Type Annotation Syntax On The Right. Use of def, var and val in lieu of var, T x, final x.

[DartBot]

This issue was originally filed by Ray.Rac...@gmail.com

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What steps will reproduce the problem?
1.Write Dart code as proposed.
2.
3.

What is the expected output? What do you see instead?
Optional type annotation to be on the right of the identifier. Use of val to replace final and def to denote the start of a method/function definition.

What version of the product are you using? On what operating system?
All

Please provide any additional information below.

1. Use of the type annotation on the right allows for better readability and more importantly positions Dart to more easily handle future syntax extension and language evolution. Dart language designers know the pros / cons here already.

val x Int = 3
var y String = 'Gilad'
def rev (s String)String => s.reverse ()

2. Use of val of final is more intuitive, pithy aligns code nicely with var and def.

3. Placing the type on the right supports (requires) the use of a keyword to denote a method / function definition. Use of 'def' is suggested.

Primary Reason Not to Change.

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The stated reason to keeping type annotations on the left is familiarity for the mainstream programmer as (I assume) many of the new Dart new comers will be from C#, Java.

1. There are as many non-Java people coming to Dart who will not have any basis. Those from JS, Ruby, Python will be familiar with 'def' for example.

2. Universally Java/C# people coming to Scala have been positive with this syntax as cleaner and enhancing readability. (Scala adoption issues center on the complex type system and not its base declaration syntax).

3. It is apparent that Dart has been painted, unfairly, as "its just Java". These small syntax changes,off a sense of "freshness" to the Dart language that will soon be appreciated by new comers.

Adaption has shown the barrier to new syntax is very low barrier and immediately appreciated by the majority of Java users for its basic elegance and cleaness.

People will be much more receptive to Dart from such a sense "newness" and "freshness" about it from such minor syntax cleanups yet retains all the core familiar concepts.

[DartBot]

This comment was originally written by drfibonacci@google.com

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

[DartBot]

This comment was originally written by carstenkl...@yahoo.de

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Personally I do not support the suggestion to replace 'final' by 'val'. If it were to be replaced, then by 'const'. And proper alignment in the editor is not such a big deal at all, see proposal below.

Additionally, I believe that one should remove the 'var' keyword from the language because it is redundant.

As for type hints, one could use the proposal made below.

Proposal:

Declaring an initialized variable:

x = 5;

Declaring a typed, initialized variable:

x : num = null;

or

x : int = 5;

Declaring a final untyped variable:

x : final = 5;

Declaring a final, typed variable:

x : final int = 5;

Declaring uninitialized variables is supported by the language, and variables with a type hint of <dynamic> should be initialized with null.
Variables with type hints that are of type <num> should be initialized with 0.
Strings and other typed variables must be initialized with null.

Declaring an untyped variable and omitting the initializer:

x;

Declaring a typed variable and omitting the initializer:

x : int;

and so on. I think you get the picture.

[DartBot]

This comment was originally written by jat@google.com

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If you don't have some difference between declaring a variable and an expression, how do you distinguish likely typos? In many dynamic languages, this is a common problem where you thought you were assigning to an existing variable but typo'd it and instead created a new one.

Regarding type on the left or type on the right, I am not sure why it is claimed that on the right is more readable. I would bet if you take the total number of programmer hours spent in particular languages, those using declarations on the left would outweigh those on the right. I agree that having a : type after a variable declaration does fit optional types better, but I think you will then need a keyword to introduce declarations like in Scala. Then if you usually use types, you will be typing more rather than less: "var foo: int;" rather than "int foo;".

[munificent]

jat@, I believe the implication with the suggestion here is that "var" would be the keyword to indicate a variable declaration. I don't think we're talking implicit declaration here. So:

var foo = 123; // both current and proposed style
int foo = 123; // current
var foo : int = 123; // proposed

[DartBot]

This comment was originally written by jat@google.com

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That wasn't my interpretation of comment #­2 - it looked like he was suggesting dropping the keyword to declare a variable.

[munificent]

Oh, sorry, my mistake. Note to self: read all comments on bug before opening my mouth.

[gbracha]

Hi,

My syntactic preferences are well known, and I have great sympathy for what you are saying. However:
a. We are trying to be very conservative.
b. Syntax is a barrier to adoption.
c. I am well aware of the implications for future evolution of using the brittle C style conventions.
d. Small adjustments may be made, but don't count on it.
e. Not everyone on the team agrees on these issues, so they are not easy to change. Language design on a large industrial language requires the ability to compromise and look at the big picture.

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Set owner to @gbracha.

[DartBot]

This comment was originally written by Ray.Rac...@gmail.com

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Of course I was looking at the big picture. If all unfolds as it well mayhappen Dart is destined to be the most widely used language in the world with a life span of many decades if not well over a century. Ergo what the heck was worth a shot!

Please close, along with companion issue #99.

[gbracha]

Closing at submitter's request. If only all feature requesters were so accommodating ...

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Added WontFix label.