allow eagerly eval global attr (#278)

I know this has been annoying. See the test for an example. I think this
should be considered a bug, although it still worth discussion on how
far do we allow eagerly evaluation on expressions involves global value
access, e.g `glob[1]` does not make sense in this case?

Author: Roger-luo

src/kirin/dialects/py/attr.py

@@ -40,10 +40,19 @@ class Lowering(lowering.FromPythonAST):
     def lower_Attribute(
         self, state: lowering.LoweringState, node: ast.Attribute
     ) -> lowering.Result:
+        from kirin.dialects.py import Constant
+
         if not isinstance(node.ctx, ast.Load):
             raise exceptions.DialectLoweringError(
                 f"unsupported attribute context {node.ctx}"
             )
+
+        # NOTE: eagerly load global variables
+        value = state.get_global_nothrow(node)
+        if value is not None:
+            stmt = state.append_stmt(Constant(value.unwrap()))
+            return lowering.Result(stmt)
+
         value = state.visit(node.value).expect_one()
         stmt = GetAttr(obj=value, attrname=node.attr)
         state.append_stmt(stmt)

test/program/py/test_glob_pi.py

@@ -0,0 +1,14 @@
+import math
+
+from kirin.prelude import basic_no_opt
+from kirin.dialects import py
+
+
+def test_math_pi():
+    @basic_no_opt
+    def main():
+        return math.pi
+
+    stmt = main.callable_region.blocks[0].stmts.at(0)
+    assert isinstance(stmt, py.Constant)
+    assert stmt.value == math.pi