Makes finalVarOrType mandatory for the typedef

[DartBot]

This issue was originally filed by boost...@gmail.com

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typedef use formalParameterList for declare an alias of function type.
But this rule surprise many users.
For example.

int f( int x ) => x ;
typedef int type( int ) ;

void main()
{
    type t = f ;
    t("a") ; // no static type warning is issued.
}

This is because int is treated as an identifier in simpleFormalParameter.
So int is just a name of parameter and its type is Dynamic.

But most user who don't read spec expect above typedef to annotate that the static type of parameter is int.
That's why they surprise the above code doesn't issue a static type warning.

To solve this issue, I propose to make finalVarOrType in mandatory for the typedef.
Under the proposed change, above typedef must be rewritten as
typedef int f( var int ) ;

This makes it apparent for all users that int is just a name of parameter and its type is Dynamic since it use var.

[floitschG]

Removed Type-Defect label.
Added Type-Enhancement, Area-Language, Triaged labels.

[gbracha]

typedefs need to be extended to cover type aliases in general. I'd like to see a different syntax of function type aliases. We'll see what can be done.

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Set owner to @gbracha.
Added Accepted label.

[anders-sandholm]

Added apr30-triage label.

[anders-sandholm]

Removed apr30-triage label.

[anders-sandholm]

Added triage1 label.

[anders-sandholm]

Added this to the M1 milestone.
Removed triage1 label.

[gbracha]

We've decided that, post M1, we will generalize typedef to allow aliasing for arbitrary types. Details TBD. Reclassifying this accordingly.

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Removed this from the M1 milestone.
Added this to the Later milestone.

[lrhn]

We now have mixin-application typedefs.
Still no type aliases, though (e.g. "typedef IntList = List<int>"), which would be great!

[kasperl]

Removed this from the Later milestone.
Added Oldschool-Milestone-Later label.

[kasperl]

Removed Oldschool-Milestone-Later label.

[lrhn]

Closed incorrect issue, this one is still open.

[matanlurey]

This is stale now that we have the new function syntax.