where {T} vs where T

[odow]

Following https://github.com/jrevels/YASGuide#other-syntax-guidelines, I propose that all occurrences of where T are replaced with where {T}.

This makes things clearer, and unifies the syntax with more complicated where statements (e.g., with multiple terms) which require {}.

Bad:

function foo(x::T) where T <: Integer
    return 2x
end

Good:

function foo(x::T) where {T <: Integer}
    return 2x
end

p.s. very cool. Thanks for working on this.

Edit: to make the point more explicit:

Also Bad:

function foo(x::T) where T
    return 2x
end

bar(x::T) where T = 2x

Good:

function foo(x::T) where {T}
    return 2x
end

bar(x::T) where {T} = 2x

[StefanKarpinski]

What about where T but where {T <: Integer}. There is a slight wrinkle that people prefer the { } version in the one-line case:

foo(x::T) where T = 2x # confusing
foo(x::T) where {T} = 2x # clearer

So a possible rule would be this:

• no braces in long form function definition when the where clause is just a single typevar
• otherwise always enclose in braces

[odow]

The fewer special exceptions the better.

For the sake of two characters, instead of having to remember (and code, maintain, etc) if long form and single type var, it's just "Always enclose in braces."

[StefanKarpinski]

Surveying Base Julia, the vast majority of even multiline function definitions with just a single name after the where use curly braces, so it seems like people are fine to just use them consistently.

[domluna]

Added this in 8944eaa