disallow potentially non-const initializers of const constructors

[sigmundch]

According to the spec, the following code should give an error, because the initializer is not a potentially const expression:

class A {
  final x;
  const A() : x = 1.toString();
}

main() => const A();

I'll shortly submit this as a test under language/src (CL in progress). Other (more realistic) examples to consider:
 const A(p) : x = p.toString();
 const A() : x = new List();

[DartBot]

This comment was originally written by zundel@google.com

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Set owner to zundel@google.com.

[DartBot]

This comment was originally written by zundel@google.com

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oops, saw this was tagged by the VM (also an issue for dartc

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Removed the owner.

[DartBot]

This comment was originally written by ief...@unipro.ru

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There are co19 tests for this:

LangSpecTest/07_Classes/5_Constructors/3/Constant/Constructors/A04/t02
LangSpecTest/07_Classes/5_Constructors/3/Constant/Constructors/A04/t03
LangSpecTest/07_Classes/5_Constructors/3/Constant/Constructors/A05/t01
LangSpecTest/07_Classes/5_Constructors/3/Constant/Constructors/A05/t02

[iposva-google]

There were many changes in the const/final and initialization area. Not sure if this is still a valid bug report.

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Set owner to @mhausner.
Added Accepted label.

[DartBot]

This comment was originally written by @mhausner

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I will fix the compiler to require compile time constants for all default initializer expressions in const constructors.

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Added this to the M1 milestone.

[DartBot]

This comment was originally written by @mhausner

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This is the same issue as issue #392. It is not enough to require that the initializers are constant expressions. The must be "potentially constant expressions" as elaborated in the language spec. Implementing this is non-trivial.

[iposva-google]

Removed this from the M1 milestone.
Added this to the M2 milestone.

[iposva-google]

Removed this from the M2 milestone.
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[iposva-google]

Removed this from the M3 milestone.
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[larsbak]

Removed this from the M4 milestone.
Added this to the M5 milestone.

[iposva-google]

Removed Priority-Medium label.
Added Priority-Unassigned label.

[iposva-google]

Srdjan had some fixes in that general area as well. If I remember correctly they might solve the "potentially constant expression" problem.

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cc @sgmitrovic.
Removed this from the M5 milestone.
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Added Priority-Medium label.

[ghost]

Set owner to @sgmitrovic.
Added Started label.

[ghost]

Missing piece: check initializers for legal operations.

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Set owner to @mhausner.
Added Accepted label.

[iposva-google]

Added Duplicate label.
Marked as being merged into #392.