[Issue 23710] New: [REG master] Reachable code inside an 'if (false)' block no longer gets codegen

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23710

          Issue ID: 23710
           Summary: [REG master] Reachable code inside an 'if (false)'
                    block no longer gets codegen
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: regression
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: ibuclaw at gdcproject.org

Consider the following:
---
int test(int i)
{
    int[] foo;
    if (0)
    {
        for (;;)
        {
            import core.stdc.stdio;
            printf("start body\n");
            foo = foo ~ [1,2,3];
L1:
            printf("foo.length = %zu\n", foo.length);
            i += 2;
            if (i > 5)
                return i;
            printf("end body\n");
        }
    }
    goto L1;
}

extern(C) int main() { return test(1); }
---

Actual run-time result:
---
foo.length = 0
end body
foo.length = 0
end body
foo.length = 0
---

Expected run-time result:
---
foo.length = 0
end body
start body
foo.length = 3
end body
start body
foo.length = 6
---

Also noting that when compiling with `-betterC`, there is no error about the
use of RTTI in the array concat expression.

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