VM treats an additive expression with strings literals as a constant expression

[DartBot]

This issue was originally filed by ms...@unipro.ru

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What steps will reproduce the problem?
Run the following test:
class C {
  static final String s = "One" + "Two";
}

main() {
  print(C.s);
}

What is the expected output? What do you see instead?
Expected: compile-time error.
Actual: "OneTwo"

What version of the product are you using? On what operating system?
Dart VM r2810, Ubuntu 10.04

Please provide any additional information below.
According to the section 10.1 of the Language Specification, "An expression of one of the forms e1+e2, e1 - e2, e1 * e2, e1 / e2, e1 > e2, e1 < e2, e1 >= e2, e1 <= e2 or e1 % e2, where e1 and e2 are constant expressions that evaluate to a numeric value."
can be a constant expression, but an additive expression with string literals can't.

[dgrove]

Added Area-VM, Triaged labels.

[DartBot]

This comment was originally written by @mhausner

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An earlier version of the language spec specified "a" + "b" to be a compile time constant. I don't see this in the current version of the spec. Will check with Gilad.

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Set owner to @mhausner.

[DartBot]

This comment was originally written by @mhausner

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Spoke with Gilad. This is an omission in the language spec. He'll fix the spec, to allow concatenation of two compile time constant string literals with + to be a compile time constant.

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Added WontFix label.