https://issues.dlang.org/show_bug.cgi?id=14061

          Issue ID: 14061
           Summary: Refused array concat at compile-time
           Product: D
           Version: D2
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: regression
          Priority: P1
         Component: DMD
          Assignee: nobody@puremagic.com
          Reporter: bearophile_hugs@eml.cc

int foo(int[] a) {
    foreach (immutable x; a)
        auto b = a ~ x;
    return 0;
}
void main() {
    enum r = foo([1]);
}


dmd 2.067alpha gives:

test.d(3): Error: a ~ x cannot be interpreted at compile time
test.d(7):        called from here: foo([1])

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