Error in Dart spec 6.1 Function Declarations

[DartBot]

This issue was originally filed by [email protected]

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The Draft Version 0.05, 6.1 Function Declarations reads:

A function declaration of the form
 T0 id(T1 a1 , . . . , Tn an , [Tn+1 xn+1 = d1 , . . . , Tn+k xn+k = dk ){s}
 is equivalent to a variable declaration of the form
 final F id = (T1 a1 , . . . , Tn an , [Tn+1 xn+1 = d1 , . . . , Tn+k xn+k = dk ]){s},
where F is the function type alias (13.3.1)
 typedef T0 F (T1 a1 , . . . , Tn an , [Tn+1 xn+1 , . . . , Tn+k xn+k ]).

Actually, this forms are not equivalent: first form can be placed anywhere, but second only as a local variable. Placing the second form at isolate or class level causes compile error: "initializer must be a compile time constant".

This is because a function literal is not a compile time constant (10.1 Constants). This is not in line with the fact that a "constant constructor invocation" is a compile time constant, so if a programmer really needs a function to be a compile-time constant, he/she can implement it as a method wrapped in a class constant. So the proposal is to list function literal as a compile time constant, and leave 6.1 Function Declarations intact.

[DartBot]

This comment was originally written by [email protected]

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Added Area-Language, Triaged labels.

[gbracha]

We are leaning toward making function literals compile-time constants, at least for top level ones. So that may indeed resolve the issue.

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Set owner to @gbracha.
Added Accepted label.

[DartBot]

This comment was originally written by [email protected]

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Please note that there is a typo in the spec:

A function declaration of the form
T0 id(T1 a1 , . . . , Tn an , [Tn+1 xn+1 = d1 , . . . , Tn+k xn+k = dk ){s}
                                                                       ^
                                                                       |
                                                                    missing ]

[gbracha]

Resolved the typo in 0.08 draft.

[anders-sandholm]

Added this to the M1 milestone.

[gbracha]

FWIW, final top level/static variables no longer need to be constant so that issue is not a concern. We are reviewing a series of bugs and issues relating to function declarations and will resolve this bug in that context.

[gbracha]

Added Done label.