On Friday, 11 December 2020 at 11:32:09 UTC, rikki cattermole
wrote:
string is not a built in type. It is an alias defined by
druntime.
https://github.com/dlang/druntime/blob/master/src/object.d#L35
int on the other hand is defined by the compiler. It
understands it.
It doesn't magically understand it. `int` is a keyword and thus
not a legal identifier.
From a grammar perspective, in `(x, y) { }`, x and y are parsed
as types. [1] However, in lambda expressions, when there's a type
only and no parameter (according to the grammar) given, the
compiler treats a single identifier as a parameter with inferred
type. Since `int` is not an identifier, but a keyword, that
treatment does not happen. As you explained correctly, `string`
is merely an identifier and thus seen as a parameter name.
[1] https://dlang.org/spec/grammar.html#Parameters
