Types of lambda args

[Paul Backus]

On Wednesday, 26 August 2020 at 15:57:37 UTC, Cecil Ward wrote:
>
> Ah! That’s the vital missing piece - I didn’t realise it was 
> like a template - I just thought it was an ordinary plain 
> anonymous function, not a generic. All makes sense now.

Fun fact: you can see the "de-sugared" version of many language 
constructs like this by looking at the compiler's AST output. For 
example, given a source file `lambda.d` with the following 
contents:

     alias fun = (x) => x*x;

The command `dmd -vcg-ast lambda.d` produces as output the file 
`lambda.d.cg`, with the following contents:

     import object;
     alias fun = __lambda3(__T1)(x)
     {
     	return x * x;
     }
     ;

The syntax is a little different from normal D code, but you can 
see the template argument `__T1` appear in addition to the 
function argument `x`.