[flang-commits] [flang] [flang][Semantics] Check defined-operator purity at the use site (PR #229976)

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+! RUN: %python %S/test_errors.py %s %flang_fc1
+! F2018 C1595: a procedure referenced from a pure subprogram must be pure,
+! including references through defined operators. The operator's generic
+! is declared in the module; the check must use the use site.
+
+module pure_op_mod
+  implicit none
+  type, public :: pv_type
+    real :: x = 0.0, y = 0.0
+  end type pv_type
+
+  interface operator(+)
+    module function pv_add(a, b) result(r)
+      type(pv_type), intent(in) :: a, b
+      type(pv_type) :: r
+    end function pv_add
+  end interface operator(+)
+
+  interface operator(*)
+    module function pv_scale(s, v) result(r)
+      real, intent(in) :: s
+      type(pv_type), intent(in) :: v
+      type(pv_type) :: r
+    end function pv_scale
+  end interface operator(*)
+
+  interface operator(-)
+    pure module function pv_sub(a, b) result(r)
+      type(pv_type), intent(in) :: a, b
+      type(pv_type) :: r
+    end function pv_sub
+  end interface operator(-)
+end module pure_op_mod
+
+submodule (pure_op_mod) pure_op_smod
+  implicit none
+contains
+  module procedure pv_add
+    r%x = a%x + b%x
+    r%y = a%y + b%y
+  end procedure pv_add
+
+  module procedure pv_scale
+    r%x = s * v%x
+    r%y = s * v%y
+  end procedure pv_scale
+
+  module procedure pv_sub
+    r%x = a%x - b%x
+    r%y = a%y - b%y
+  end procedure pv_sub
+end submodule pure_op_smod
+
+program main
+  use pure_op_mod
+  implicit none
+  type(pv_type) :: a, b, m
+  a = pv_type(1.0, 2.0)
+  b = pv_type(3.0, 4.0)
+  ! Impure defined operators are fine outside a pure subprogram.
+  m = 0.5 * (a + b)
+  m = a - b
+  m = midpoint(a, b)
+contains
+  pure function midpoint(p, q) result(r)
+    type(pv_type), intent(in) :: p, q
+    type(pv_type) :: r
+    ! A pure defined operator may be referenced.
+    r = p - q
+    !ERROR: Procedure 'pv_add' referenced in pure subprogram 'midpoint' must be pure too
+    !ERROR: Procedure 'pv_scale' referenced in pure subprogram 'midpoint' must be pure too
+    r = 0.5 * (p + q)
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shivaramaarao wrote:

added new tests into pure01.f90

https://github.com/llvm/llvm-project/pull/229976