Fix measurement code causes E1017 and type mismatch

[rhysd]

Hi,

thank you for exciting new-year present! I tried the measurement code in README.md on my local and noticed it caused an error as follows:

E1017: Variable already declared: sum

Though I'm not fully understanding the grammar, it seems that let is used for declaration in new syntax. is_decl is set to true on :let or :const so I guess assignment to existing variable should be in var = expr style.

vim9/src/vim9compile.c

Line 2747 in f9a84f6

if (is_decl)

After this fix above E1017 no longer occurred.

[rhysd]

I also found that the measurement code still caused a type error because return type was not set to VimNew.

It seems that function return type is void by default here if type annotation is missing:

vim9/src/userfunc.c

Line 2862 in f9a84f6

fp->uf_ret_type = &t_void;

And VimNew returns number so its return type must be typed. After this fix, I confirmed the measurement code runs correctly. And vim9 is far faster! 👍

4499998500000
Vim old:   6.321314
4499998500000
Vim new:   0.138511