Object equality comparison for disjunctive patterns

[CypherPotato]

As discussed in #8028 (reply in thread), we can check if a value is part of the set with the is operator:

int value = 20;
if (value is 20 or 30 or 40) {
    // something
}

but this expression does not work for non-constant values. The proposal is to check whether the value is still part of a set, through its Equals method or == operator, for each embedded value, such as:

int value = 20;
if (value == 20 or 30 or 40) {
    // something
}

// should work for any expression
if (value == other1 or other2 or other3) {
    // something
}

Which would be lowered to:

if (value == other1 || value == other2 || value == other3) {
    // something
}

or even

if (value.Equals(other1) || value.Equals(other2) || value.Equals(other3)) {
    // something
}

Something like this would be more syntax sugar, but it would reduce the amount of code needed to achieve the given goal.

[HaloFour]

I don't believe the or syntax could be used here as that is specific to disjunctive patterns, and that had to be different from || already to disambiguate it from Boolean expressions. Patterns are designed to apply only to constant values and there has been no discussion to allow patterns to support variables in general.

[CypherPotato]

The mention of disjunctive patterns is to express the idea of checking whether X == Y || Z, without having to rewrite X everytime, as X == Y || X == Z. Also I would like you to link to the discussion that concluded that it would not be a good idea to check variables/references in this way, to help me understand it.

[HaloFour]

Here's a comment within a discussion: #2850 (comment)

It doesn't rule out revisiting this in the future, just that it wasn't part of the design.

[huoyaoyuan]

It's basically distributive property on binaryOp over patternOp:

value0 binaryOp (value1 patternOp value2 patternOp ...)
becomes
(value0 binaryOp value1) patternOp (value0 binaryOp value2) patternOp ...