Locals are a leaky abstraction. The leaks should be fixed as much as possible.

Open problems

Locals also don't work with undo. On the left hand side, they should bind locals.

There is still an issue with locals and fry:

[ 10 ] [
    0 '[ [let | A [ 10 ] | A _ + ] ] call .
] unit-test

Locals expands macros at parse time which is a problem in this case:

USING: math sequences locals combinators.short-circuit.smart ;
IN: foo

GENERIC: foo ( a -- b )

M: string foo reverse ;
M: integer foo neg ;

:: bar ( a -- b )
   { [ a foo ] } && ;

Fixed

Locals and macros which treat quotations as sequences

:: (funny-macro-test) ( obj quot -- ? ) { quot } 1&& ; inline
: funny-macro-test ( n -- ? ) [ odd? ] (funny-macro-test) ;

\ funny-macro-test must-infer
[ t ] [ 3 funny-macro-test ] unit-test
[ f ] [ 2 funny-macro-test ] unit-test

! Fry and locals

[ 10 ] [
    [let | |
        0 '[ [let | A [ 10 ] | A _ + ] ] call .
    ]
] unit-test

! Smart combinators and wlet

:: wlet-&&-test ( a -- ? )
    [wlet | is-integer? [ a integer? ]
            is-even? [ a even? ]
            >10? [ a 10 > ] |
        { [ is-integer? ] [ is-even? ] [ >10? ] } &&
    ] ;

[ f ] [ 1.5 wlet-&&-test ] unit-test
[ f ] [ 3 wlet-&&-test ] unit-test
[ f ] [ 8 wlet-&&-test ] unit-test
[ t ] [ 12 wlet-&&-test ] unit-test