[PATCH] D85363: [flang] Add options to control IMPLICIT NONE

[Tim Keith via Phabricator via llvm-commits]

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Add `-fimplicit-none-type-always` to treat each specification-part
like it has `IMPLICIT NONE`. This is helpful for enforcing good Fortran
programming practices. We might consider something similar for
`IMPLICIT NONE(EXTERNAL)` as well.

Add `-fimplicit-none-type-never` to ignore occurrences of `IMPLICIT NONE`
and `IMPLICIT NONE(TYPE)`. This is to handle cases like the one below,
which violates the standard but it accepted by some compilers:

  subroutine s(a, n)
    implicit none
    real :: a(n)
    integer :: n
  end


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D85363

Files:
  flang/documentation/Extensions.md
  flang/include/flang/Common/Fortran-features.h
  flang/lib/Semantics/resolve-names.cpp
  flang/test/Semantics/implicit09.f90
  flang/test/Semantics/implicit10.f90
  flang/tools/f18/f18.cpp

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