#2105 Fix temporary variables with wrong type

src/psyclone/psyir/transformations/intrinsics/array_reduction_base_trans.py

@@ -43,7 +43,7 @@
 from psyclone.psyir.nodes import (
     Assignment, Reference, ArrayReference, IfBlock, Loop,
     IntrinsicCall, Node, UnaryOperation, BinaryOperation)
-from psyclone.psyir.symbols import ArrayType, DataSymbol
+from psyclone.psyir.symbols import ArrayType, DataSymbol, ScalarType
 from psyclone.psyGen import Transformation
 from psyclone.psyir.transformations.reference2arrayrange_trans import \
     Reference2ArrayRangeTrans
@@ -170,6 +170,19 @@ def validate(self, node, options=None):
                         f"Unexpected shape for array. Expecting one of "
                         f"Deferred, Attribute or Bounds but found '{shape}'.")
 
+        # If the lhs symbol is used anywhere on the assignment rhs, we need
+        # to create a temporary, and for this we need to resolve its datatype
+        for rhs_reference in assignment.rhs.walk(Reference):
+            if rhs_reference.symbol is assignment.lhs.symbol:
+                if not (isinstance(assignment.lhs.symbol, DataSymbol) and
+                        isinstance(assignment.lhs.datatype, ScalarType)):
+                    line = assignment.debug_string().strip('\n')
+                    raise TransformationError(
+                        f"To loopify '{line}'"
+                        f" we need a temporary variable, but the type of "
+                        f"'{assignment.lhs.debug_string()}' can not be "
+                        f"resolved or is unsupported.")
+
     # pylint: disable=too-many-locals
     def apply(self, node, options=None):
         '''Apply the array-reduction intrinsic conversion transformation to
@@ -199,7 +212,7 @@ def apply(self, node, options=None):
         if increment:
             new_lhs_symbol = node.scope.symbol_table.new_symbol(
                 root_name="tmp_var", symbol_type=DataSymbol,
-                datatype=lhs_symbol.datatype)
+                datatype=orig_lhs.datatype)
             new_lhs = Reference(new_lhs_symbol)
         else:
             new_lhs = orig_lhs.copy()

src/psyclone/tests/psyir/transformations/intrinsics/array_reduction_base_trans_test.py

@@ -235,6 +235,27 @@ def test_not_assignment(fortran_reader):
             "of an Assignment" in str(info.value))
 
 
+def test_validate_increment_with_unsupported_type(fortran_reader):
+    '''Check that the expected error is produced when the resulting code
+    needs a temporary variable but the lhs type can not be resolved.
+
+    '''
+    code = (
+        "subroutine test()\n"
+        "use othermod\n"
+        "real :: a(10)\n"
+        "x(1) = x(1) + maxval(a)\n"
+        "end subroutine\n")
+    psyir = fortran_reader.psyir_from_source(code)
+    trans = Maxval2LoopTrans()
+    node = psyir.walk(IntrinsicCall)[0]
+    with pytest.raises(TransformationError) as info:
+        trans.apply(node)
+    assert ("To loopify 'x(1) = x(1) + MAXVAL(a)' we need a temporary "
+            "variable, but the type of 'x(1)' can not be resolved or is "
+            "unsupported." in str(info.value))
+
+
 # apply
 
 @pytest.mark.parametrize("idim1,idim2,rdim11,rdim12,rdim21,rdim22",
@@ -648,10 +669,38 @@ def test_increment(fortran_reader, fortran_writer, tmpdir):
     assert Compile(tmpdir).string_compiles(result)
 
 
-def test_reduce_to_struct_and_array_accessors(fortran_reader, fortran_writer,
-                                              tmpdir):
+def test_increment_with_accessor(fortran_reader, fortran_writer, tmpdir):
     '''Check that the expected code is produced when the variable being
-    assigned to is an increment e.g. x = x + ...
+    assigned needs a temporary variable that is not the same type as the
+    lhs symbol because some accessor expression is used.
+
+    '''
+    code = (
+        "subroutine test()\n"
+        "real :: a(10)\n"
+        "real, dimension(1) :: x\n"
+        "x(1) = x(1) + maxval(a)\n"
+        "end subroutine\n")
+    expected_decl = "real :: tmp_var"
+    expected = (
+        "  tmp_var = -HUGE(tmp_var)\n"
+        "  do idx = 1, 10, 1\n"
+        "    tmp_var = MAX(tmp_var, a(idx))\n"
+        "  enddo\n"
+        "  x(1) = x(1) + tmp_var\n")
+    psyir = fortran_reader.psyir_from_source(code)
+    trans = Maxval2LoopTrans()
+    node = psyir.walk(IntrinsicCall)[0]
+    trans.apply(node)
+    result = fortran_writer(psyir)
+    assert expected_decl in result
+    assert expected in result
+    assert Compile(tmpdir).string_compiles(result)
+
+
+def test_reduce_to_struct_and_array_accessors(fortran_reader, fortran_writer):
+    '''Check that the expected code is produced when the variable being
+    assigned to is has array and structure accessors.
 
     '''
     code = (
@@ -671,7 +720,6 @@ def test_reduce_to_struct_and_array_accessors(fortran_reader, fortran_writer,
     trans.apply(node)
     result = fortran_writer(psyir)
     assert expected in result
-    assert Compile(tmpdir).string_compiles(result)
 
 
 def test_range2loop_fails(fortran_reader, fortran_writer):