support direct invocations on grouped expressions

[jvasileff]

Direct invocations on grouped expressions do not currently work:

shared void run() {
    value a = ("hello ".plus) { "world"; };   
    value b = (("hello ".plus)) { "world"; }; 
    value c = 1.plus { 2; };        
    value d = (1.plus) { 2; };      
    value e = ((1.plus)) { 2; };    
    //value f = (Singleton)(10);

    print ({a,b,c,d,e});
}

prints:

{ ceylon.language::JsCallable@1, ceylon.language::JsCallable@2, 3, ceylon.language::JsCallable@3, ceylon.language::JsCallable@4 }

Uncommenting the value f line results in:

/Users/jvasileff/Dropbox/Repos/ceylon/ceylon-dist/dist/repo/ceylon/language/1.2.0/ceylon.language-1.2.0.js:5189
$1an_=$1an;$_Object(singleton$);Sequence({Element$Sequence:$$targs$$.Element$S
                                                                    ^
TypeError: Cannot read property 'Element$Singleton' of undefined
    at Object.Singleton (/Users/jvasileff/Dropbox/Repos/ceylon/ceylon-dist/dist/repo/ceylon/language/1.2.0/ceylon.language-1.2.0.js:5189:80)
    at run (/Users/jvasileff/Dropbox/Repos/jv/simple/modules/simple/1.0.0/simple-1.0.0.js:36:12)

See also ceylon/ceylon-spec#1449

[chochos]

But this is a new feature, right?

[gavinking]

It's not new, but I now think the typechecker should actually disallow all these things.

[gavinking]

Moved.