Workaround for fparser behaviour

loki/frontend/fparser.py

@@ -2100,8 +2100,17 @@ def visit_If_Construct(self, o, **kwargs):
             else_if_stmt_index, else_if_stmts = zip(*else_if_stmts)
         else:
             else_if_stmt_index = ()
-        else_stmt = get_child(o, Fortran2003.Else_Stmt)
-        else_stmt_index = o.children.index(else_stmt) if else_stmt else end_if_stmt_index
+
+        # Note: we need to use here the same method as for else-if because finding Else_Stmt
+        # directly and checking its position via o.children.index may give the wrong result.
+        # This is because Else_Stmt may erronously compare equal to other node types.
+        # See https://github.com/stfc/fparser/issues/400
+        else_stmt = tuple((i, c) for i, c in enumerate(o.children) if isinstance(c, Fortran2003.Else_Stmt))
+        if else_stmt:
+            assert len(else_stmt) == 1
+            else_stmt_index, else_stmt = else_stmt[0]
+        else:
+            else_stmt_index = end_if_stmt_index
         conditions = as_tuple(self.visit(c, **kwargs) for c in (if_then_stmt,) + else_if_stmts)
         bodies = tuple(
             tuple(flatten(as_tuple(self.visit(c, **kwargs) for c in o.children[start+1:stop])))

tests/test_control_flow.py

@@ -10,7 +10,7 @@
 import numpy as np
 
 from conftest import jit_compile, clean_test, available_frontends
-from loki import OMNI, Subroutine, FindNodes, Loop, Conditional, Node
+from loki import OMNI, Subroutine, FindNodes, Loop, Conditional, Node, Intrinsic
 
 
 @pytest.fixture(scope='module', name='here')
@@ -455,3 +455,45 @@ def test_conditional_bodies(frontend):
         c.else_body and isinstance(c.else_body, tuple) and all(isinstance(n, Node) for n in c.else_body)
         for c in conditionals
     )
+
+
+@pytest.mark.parametrize('frontend', available_frontends())
+def test_conditional_else_body_return(frontend):
+    fcode = """
+FUNCTION FUNC(PX,KN)
+IMPLICIT NONE
+INTEGER,INTENT(INOUT) :: KN
+REAL,INTENT(IN) :: PX
+REAL :: FUNC
+INTEGER :: J
+REAL :: Z0, Z1, Z2
+Z0= 1.0
+Z1= PX
+IF (KN == 0) THEN
+  FUNC= Z0
+  RETURN
+ELSEIF (KN == 1) THEN
+  FUNC= Z1
+  RETURN
+ELSE
+  DO J=2,KN
+    Z2= Z0+Z1
+    Z0= Z1
+    Z1= Z2
+  ENDDO
+  FUNC= Z2
+  RETURN
+ENDIF
+END FUNCTION FUNC
+    """.strip()
+
+    routine = Subroutine.from_source(fcode, frontend=frontend)
+    conditionals = FindNodes(Conditional).visit(routine.body)
+    assert len(conditionals) == 2
+    assert isinstance(conditionals[0].body[-1], Intrinsic)
+    assert conditionals[0].body[-1].text.upper() == 'RETURN'
+    assert conditionals[0].else_body == (conditionals[1],)
+    assert isinstance(conditionals[1].body[-1], Intrinsic)
+    assert conditionals[1].body[-1].text.upper() == 'RETURN'
+    assert isinstance(conditionals[1].else_body[-1], Intrinsic)
+    assert conditionals[1].else_body[-1].text.upper() == 'RETURN'