++ b/src/test/ui/proc-macro/span-preservation.stderr
@@ -38,7 +38,7 @@ error[E0308]: mismatched types
   --> $DIR/span-preservation.rs:39:5
    |
 LL | extern "C" fn bar() {
-   |                     - possibly return type missing here?
+   |                     - help: try adding a return type: `-> i32`
 LL |     0
    |     ^ expected `()`, found integer
 
@@ -46,7 +46,7 @@ error[E0308]: mismatched types
   --> $DIR/span-preservation.rs:44:5
    |
 LL | extern "C" fn baz() {
-   |                     - possibly return type missing here?
+   |                     - help: try adding a return type: `-> i32`
 LL |     0
    |     ^ expected `()`, found integer
 
@@ -54,7 +54,7 @@ error[E0308]: mismatched types
   --> $DIR/span-preservation.rs:49:5
    |
 LL | extern "Rust" fn rust_abi() {
-   |                             - possibly return type missing here?
+   |                             - help: try adding a return type: `-> i32`
 LL |     0
    |     ^ expected `()`, found integer
 
@@ -62,7 +62,7 @@ error[E0308]: mismatched types
   --> $DIR/span-preservation.rs:54:5
    |
 LL | extern "\x43" fn c_abi_escaped() {
-   |                                  - possibly return type missing here?
+   |                                  - help: try adding a return type: `-> i32`
 LL |     0
    |     ^ expected `()`, found integer
 
diff --git a/src/test/ui/return/return-type.stderr b/src/test/ui/return/return-type.stderr
index f86209a651d..5af136e6011 100644
--- a/src/test/ui/return/return-type.stderr
+++ b/src/test/ui/return/return-type.stderr
@@ -1,15 +1,19 @@
 error[E0308]: mismatched types
   --> $DIR/return-type.rs:10:5
    |
-LL | fn bar() {
-   |          - possibly return type missing here?
 LL |     foo(4 as usize)
-   |     ^^^^^^^^^^^^^^^- help: consider using a semicolon here: `;`
-   |     |
-   |     expected `()`, found struct `S`
+   |     ^^^^^^^^^^^^^^^ expected `()`, found struct `S`
    |
    = note: expected unit type `()`
                  found struct `S<usize>`
+help: consider using a semicolon here
+   |
+LL |     foo(4 as usize);
+   |                    +
+help: try adding a return type
+   |
+LL | fn bar() -> S<usize> {
+   |          +++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/slightly-nice-generic-literal-messages.stderr b/src/test/ui/slightly-nice-generic-literal-messages.stderr
index 61eabed9504..14f01f0ebdf 100644
--- a/src/test/ui/slightly-nice-generic-literal-messages.stderr
+++ b/src/test/ui/slightly-nice-generic-literal-messages.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/slightly-nice-generic-literal-messages.rs:7:9
    |
+LL |     match Foo(1.1, marker::PhantomData) {
+   |           ----------------------------- this expression has type `Foo<{float}, _>`
 LL |         1 => {}
    |         ^ expected struct `Foo`, found integer
    |
diff --git a/src/test/ui/structs/structure-constructor-type-mismatch.stderr b/src/test/ui/structs/structure-constructor-type-mismatch.stderr
index 98972a12159..3d64fc601df 100644
--- a/src/test/ui/structs/structure-constructor-type-mismatch.stderr
+++ b/src/test/ui/structs/structure-constructor-type-mismatch.stderr
@@ -101,6 +101,8 @@ LL | type PointF = Point<f32>;
 error[E0308]: mismatched types
   --> $DIR/structure-constructor-type-mismatch.rs:54:9
    |
+LL |     match (Point { x: 1, y: 2 }) {
+   |           ---------------------- this expression has type `Point<{integer}>`
 LL |         PointF::<u32> { .. } => {}
    |         ^^^^^^^^^^^^^^^^^^^^ expected integer, found `f32`
    |
@@ -110,6 +112,8 @@ LL |         PointF::<u32> { .. } => {}
 error[E0308]: mismatched types
   --> $DIR/structure-constructor-type-mismatch.rs:59:9
    |
+LL |     match (Point { x: 1, y: 2 }) {
+   |           ---------------------- this expression has type `Point<{integer}>`
 LL |         PointF { .. } => {}
    |         ^^^^^^^^^^^^^ expected integer, found `f32`
    |
@@ -119,6 +123,8 @@ LL |         PointF { .. } => {}
 error[E0308]: mismatched types
   --> $DIR/structure-constructor-type-mismatch.rs:67:9
    |
+LL |     match (Pair { x: 1, y: 2 }) {
+   |           --------------------- this expression has type `Pair<{integer}, {integer}>`
 LL |         PairF::<u32> { .. } => {}
    |         ^^^^^^^^^^^^^^^^^^^ expected integer, found `f32`
    |
diff --git a/src/test/ui/typeck/issue-91334.stderr b/src/test/ui/typeck/issue-91334.stderr
index 0872e83ea2e..633c7b11aa2 100644
--- a/src/test/ui/typeck/issue-91334.stderr
+++ b/src/test/ui/typeck/issue-91334.stderr
@@ -40,7 +40,7 @@ error[E0308]: mismatched types
 LL | fn f(){||yield(((){),
    |       -^^^^^^^^^^^^^^^ expected `()`, found generator
    |       |
-   |       possibly return type missing here?
+   |       help: a return type might be missing here: `-> _`
    |
    = note: expected unit type `()`
               found generator `[generator@$DIR/issue-91334.rs:10:8: 10:23]`
diff --git a/src/test/ui/typeck/return_type_containing_closure.rs b/src/test/ui/typeck/return_type_containing_closure.rs
index aee9769b280..29624e08a2e 100644
--- a/src/test/ui/typeck/return_type_containing_closure.rs
+++ b/src/test/ui/typeck/return_type_containing_closure.rs
@@ -1,10 +1,10 @@
 #[allow(unused)]
-fn foo() {
-    //~^ NOTE possibly return type missing here?
+fn foo() { //~ HELP a return type might be missing here
     vec!['a'].iter().map(|c| c)
     //~^ ERROR mismatched types [E0308]
     //~| NOTE expected `()`, found struct `Map`
     //~| NOTE expected unit type `()`
+    //~| HELP consider using a semicolon here
 }
 
 fn main() {}
diff --git a/src/test/ui/typeck/return_type_containing_closure.stderr b/src/test/ui/typeck/return_type_containing_closure.stderr
index b08152d6331..ae72b1477c8 100644
--- a/src/test/ui/typeck/return_type_containing_closure.stderr
+++ b/src/test/ui/typeck/return_type_containing_closure.stderr
@@ -1,16 +1,19 @@
 error[E0308]: mismatched types
-  --> $DIR/return_type_containing_closure.rs:4:5
+  --> $DIR/return_type_containing_closure.rs:3:5
    |
-LL | fn foo() {
-   |          - possibly return type missing here?
-LL |
 LL |     vec!['a'].iter().map(|c| c)
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^- help: consider using a semicolon here: `;`
-   |     |
-   |     expected `()`, found struct `Map`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found struct `Map`
    |
    = note: expected unit type `()`
-                 found struct `Map<std::slice::Iter<'_, char>, [closure@$DIR/return_type_containing_closure.rs:4:26: 4:31]>`
+                 found struct `Map<std::slice::Iter<'_, char>, [closure@$DIR/return_type_containing_closure.rs:3:26: 3:31]>`
+help: consider using a semicolon here
+   |
+LL |     vec!['a'].iter().map(|c| c);
+   |                                +
+help: a return type might be missing here
+   |
+LL | fn foo() -> _ {
+   |          ++++
 
 error: aborting due to previous error