Enabled accessing base class members from derived class

Author: tanay-man

integration_tests/CMakeLists.txt

@@ -839,6 +839,7 @@ RUN(NAME class_01          LABELS cpython llvm llvm_jit)
 RUN(NAME class_02          LABELS cpython llvm llvm_jit)
 RUN(NAME class_03          LABELS cpython llvm llvm_jit)
 RUN(NAME class_04          LABELS cpython llvm llvm_jit)
+RUN(NAME class_05          LABELS cpython llvm llvm_jit)
 
 # callback_04 is to test emulation. So just run with cpython
 RUN(NAME callback_04       IMPORT_PATH .. LABELS cpython)

integration_tests/class_05.py

@@ -1,18 +1,32 @@
 from lpython import i32
 
-class Base:
-    def __init__(self:"Base"):
-        self.x_A : i32 = 10
+class Animal:
+    def __init__(self:"Animal"):
+        self.species: str = "Generic Animal"
+        self.age: i32 = 0
+
+class Dog(Animal):
+    def __init__(self:"Dog", name:str, age:i32):
+        # super().__init__()
+        self.species: str = "Dog"
+        self.name: str = name
+        self.age: i32 = age
+
+class Cat(Animal):
+    def __init__(self:"Cat", name: str, age: i32):
+        # super().__init__()
+        self.species: str = "Cat"
+        self.name:str = name
+        self.age: i32 = age
 
-class Derived(Base):
-    def __init__(self:"Derived") :
-        super().__init__()
-        self.y_B : i32 = 6
-    def get_x_A(self:"Derived"):
-        print(self.x_A)
 def main():
-    d : Derived = Derived()
-    print(d.x_A)
-    print(d.y_B)
-    d.get_x_A()
+    dog: Dog = Dog("Buddy", 5)
+    cat: Cat = Cat("Whiskers", 3)
+    op1: str = str(dog.name+" is a "+str(dog.age)+"-year-old "+dog.species+".")
+    print(op1)
+    assert op1 == "Buddy is a 5-year-old Dog."
+    op2: str = str(cat.name+ " is a "+ str(cat.age)+ "-year-old "+ cat.species+ ".")
+    print(op2)
+    assert op2 == "Whiskers is a 3-year-old Cat."
+
 main()

src/lpython/semantics/python_ast_to_asr.cpp

@@ -3301,10 +3301,21 @@ class CommonVisitor : public AST::BaseVisitor<Struct> {
                 current_scope->add_symbol(x_m_name, class_type);
             }
         } else {
-            if( x.n_bases > 0 ) {
-                throw SemanticError("Inheritance in classes isn't supported yet.",
+            ASR::symbol_t* parent = nullptr;
+            if( x.n_bases > 1 ) {
+                throw SemanticError("Multiple inheritance in classes isn't supported yet.",
                                     x.base.base.loc);
             }
+            else if (x.n_bases == 1) {
+                AST::Name_t* n = nullptr;
+                if ( AST::is_a<AST::Name_t>(*x.m_bases[0]) ) {
+                    n = AST::down_cast<AST::Name_t>(x.m_bases[0]);
+                } else {
+                    throw SemanticError("Expected a Name here",x.base.base.loc);
+                }
+                parent = current_scope->resolve_symbol(n->m_id);
+                LCOMPILERS_ASSERT(ASR::is_a<ASR::Struct_t>(*parent));
+            }
             SymbolTable *parent_scope = current_scope;
             if( ASR::symbol_t* sym = current_scope->resolve_symbol(x_m_name) ) {
                 LCOMPILERS_ASSERT(ASR::is_a<ASR::Struct_t>(*sym));
@@ -3324,6 +3335,15 @@ class CommonVisitor : public AST::BaseVisitor<Struct> {
                 }
             } else {
                 current_scope = al.make_new<SymbolTable>(parent_scope);
+                // if ( parent ) {
+                //     ASR::Struct_t* base_st = ASR::down_cast<ASR::Struct_t>(parent);
+                //     SymbolTable* base_scope = base_st->m_symtab;
+                //     for (auto i : base_scope->scope) {
+                //         std::string name = i.first;
+                //         ASR::symbol_t* sym = i.second;
+                //         current_scope->add_symbol(name,sym);
+                //     }
+                // }
                 Vec<char*> member_names;
                 Vec<char*> member_fn_names;
                 Vec<ASR::call_arg_t> member_init;
@@ -3344,7 +3364,7 @@ class CommonVisitor : public AST::BaseVisitor<Struct> {
                     member_names.p, member_names.size(), member_fn_names.p,
                     member_fn_names.size(), class_abi, ASR::accessType::Public,
                     false, false, member_init.p, member_init.size(),
-                    nullptr, nullptr));
+                    nullptr, parent));
                 parent_scope->add_symbol(x.m_name, class_sym);
                 visit_ClassMembers(x, member_names, member_fn_names,
                     struct_dependencies, member_init, false, class_abi, true);
@@ -6239,10 +6259,14 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
             for( size_t i = 0; i < der_type->n_members && !member_found; i++ ) {
                 member_found = std::string(der_type->m_members[i]) == member_name;
             }
-            if( !member_found ) {
+            if( !member_found && !der_type->m_parent ) {
                 throw SemanticError("No member " + member_name +
                                     " found in " + std::string(der_type->m_name),
                                     loc);
+            } else if ( !member_found && der_type->m_parent ) {
+                ASR::ttype_t* parent_type = ASRUtils::TYPE(ASRUtils::make_StructType_t_util(al, loc,der_type->m_parent));
+                visit_AttributeUtil(parent_type,attr_char,t,loc);
+                return;
             }
             ASR::expr_t *val = ASR::down_cast<ASR::expr_t>(ASR::make_Var_t(al, loc, t));
             ASR::symbol_t* member_sym = der_type->m_symtab->resolve_symbol(member_name);