Multiple if-let arms can be replaced with match

[In-line]

Example

if let TestEnum::B(_) = *self {
    return true;
}
if let TestEnum::C(_) = *self {
    return true;
}
false

Could be written as:

match self {
    TestEnum::B(_) | TestEnum::C(_) => true,
    _ => false,
}

Playground link

[In-line]

Or matches!(self, TestEnum::B(_) | TestEnum::C(_))

[camsteffen]

Should also include

if let Pat = x { .. } else if let PatB = x { .. }

and (any combination of if let and match)

if let PatB = x { .. }
match x { .. }

and any nested combination

if let PatB = x {
    match x { .. }
}

Should not include

if let Pat = x {
    *x = ..;
}
if let PatB = x {}

I would call this redundant_match. Unfortunately we already have redundant_pattern_matching so I would rename that to needless_match.

[camsteffen]

@rustbot claim

I think I will just enhance collapsible_match. Another idea is mergeable_match since this may be slightly less controversial than collapsible_match. The difference is that collapsible_match (currently) composes patterns into a single pattern.

[tamaroning]

@camsteffen Hi, are you going to fix this issue? If not, I am thinking of doing it.

[camsteffen]

@tamaroning Sure you can take it.

[tamaroning]

I confirmed that collapsible_match already covers the following case (mentioned above).

if let PatB = x {
    match x { .. }
}