Rollup merge of #69452 - Centril:typeck-pat, r=estebank

typeck: use `Pattern` obligation cause more for better diagnostics

r? @estebank

25 files changed, 222 insertions, 67 deletions

diff --git a/src/test/ui/destructure-trait-ref.stderr b/src/test/ui/destructure-trait-ref.stderr
index f99bf2ffdc9..1382cf643a1 100644
--- a/src/test/ui/destructure-trait-ref.stderr
+++ b/src/test/ui/destructure-trait-ref.stderr
@@ -20,7 +20,7 @@ error[E0308]: mismatched types
   --> $DIR/destructure-trait-ref.rs:32:10
    |
 LL |     let &&x = &1isize as &dyn T;
-   |          ^^
+   |          ^^   ----------------- this expression has type `&dyn T`
    |          |
    |          expected trait object `dyn T`, found reference
    |          help: you can probably remove the explicit borrow: `x`
@@ -32,7 +32,7 @@ error[E0308]: mismatched types
   --> $DIR/destructure-trait-ref.rs:36:11
    |
 LL |     let &&&x = &(&1isize as &dyn T);
-   |           ^^
+   |           ^^   -------------------- this expression has type `&&dyn T`
    |           |
    |           expected trait object `dyn T`, found reference
    |           help: you can probably remove the explicit borrow: `x`
diff --git a/src/test/ui/elide-errors-on-mismatched-tuple.stderr b/src/test/ui/elide-errors-on-mismatched-tuple.stderr
index 122c71bebc4..e0537ff6faa 100644
--- a/src/test/ui/elide-errors-on-mismatched-tuple.stderr
+++ b/src/test/ui/elide-errors-on-mismatched-tuple.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/elide-errors-on-mismatched-tuple.rs:14:9
    |
 LL |     let (a, b, c) = (A::new(), A::new()); // This tuple is 2 elements, should be three
-   |         ^^^^^^^^^ expected a tuple with 2 elements, found one with 3 elements
+   |         ^^^^^^^^^   -------------------- this expression has type `(A, A)`
+   |         |
+   |         expected a tuple with 2 elements, found one with 3 elements
    |
    = note: expected tuple `(A, A)`
               found tuple `(_, _, _)`
diff --git a/src/test/ui/issues/issue-12552.stderr b/src/test/ui/issues/issue-12552.stderr
index 60c4cceac51..45fede44106 100644
--- a/src/test/ui/issues/issue-12552.stderr
+++ b/src/test/ui/issues/issue-12552.stderr
@@ -12,6 +12,9 @@ LL |     Some(k) => match k {
 error[E0308]: mismatched types
   --> $DIR/issue-12552.rs:9:5
    |
+LL |   match t {
+   |         - this expression has type `std::result::Result<_, {integer}>`
+...
 LL |     None => ()
    |     ^^^^ expected enum `std::result::Result`, found enum `std::option::Option`
    |
diff --git a/src/test/ui/issues/issue-37026.stderr b/src/test/ui/issues/issue-37026.stderr
index 361369e68bc..f0285730c5a 100644
--- a/src/test/ui/issues/issue-37026.stderr
+++ b/src/test/ui/issues/issue-37026.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/issue-37026.rs:6:9
    |
 LL |     let empty_struct::XEmpty2 = ();
-   |         ^^^^^^^^^^^^^^^^^^^^^ expected `()`, found struct `empty_struct::XEmpty2`
+   |         ^^^^^^^^^^^^^^^^^^^^^   -- this expression has type `()`
+   |         |
+   |         expected `()`, found struct `empty_struct::XEmpty2`
 
 error[E0308]: mismatched types
   --> $DIR/issue-37026.rs:7:9
diff --git a/src/test/ui/issues/issue-5100.stderr b/src/test/ui/issues/issue-5100.stderr
index c47e8689436..c81d6dcaf02 100644
--- a/src/test/ui/issues/issue-5100.stderr
+++ b/src/test/ui/issues/issue-5100.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/issue-5100.rs:8:9
    |
+LL |     match (true, false) {
+   |           ------------- this expression has type `(bool, bool)`
 LL |         A::B => (),
    |         ^^^^ expected tuple, found enum `A`
    |
@@ -10,6 +12,8 @@ LL |         A::B => (),
 error[E0308]: mismatched types
   --> $DIR/issue-5100.rs:17:9
    |
+LL |     match (true, false) {
+   |           ------------- this expression has type `(bool, bool)`
 LL |         (true, false, false) => ()
    |         ^^^^^^^^^^^^^^^^^^^^ expected a tuple with 2 elements, found one with 3 elements
    |
@@ -19,6 +23,8 @@ LL |         (true, false, false) => ()
 error[E0308]: mismatched types
   --> $DIR/issue-5100.rs:25:9
    |
+LL |     match (true, false) {
+   |           ------------- this expression has type `(bool, bool)`
 LL |         (true, false, false) => ()
    |         ^^^^^^^^^^^^^^^^^^^^ expected a tuple with 2 elements, found one with 3 elements
    |
@@ -39,6 +45,8 @@ LL |         box (true, false) => ()
 error[E0308]: mismatched types
   --> $DIR/issue-5100.rs:40:9
    |
+LL |     match (true, false) {
+   |           ------------- this expression has type `(bool, bool)`
 LL |         &(true, false) => ()
    |         ^^^^^^^^^^^^^^ expected tuple, found reference
    |
diff --git a/src/test/ui/issues/issue-7867.stderr b/src/test/ui/issues/issue-7867.stderr
index 58e82facf80..4a29464aebd 100644
--- a/src/test/ui/issues/issue-7867.stderr
+++ b/src/test/ui/issues/issue-7867.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/issue-7867.rs:7:9
    |
+LL |     match (true, false) {
+   |           ------------- this expression has type `(bool, bool)`
 LL |         A::B => (),
    |         ^^^^ expected tuple, found enum `A`
    |
diff --git a/src/test/ui/match/match-ill-type2.stderr b/src/test/ui/match/match-ill-type2.stderr
index 1cf61ebad43..5078f03d601 100644
--- a/src/test/ui/match/match-ill-type2.stderr
+++ b/src/test/ui/match/match-ill-type2.stderr
@@ -1,6 +1,9 @@
 error[E0308]: mismatched types
   --> $DIR/match-ill-type2.rs:4:9
    |
+LL |     match 1i32 {
+   |           ---- this expression has type `i32`
+LL |         1i32 => 1,
 LL |         2u32 => 1,
    |         ^^^^ expected `i32`, found `u32`
 
diff --git a/src/test/ui/match/match-tag-nullary.stderr b/src/test/ui/match/match-tag-nullary.stderr
index 4b6260b2199..3703a59edb8 100644
--- a/src/test/ui/match/match-tag-nullary.stderr
+++ b/src/test/ui/match/match-tag-nullary.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/match-tag-nullary.rs:4:40
    |
 LL | fn main() { let x: A = A::A; match x { B::B => { } } }
-   |                                        ^^^^ expected enum `A`, found enum `B`
+   |                                    -   ^^^^ expected enum `A`, found enum `B`
+   |                                    |
+   |                                    this expression has type `A`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/mismatched_types/E0409.stderr b/src/test/ui/mismatched_types/E0409.stderr
index 2306fb35273..f5c8b02ae27 100644
--- a/src/test/ui/mismatched_types/E0409.stderr
+++ b/src/test/ui/mismatched_types/E0409.stderr
@@ -12,7 +12,11 @@ error[E0308]: mismatched types
 LL |     match x {
    |           - this expression has type `({integer}, {integer})`
 LL |         (0, ref y) | (y, 0) => {}
-   |                       ^ expected `&{integer}`, found integer
+   |             -----     ^ expected `&{integer}`, found integer
+   |             |
+   |             first introduced with type `&{integer}` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/mismatched_types/issue-38371.stderr b/src/test/ui/mismatched_types/issue-38371.stderr
index 802a2fef6bd..c2bce305877 100644
--- a/src/test/ui/mismatched_types/issue-38371.stderr
+++ b/src/test/ui/mismatched_types/issue-38371.stderr
@@ -3,7 +3,8 @@ error[E0308]: mismatched types
    |
 LL | fn foo(&foo: Foo) {
    |        ^^^^------
-   |        |
+   |        |     |
+   |        |     expected due to this
    |        expected struct `Foo`, found reference
    |        help: did you mean `foo`: `&Foo`
    |
@@ -14,7 +15,7 @@ error[E0308]: mismatched types
   --> $DIR/issue-38371.rs:18:9
    |
 LL | fn agh(&&bar: &u32) {
-   |         ^^^^
+   |         ^^^^  ---- expected due to this
    |         |
    |         expected `u32`, found reference
    |         help: you can probably remove the explicit borrow: `bar`
@@ -26,7 +27,9 @@ error[E0308]: mismatched types
   --> $DIR/issue-38371.rs:21:8
    |
 LL | fn bgh(&&bar: u32) {
-   |        ^^^^^ expected `u32`, found reference
+   |        ^^^^^  --- expected due to this
+   |        |
+   |        expected `u32`, found reference
    |
    = note:   expected type `u32`
            found reference `&_`
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/or-patterns/already-bound-name.stderr b/src/test/ui/or-patterns/already-bound-name.stderr
index 9924b0d7f72..97933ca1229 100644
--- a/src/test/ui/or-patterns/already-bound-name.stderr
+++ b/src/test/ui/or-patterns/already-bound-name.stderr
@@ -86,12 +86,14 @@ error[E0308]: mismatched types
   --> $DIR/already-bound-name.rs:32:31
    |
 LL |     let B(A(a, _) | B(a)) | A(a, A(a, _) | B(a)) = B(B(1));
-   |                               ^                    ------- this expression has type `E<E<{integer}>>`
-   |                               |
-   |                               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}`
               found type `E<{integer}>`
+   = note: a binding must have the same type in all alternatives
 
 error: aborting due to 15 previous errors
 
diff --git a/src/test/ui/or-patterns/inconsistent-modes.stderr b/src/test/ui/or-patterns/inconsistent-modes.stderr
index c329f905960..8c01e00bae3 100644
--- a/src/test/ui/or-patterns/inconsistent-modes.stderr
+++ b/src/test/ui/or-patterns/inconsistent-modes.stderr
@@ -52,23 +52,27 @@ error[E0308]: mismatched types
   --> $DIR/inconsistent-modes.rs:11:25
    |
 LL |     let Ok(ref a) | Err(ref mut a): Result<&u8, &mut u8> = Ok(&0);
-   |                         ^^^^^^^^^   -------------------- expected due to this
-   |                         |
-   |                         types differ in mutability
+   |            -----        ^^^^^^^^^   -------------------- expected due to this
+   |            |            |
+   |            |            types differ in mutability
+   |            first introduced with type `&&u8` here
    |
    = note: expected type `&&u8`
               found type `&mut &mut u8`
+   = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/inconsistent-modes.rs:14:31
    |
 LL |     let Ok((ref a, b)) | Err((ref mut a, ref b)) = Ok((0, &0));
-   |                               ^^^^^^^^^            ----------- this expression has type `std::result::Result<({integer}, &{integer}), (_, _)>`
-   |                               |
-   |                               types differ in mutability
+   |             -----             ^^^^^^^^^            ----------- this expression has type `std::result::Result<({integer}, &{integer}), (_, _)>`
+   |             |                 |
+   |             |                 types differ in mutability
+   |             first introduced with type `&{integer}` here
    |
    = note: expected type `&{integer}`
               found type `&mut _`
+   = note: a binding must have the same type in all alternatives
 
 error: aborting due to 9 previous errors
 
diff --git a/src/test/ui/or-patterns/or-patterns-binding-type-mismatch.stderr b/src/test/ui/or-patterns/or-patterns-binding-type-mismatch.stderr
index 5094f04b920..d5e029d668d 100644
--- a/src/test/ui/or-patterns/or-patterns-binding-type-mismatch.stderr
+++ b/src/test/ui/or-patterns/or-patterns-binding-type-mismatch.stderr
@@ -4,7 +4,11 @@ error[E0308]: mismatched types
 LL |     match Blah::A(1, 1, 2) {
    |           ---------------- this expression has type `main::Blah`
 LL |         Blah::A(_, x, y) | Blah::B(x, y) => {}
-   |                                       ^ expected `usize`, found `isize`
+   |                       -               ^ expected `usize`, found `isize`
+   |                       |
+   |                       first introduced with type `usize` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:17:44
@@ -12,7 +16,11 @@ error[E0308]: mismatched types
 LL |     match Some(Blah::A(1, 1, 2)) {
    |           ---------------------- this expression has type `std::option::Option<main::Blah>`
 LL |         Some(Blah::A(_, x, y) | Blah::B(x, y)) => {}
-   |                                            ^ expected `usize`, found `isize`
+   |                            -               ^ expected `usize`, found `isize`
+   |                            |
+   |                            first introduced with type `usize` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:21:19
@@ -20,7 +28,11 @@ error[E0308]: mismatched types
 LL |     match (0u8, 1u16) {
    |           ----------- this expression has type `(u8, u16)`
 LL |         (x, y) | (y, x) => {}
-   |                   ^ expected `u16`, found `u8`
+   |             -     ^ expected `u16`, found `u8`
+   |             |
+   |             first introduced with type `u16` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:21:22
@@ -28,7 +40,11 @@ error[E0308]: mismatched types
 LL |     match (0u8, 1u16) {
    |           ----------- this expression has type `(u8, u16)`
 LL |         (x, y) | (y, x) => {}
-   |                      ^ expected `u8`, found `u16`
+   |          -           ^ expected `u8`, found `u16`
+   |          |
+   |          first introduced with type `u8` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:26:41
@@ -36,7 +52,11 @@ error[E0308]: mismatched types
 LL |     match Some((0u8, Some((1u16, 2u32)))) {
    |           ------------------------------- this expression has type `std::option::Option<(u8, std::option::Option<(u16, u32)>)>`
 LL |         Some((x, Some((y, z)))) | Some((y, Some((x, z) | (z, x)))) => {}
-   |                                         ^ expected `u16`, found `u8`
+   |                        -                ^ expected `u16`, found `u8`
+   |                        |
+   |                        first introduced with type `u16` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:26:50
@@ -44,7 +64,11 @@ error[E0308]: mismatched types
 LL |     match Some((0u8, Some((1u16, 2u32)))) {
    |           ------------------------------- this expression has type `std::option::Option<(u8, std::option::Option<(u16, u32)>)>`
 LL |         Some((x, Some((y, z)))) | Some((y, Some((x, z) | (z, x)))) => {}
-   |                                                  ^ expected `u8`, found `u16`
+   |               -                                  ^ expected `u8`, found `u16`
+   |               |
+   |               first introduced with type `u8` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:26:59
@@ -52,7 +76,11 @@ error[E0308]: mismatched types
 LL |     match Some((0u8, Some((1u16, 2u32)))) {
    |           ------------------------------- this expression has type `std::option::Option<(u8, std::option::Option<(u16, u32)>)>`
 LL |         Some((x, Some((y, z)))) | Some((y, Some((x, z) | (z, x)))) => {}
-   |                                                           ^ expected `u32`, found `u16`
+   |                           -                               ^ expected `u32`, found `u16`
+   |                           |
+   |                           first introduced with type `u32` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:26:62
@@ -60,123 +88,169 @@ error[E0308]: mismatched types
 LL |     match Some((0u8, Some((1u16, 2u32)))) {
    |           ------------------------------- this expression has type `std::option::Option<(u8, std::option::Option<(u16, u32)>)>`
 LL |         Some((x, Some((y, z)))) | Some((y, Some((x, z) | (z, x)))) => {}
-   |                                                              ^ expected `u8`, found `u32`
+   |               - first introduced with type `u8` here         ^ expected `u8`, found `u32`
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:34:42
    |
 LL |     if let Blah::A(_, x, y) | Blah::B(x, y) = Blah::A(1, 1, 2) {
-   |                                          ^    ---------------- this expression has type `main::Blah`
-   |                                          |
-   |                                          expected `usize`, found `isize`
+   |                          -               ^    ---------------- this expression has type `main::Blah`
+   |                          |               |
+   |                          |               expected `usize`, found `isize`
+   |                          first introduced with type `usize` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:38:47
    |
 LL |     if let Some(Blah::A(_, x, y) | Blah::B(x, y)) = Some(Blah::A(1, 1, 2)) {
-   |                                               ^     ---------------------- this expression has type `std::option::Option<main::Blah>`
-   |                                               |
-   |                                               expected `usize`, found `isize`
+   |                               -               ^     ---------------------- this expression has type `std::option::Option<main::Blah>`
+   |                               |               |
+   |                               |               expected `usize`, found `isize`
+   |                               first introduced with type `usize` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:42:22
    |
 LL |     if let (x, y) | (y, x) = (0u8, 1u16) {
-   |                      ^       ----------- this expression has type `(u8, u16)`
-   |                      |
-   |                      expected `u16`, found `u8`
+   |                -     ^       ----------- this expression has type `(u8, u16)`
+   |                |     |
+   |                |     expected `u16`, found `u8`
+   |                first introduced with type `u16` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:42:25
    |
 LL |     if let (x, y) | (y, x) = (0u8, 1u16) {
-   |                         ^    ----------- this expression has type `(u8, u16)`
-   |                         |
-   |                         expected `u8`, found `u16`
+   |             -           ^    ----------- this expression has type `(u8, u16)`
+   |             |           |
+   |             |           expected `u8`, found `u16`
+   |             first introduced with type `u8` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:47:44
    |
 LL |     if let Some((x, Some((y, z)))) | Some((y, Some((x, z) | (z, x))))
-   |                                            ^ expected `u16`, found `u8`
+   |                           -                ^ expected `u16`, found `u8`
+   |                           |
+   |                           first introduced with type `u16` here
 ...
 LL |     = Some((0u8, Some((1u16, 2u32))))
    |       ------------------------------- this expression has type `std::option::Option<(u8, std::option::Option<(u16, u32)>)>`
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:47:53
    |
 LL |     if let Some((x, Some((y, z)))) | Some((y, Some((x, z) | (z, x))))
-   |                                                     ^ expected `u8`, found `u16`
+   |                  -                                  ^ expected `u8`, found `u16`
+   |                  |
+   |                  first introduced with type `u8` here
 ...
 LL |     = Some((0u8, Some((1u16, 2u32))))
    |       ------------------------------- this expression has type `std::option::Option<(u8, std::option::Option<(u16, u32)>)>`
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:47:62
    |
 LL |     if let Some((x, Some((y, z)))) | Some((y, Some((x, z) | (z, x))))
-   |                                                              ^ expected `u32`, found `u16`
+   |                              -                               ^ expected `u32`, found `u16`
+   |                              |
+   |                              first introduced with type `u32` here
 ...
 LL |     = Some((0u8, Some((1u16, 2u32))))
    |       ------------------------------- this expression has type `std::option::Option<(u8, std::option::Option<(u16, u32)>)>`
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:47:65
    |
 LL |     if let Some((x, Some((y, z)))) | Some((y, Some((x, z) | (z, x))))
-   |                                                                 ^ expected `u8`, found `u32`
+   |                  - first introduced with type `u8` here         ^ expected `u8`, found `u32`
 ...
 LL |     = Some((0u8, Some((1u16, 2u32))))
    |       ------------------------------- this expression has type `std::option::Option<(u8, std::option::Option<(u16, u32)>)>`
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:55:39
    |
 LL |     let Blah::A(_, x, y) | Blah::B(x, y) = Blah::A(1, 1, 2);
-   |                                       ^    ---------------- this expression has type `main::Blah`
-   |                                       |
-   |                                       expected `usize`, found `isize`
+   |                       -               ^    ---------------- this expression has type `main::Blah`
+   |                       |               |
+   |                       |               expected `usize`, found `isize`
+   |                       first introduced with type `usize` here
+   |
+   = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:58:19
    |
 LL |     let (x, y) | (y, x) = (0u8, 1u16);
-   |                   ^       ----------- this expression has type `(u8, u16)`
-   |                   |
-   |                   expected `u16`, found `u8`
+   |             -     ^       ----------- this expression has type `(u8, u16)`
+   |             |     |
+   |             |     expected `u16`, found `u8`
+   |             first introduced with type `u16` here
+   |
+   = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:58:22
    |
 LL |     let (x, y) | (y, x) = (0u8, 1u16);
-   |                      ^    ----------- this expression has type `(u8, u16)`
-   |                      |
-   |                      expected `u8`, found `u16`
+   |          -           ^    ----------- this expression has type `(u8, u16)`
+   |          |           |
+   |          |           expected `u8`, found `u16`
+   |          first introduced with type `u8` here
+   |
+   = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:62:42
    |
 LL |     fn f1((Blah::A(_, x, y) | Blah::B(x, y)): Blah) {}
-   |                                          ^    ---- expected due to this
-   |                                          |
-   |                                          expected `usize`, found `isize`
+   |                          -               ^    ---- expected due to this
+   |                          |               |
+   |                          |               expected `usize`, found `isize`
+   |                          first introduced with type `usize` here
+   |
+   = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:65:22
    |
 LL |     fn f2(((x, y) | (y, x)): (u8, u16)) {}
-   |                      ^       --------- expected due to this
-   |                      |
-   |                      expected `u16`, found `u8`
+   |                -     ^       --------- expected due to this
+   |                |     |
+   |                |     expected `u16`, found `u8`
+   |                first introduced with type `u16` here
+   |
+   = note: a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/or-patterns-binding-type-mismatch.rs:65:25
    |
 LL |     fn f2(((x, y) | (y, x)): (u8, u16)) {}
-   |                         ^    --------- expected due to this
-   |                         |
-   |                         expected `u8`, found `u16`
+   |             -           ^    --------- expected due to this
+   |             |           |
+   |             |           expected `u8`, found `u16`
+   |             first introduced with type `u8` here
+   |
+   = note: a binding must have the same type in all alternatives
 
 error: aborting due to 22 previous errors
 
diff --git a/src/test/ui/pattern/pat-tuple-bad-type.stderr b/src/test/ui/pattern/pat-tuple-bad-type.stderr
index 95cca38f7de..598b6a3794e 100644
--- a/src/test/ui/pattern/pat-tuple-bad-type.stderr
+++ b/src/test/ui/pattern/pat-tuple-bad-type.stderr
@@ -12,6 +12,8 @@ LL |         (..) => {}
 error[E0308]: mismatched types
   --> $DIR/pat-tuple-bad-type.rs:10:9
    |
+LL |     match 0u8 {
+   |           --- this expression has type `u8`
 LL |         (..) => {}
    |         ^^^^ expected `u8`, found `()`
 
diff --git a/src/test/ui/pattern/pat-tuple-overfield.stderr b/src/test/ui/pattern/pat-tuple-overfield.stderr
index 25d02b8627c..45b6fd1b4d4 100644
--- a/src/test/ui/pattern/pat-tuple-overfield.stderr
+++ b/src/test/ui/pattern/pat-tuple-overfield.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/pat-tuple-overfield.rs:5:9
    |
+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
    |
@@ -10,6 +12,9 @@ LL |         (1, 2, 3, 4) => {}
 error[E0308]: mismatched types
   --> $DIR/pat-tuple-overfield.rs:6:9
    |
+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/pattern/pattern-ident-path-generics.stderr b/src/test/ui/pattern/pattern-ident-path-generics.stderr
index 338eb6ff0c8..24b5cdf98d5 100644
--- a/src/test/ui/pattern/pattern-ident-path-generics.stderr
+++ b/src/test/ui/pattern/pattern-ident-path-generics.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/pattern-ident-path-generics.rs:3:9
    |
+LL |     match Some("foo") {
+   |           ----------- this expression has type `std::option::Option<&str>`
 LL |         None::<isize> => {}
    |         ^^^^^^^^^^^^^ expected `&str`, found `isize`
    |
diff --git a/src/test/ui/resolve/name-clash-nullary.stderr b/src/test/ui/resolve/name-clash-nullary.stderr
index aeeb0c45191..2de0b6a4969 100644
--- a/src/test/ui/resolve/name-clash-nullary.stderr
+++ b/src/test/ui/resolve/name-clash-nullary.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/name-clash-nullary.rs:2:7
    |
 LL |   let None: isize = 42;
-   |       ^^^^ expected `isize`, found enum `std::option::Option`
+   |       ^^^^  ----- expected due to this
+   |       |
+   |       expected `isize`, found enum `std::option::Option`
    |
    = note: expected type `isize`
               found enum `std::option::Option<_>`
diff --git a/src/test/ui/resolve/resolve-inconsistent-binding-mode.stderr b/src/test/ui/resolve/resolve-inconsistent-binding-mode.stderr
index 61d1001ce91..749ed131b20 100644
--- a/src/test/ui/resolve/resolve-inconsistent-binding-mode.stderr
+++ b/src/test/ui/resolve/resolve-inconsistent-binding-mode.stderr
@@ -26,7 +26,11 @@ error[E0308]: mismatched types
 LL |     match x {
    |           - this expression has type `Opts`
 LL |       Opts::A(ref i) | Opts::B(i) => {}
-   |                                ^ expected `&isize`, found `isize`
+   |               -----            ^ expected `&isize`, found `isize`
+   |               |
+   |               first introduced with type `&isize` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/resolve-inconsistent-binding-mode.rs:16:32
@@ -34,7 +38,11 @@ error[E0308]: mismatched types
 LL |     match x {
    |           - this expression has type `Opts`
 LL |       Opts::A(ref i) | Opts::B(i) => {}
-   |                                ^ expected `&isize`, found `isize`
+   |               -----            ^ expected `&isize`, found `isize`
+   |               |
+   |               first introduced with type `&isize` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error[E0308]: mismatched types
   --> $DIR/resolve-inconsistent-binding-mode.rs:25:36
@@ -42,10 +50,13 @@ error[E0308]: mismatched types
 LL |     match x {
    |           - this expression has type `Opts`
 LL |       Opts::A(ref mut i) | Opts::B(ref i) => {}
-   |                                    ^^^^^ types differ in mutability
+   |               ---------            ^^^^^ types differ in mutability
+   |               |
+   |               first introduced with type `&mut isize` here
    |
    = note: expected type `&mut isize`
               found type `&isize`
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/ui/resolve/resolve-inconsistent-names.stderr b/src/test/ui/resolve/resolve-inconsistent-names.stderr
index 5c87f7c684f..1d3079c90ba 100644
--- a/src/test/ui/resolve/resolve-inconsistent-names.stderr
+++ b/src/test/ui/resolve/resolve-inconsistent-names.stderr
@@ -89,7 +89,11 @@ error[E0308]: mismatched types
 LL |     match x {
    |           - this expression has type `(E, E)`
 LL |         (A, B) | (ref B, c) | (c, A) => ()
-   |                   ^^^^^ expected enum `E`, found `&E`
+   |             -     ^^^^^ expected enum `E`, found `&E`
+   |             |
+   |             first introduced with type `E` here
+   |
+   = note: in the same arm, a binding must have the same type in all alternatives
 
 error: aborting due to 9 previous errors
 
diff --git a/src/test/ui/rfc-2005-default-binding-mode/const.stderr b/src/test/ui/rfc-2005-default-binding-mode/const.stderr
index f25fc300d7f..27efd450b94 100644
--- a/src/test/ui/rfc-2005-default-binding-mode/const.stderr
+++ b/src/test/ui/rfc-2005-default-binding-mode/const.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/const.rs:14:9
    |
+LL |     match &f {
+   |           -- this expression has type `&Foo`
 LL |         FOO => {},
    |         ^^^ expected `&Foo`, found struct `Foo`
 
diff --git a/src/test/ui/rfc-2005-default-binding-mode/lit.stderr b/src/test/ui/rfc-2005-default-binding-mode/lit.stderr
index b0d60c7a4c8..6d18a39606c 100644
--- a/src/test/ui/rfc-2005-default-binding-mode/lit.stderr
+++ b/src/test/ui/rfc-2005-default-binding-mode/lit.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/lit.rs:7:13
    |
+LL |     match &s {
+   |           -- this expression has type `&&str`
 LL |             "abc" => true,
    |             ^^^^^ expected `&str`, found `str`
    |
@@ -10,6 +12,8 @@ LL |             "abc" => true,
 error[E0308]: mismatched types
   --> $DIR/lit.rs:16:9
    |
+LL |     match &s {
+   |           -- this expression has type `&&[u8]`
 LL |         b"abc" => true,
    |         ^^^^^^ expected `&[u8]`, found array `[u8; 3]`
    |
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/suggestions/match-ergonomics.stderr b/src/test/ui/suggestions/match-ergonomics.stderr
index abdb754acc5..559a2d29551 100644
--- a/src/test/ui/suggestions/match-ergonomics.stderr
+++ b/src/test/ui/suggestions/match-ergonomics.stderr
@@ -1,6 +1,8 @@
 error[E0308]: mismatched types
   --> $DIR/match-ergonomics.rs:4:10
    |
+LL |     match &x[..] {
+   |           ------ this expression has type `&[i32]`
 LL |         [&v] => {},
    |          ^^
    |          |
@@ -25,6 +27,8 @@ LL |         [v] => {},
 error[E0308]: mismatched types
   --> $DIR/match-ergonomics.rs:29:9
    |
+LL |     match y {
+   |           - this expression has type `i32`
 LL |         &v => {},
    |         ^^
    |         |
@@ -38,7 +42,7 @@ error[E0308]: mismatched types
   --> $DIR/match-ergonomics.rs:40:13
    |
 LL |     if let [&v] = &x[..] {}
-   |             ^^
+   |             ^^    ------ this expression has type `&[i32]`
    |             |
    |             expected `i32`, found reference
    |             help: you can probably remove the explicit borrow: `v`
diff --git a/src/test/ui/suppressed-error.stderr b/src/test/ui/suppressed-error.stderr
index 846cd2adcd8..c2874ae9a14 100644
--- a/src/test/ui/suppressed-error.stderr
+++ b/src/test/ui/suppressed-error.stderr
@@ -2,7 +2,9 @@ error[E0308]: mismatched types
   --> $DIR/suppressed-error.rs:2:9
    |
 LL |     let (x, y) = ();
-   |         ^^^^^^ expected `()`, found tuple
+   |         ^^^^^^   -- this expression has type `()`
+   |         |
+   |         expected `()`, found tuple
    |
    = note: expected unit type `()`
                   found tuple `(_, _)`