Print error rather than add symbol

Author: Leporacanthicus

flang/lib/Semantics/resolve-names.cpp

@@ -1487,8 +1487,9 @@ class OmpVisitor : public virtual DeclarationVisitor {
     auto &name = std::get<parser::Name>(procDes.u);
     auto *symbol{FindSymbol(NonDerivedTypeScope(), name)};
     if (!symbol) {
-      symbol = &MakeSymbol(context().globalScope(), name.source, Attrs{});
-      Resolve(name, *symbol);
+      context().Say(name.source,
+          "Implicit subroutine declaration '%s' in !$OMP DECLARE REDUCTION"_err_en_US,
+          name.source);
     }
     return true;
   }

flang/test/Semantics/OpenMP/declare-reduction-error.f90

@@ -0,0 +1,11 @@
+! RUN: not %flang_fc1 -emit-obj -fopenmp -fopenmp-version=50 %s 2>&1 | FileCheck %s
+
+subroutine initme(x,n)
+  integer x,n
+  x=n
+end subroutine initme
+
+subroutine subr
+  !$omp declare reduction(red_add:integer(4):omp_out=omp_out+omp_in) initializer(initme(omp_priv,0))
+  !CHECK: error: Implicit subroutine declaration 'initme' in !$OMP DECLARE REDUCTION
+end subroutine subr