Fix if_same_then_else false positive

[jorpic]

This fixes false positive in #3559.
The problem was that SpanlessEq does not check patterns in declarations. So this two blocks considered equal.

if true {
    let (x, y) = foo();
} else {
   let (y, x) = foo();
}

Not sure if the proposed change is safe as SpanlessEq is used extensively in other lints, but I tried hard to come up with counterexample and failed.

[jorpic]

Don't understand how my change causes build failure.
Seems that hir::ExprKind::Err was introduced in rust-lang/rust@a5c52c7 11 days ago.

Should I address these errors in this PR?

error[E0004]: non-exhaustive patterns: `Err` not covered
   --> clippy_lints\src\utils\inspector.rs:172:11
    |
172 |     match expr.node {
    |           ^^^^^^^^^ pattern `Err` not covered
error[E0004]: non-exhaustive patterns: `Err` not covered
   --> clippy_lints\src\loops.rs:691:11
    |
691 |     match expr.node {
    |           ^^^^^^^^^ pattern `Err` not covered
error[E0004]: non-exhaustive patterns: `Err` not covered
   --> clippy_lints\src\utils\author.rs:205:15
    |
205 |         match expr.node {
    |               ^^^^^^^^^ pattern `Err` not covered
error[E0004]: non-exhaustive patterns: `Err` not covered
   --> clippy_lints\src\utils\hir_utils.rs:410:15
    |
410 |         match e.node {
    |               ^^^^^^ pattern `Err` not covered
error[E0004]: non-exhaustive patterns: `Err` not covered
  --> clippy_lints\src\utils\sugg.rs:58:19
   |
58 |             match expr.node {
   |                   ^^^^^^^^^ pattern `Err` not covered
error[E0004]: non-exhaustive patterns: `Err` not covered
   --> clippy_lints\src\utils\sugg.rs:128:15
    |
128 |         match expr.node {
    |               ^^^^^^^^^ pattern `Err` not covered
error: aborting due to 6 previous errors

[oli-obk]

You probably just have an outdated master branch. If you rebase over the master branch of this repository, everything should work again

[mati865]

It's upstream breakage, rust-lang/rust#56999 was merged last night.
You can wait until somebody fixes it or do it yourself (preferrably in the other PR).

[flip1995]

Fixed in #3591

[bors]

☔ The latest upstream changes (presumably #3587) made this pull request unmergeable. Please resolve the merge conflicts.

[matthiaskrgr]

nit: I'd like this line to be slightly more descriptive, something like
// false positive if_same_then_else, let(x,y) vs let(y,x), see #3559

[jorpic]

Fixed that. Thanks for feedback!

[phansch]

@bors r+ thanks!

[bors]

📌 Commit 911a752 has been approved by phansch

[bors]

⌛ Testing commit 911a752 with merge 6f39128...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: phansch
Pushing 6f39128 to master...