feat(generic): add simplified type inference mechanism ExpressionType…

…Mapper

loki/expression/mappers.py

@@ -29,7 +29,7 @@
 
 
 __all__ = ['LokiStringifyMapper', 'ExpressionRetriever', 'ExpressionDimensionsMapper',
-           'ExpressionCallbackMapper', 'SubstituteExpressionsMapper',
+           'ExpressionTypeMapper', 'ExpressionCallbackMapper', 'SubstituteExpressionsMapper',
            'LokiIdentityMapper', 'AttachScopesMapper', 'DetachScopesMapper']
 
 
@@ -426,6 +426,43 @@ def map_inline_do(self, expr, *args, **kwargs):
         return self.rec(expr.bounds, *args, **kwargs)
 
 
+class ExpressionTypeMapper(Mapper):
+    """
+    A visitor for an expression that determines the type of the expression.
+    This is a WIP implementation (missing, e.g.: handling of kinds, implicit type conversions)
+    """
+    # pylint: disable=abstract-method,unused-argument
+
+    def map_float_literal(self, expr, *args, **kwargs):
+        return BasicType.REAL
+
+    def map_int_literal(self, expr, *args, **kwargs):
+        return BasicType.INTEGER
+
+    def map_logic_literal(self, expr, *args, **kwargs):
+        return BasicType.LOGICAL
+
+    def map_string_literal(self, expr, *args, **kwargs):
+        return BasicType.CHARACTER
+
+    def map_scalar(self, expr, *args, **kwargs):
+        return expr.type.dtype
+
+    map_array = map_scalar
+
+    def map_sum(self, expr, *args, **kwargs):
+        left = self.rec(expr.children[0], *args, **kwargs)
+        right = self.rec(expr.children[1], *args, **kwargs)
+        # INTEGER can be promoted to REAL
+        if left == BasicType.REAL and right == BasicType.INTEGER \
+                or left == BasicType.INTEGER and right == BasicType.REAL:
+            return BasicType.REAL
+        if left != right:
+            raise ValueError(f'Non-matching types: {str(left)} and {str(right)}')
+        return left
+
+    map_product = map_sum
+
 class ExpressionCallbackMapper(CombineMapper):
     """
     A visitor for expressions that returns the combined result of a specified callback function.