Allow subscripts to have methods called (#2735)

* Add subscripts to callable types

* Add tests

* Remove C backend

Author: advikkabra

integration_tests/CMakeLists.txt

@@ -796,6 +796,7 @@ RUN(NAME generics_array_03   LABELS cpython llvm llvm_jit c)
 RUN(NAME generics_list_01    LABELS cpython llvm llvm_jit c)
 RUN(NAME test_statistics_01  LABELS cpython llvm llvm_jit NOFAST)
 RUN(NAME test_statistics_02  LABELS cpython llvm llvm_jit NOFAST REQ_PY_VER 3.10)
+RUN(NAME test_attributes     LABELS cpython llvm llvm_jit)
 RUN(NAME test_str_attributes LABELS cpython llvm llvm_jit c)
 RUN(NAME kwargs_01           LABELS cpython llvm llvm_jit c NOFAST)
 RUN(NAME def_func_01         LABELS cpython llvm llvm_jit c)

integration_tests/test_attributes.py

@@ -0,0 +1,12 @@
+def test_attributes() -> None:
+    a: i32 = 10
+    assert a.bit_length() == 4
+
+    b: str = 'abc'
+    assert b.upper() == 'ABC'
+
+    c: list[i32] = [10, 20, 30]
+    assert c[0].bit_length() == 4
+    assert c.index(10) == 0
+
+test_attributes()

src/lpython/semantics/python_ast_to_asr.cpp

@@ -8040,6 +8040,17 @@ we will have to use something else.
             }
             handle_builtin_attribute(dict_expr, at->m_attr, loc, eles);
             return;
+        } else if (AST::is_a<AST::Subscript_t>(*at->m_value)) {
+            AST::Subscript_t *s = AST::down_cast<AST::Subscript_t>(at->m_value);
+            visit_Subscript(*s);
+            ASR::expr_t *subscript_expr =  ASR::down_cast<ASR::expr_t>(tmp);
+            Vec<ASR::expr_t*> eles;
+            eles.reserve(al, args.size());
+            for (size_t i = 0; i < args.size(); i++) {
+                eles.push_back(al, args[i].m_value);
+            }
+            handle_builtin_attribute(subscript_expr, at->m_attr, loc, eles);
+            return;
         } else {
             throw SemanticError("Only Name type and constant integers supported in Call", loc);
         }