f90_correct: fix rank mismatch in dt17.f90

[bryanpkc]

Line 45 in test/f90_correct/src/dt17.f90 contains a rank mismatch which causes Flang to emit a warning:

F90-W-0155-The number of subscripts is less than the rank of ia (test/f90_correct/src/dt17.f90: 45)
  0 inform,   1 warnings,   0 severes, 0 fatal for check2

Its sibling test, dt17b.f90, uses the correct rank for ia on the same line. Presumably this is just a typo in the first test case; this PR fixes the typo.

Incidentally, gfortran gives an error on this test case:

dt17.f90:45:81:

   45 |       write(*,'(a,a,i1,a,i1,a,i4,a,i4)') s,'a(',i,',',j,')%i=',a(i,j)%i,' != ',ia(i)
      |                                                                                 1
Error: Rank mismatch in array reference at (1) (1/2)

Is there any reason why Flang only gives a warning and not a severe error?

[gklimowicz]

Looking back at the history of this change in the original PGI compiler, it looks like this was an intentional extension. When you compile with -Mstandard, it flags this as an error.

[bryanpkc]

I tried adding -Mstandard already; Flang still just prints a warning and not a severe error.

[gklimowicz]

Oh, sorry, yes. The only real difference is that with -Mstandard, the warning comes with a different warning number and the message that this use is an extension.

I think in general, even under -Mstandard, flang treats non-standard Fortran or use of extensions as warning and not as severe errors. That was probably considered a feature at the time the code was written.

@mleair may be able to provide some additional insights into the underlying philosophy here.

[bryanpkc]

In ref_array (tools/flang1/flang1exe/semutil.c), I think I understand the code that handles "overindexed subscript reference" (the Cray Fortran documentation states that nooverindex is the default). But I don't understand the part that handles "a member reference of a subscripted derived type"; I wasn't able to construct a rank mismatch example where SST_IDG(stktop) == S_DERIVED. Could you give me some pointer?