Tweak output of type mismatch between "then" and else if arms

[estebank]

error[E0308]: if and else have incompatible types
  --> $DIR/if-else-type-mismatch.rs:5:9
   |
LL |       let _ = if true {
   |  _____________-
LL | |         42i32
   | |         ----- expected because of this
LL | |     } else {
LL | |         42u32
   | |         ^^^^^ expected i32, found u32
LL | |     };
   | |_____- if and else have incompatible types
   |
   = note: expected type `i32`
              found type `u32`

error[E0308]: if and else have incompatible types
  --> file.rs:2:38
   |
LL |     let _ = if false { 3u8; } else { 3u8 };
   |                        ----          ^^^ expected (), found u8
   |                        |  |
   |                        |  help: consider removing this semicolon
   |                        expected because of this
   |
   = note: expected type `()`
              found type `u8`

error[E0308]: if and else have incompatible types
  --> file.rs:3:37
   |
LL |     let _ = if false { 3u8 } else { 3u8; };
   |                        ---          ^^^-
   |                        |            |  |
   |                        |            |  help: consider removing this semicolon
   |                        |            expected u8, found ()
   |                        expected because of this
   |
   = note: expected type `u8`
              found type `()`

error[E0308]: if and else have incompatible types
  --> file.rs:4:37
   |
LL |     let _ = if false { 3i8 } else { 3u8 };
   |                        ---          ^^^ expected i8, found u8
   |                        |
   |                        expected because of this
   |
   = note: expected type `i8`
              found type `u8`

Fix #57348.

[rust-highfive]

r? @nikomatsakis

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[nikomatsakis]

@bors r+

[bors]

📌 Commit 81f2cf0091fc3bc87db2093edc9b5bfca6797008 has been approved by nikomatsakis

[bors]

⌛ Testing commit 81f2cf0091fc3bc87db2093edc9b5bfca6797008 with merge b366f65687a2ede5d206408861828dc32afbd17c...

[bors]

💔 Test failed - status-appveyor

[pietroalbini]

@bors retry
AppVeyor... what's wrong with you today?

[estebank]

rebased to get bors unstuck

@bors r=nikomatsakis

[bors]

📌 Commit 54fe1c023a178d6f27c88de90cfdeda926584d19 has been approved by nikomatsakis

[bors]

☔ The latest upstream changes (presumably #57580) made this pull request unmergeable. Please resolve the merge conflicts.

[estebank]

Fixed merge conflict

@bors r=nikomatsakis

[bors]

📌 Commit 9567544 has been approved by nikomatsakis

[bors]

⌛ Testing commit 9567544 with merge 0bc0015...

[bors]

☀️ Test successful - checks-travis, status-appveyor
Approved by: nikomatsakis
Pushing 0bc0015 to master...