gcc/testsuite/gdc.test/fail_compilation/fail19038.d

   1 /* TEST_OUTPUT:
   2 ---
   3 fail_compilation/fail19038.d(21): Error: cannot implicitly convert expression `a` of type `string[][]` to `const(string)[][]`
   4 fail_compilation/fail19038.d(23): Error: cannot modify `const` expression `c[0]`
   5 ---
   6  * Credit: yshui
   7  * https://github.com/dlang/dmd/pull/8413#issuecomment-401104961
   8  * https://issues.dlang.org/show_bug.cgi?id=19038
   9  */
  10
  11
  12 void test()
  13 {
  14     /* string[][] is not implicitly converible to const(string)[][],
  15      * and there is good reason why:
  16      *
  17      * https://stackoverflow.com/questions/5055655/double-pointer-const-correctness-warnings-in-c
  18      */
  19
  20     string[][] a = [["Lord"]];
  21     const(string)[][] b = a; // assume this works (and it should not)
  22     const(string)[] c = ["Sauron"];
  23     c[0] = "Mordor"; // invalid, because c[0] is const(string)
  24
  25     b[0] = c; // valid, b[0] is const(string)[]
  26     // But now, a[0] has become c
  27     a[0][0] = "Nazgul"; // valid, because a[0][0] is string
  28     // But this also changes c[0], which shouldn't be possible
  29 }