fix: added initial implementation for supporting internal function definitions (#2119)

Author: arteevraina

integration_tests/CMakeLists.txt

@@ -671,6 +671,7 @@ RUN(NAME func_static_01 LABELS cpython llvm c wasm)
 RUN(NAME func_static_02 LABELS cpython llvm c wasm)
 RUN(NAME func_dep_03    LABELS cpython llvm c)
 RUN(NAME func_dep_04    LABELS cpython llvm c)
+RUN(NAME func_internal_def_01 LABELS cpython llvm NOFAST)
 
 RUN(NAME float_01 LABELS cpython llvm c wasm wasm_x64)
 RUN(NAME recursive_01 LABELS cpython llvm c wasm wasm_x64 wasm_x86)

integration_tests/func_internal_def_01.py

@@ -0,0 +1,11 @@
+def main():
+    x: i32
+    x = (2+3)*5
+    print(x)
+
+    def bar():
+        assert x == 25
+        
+    bar()
+
+main()

src/lpython/semantics/python_ast_to_asr.cpp

@@ -4060,6 +4060,24 @@ class SymbolTableVisitor : public CommonVisitor<SymbolTableVisitor> {
         return nullptr;
     }
 
+    // Implement visit_While for Symbol Table visitor.
+    void visit_While(const AST::While_t &/*x*/) {}
+
+    // Implement visit_Delete for Symbol Table visitor.
+    void visit_Delete(const AST::Delete_t &/*x*/) {}
+
+    // Implement visit_Pass for Symbol Table visitor.
+    void visit_Pass(const AST::Pass_t &/*x*/) {}
+
+    // Implement visit_Return for Symbol Table visitor.
+    void visit_Return(const AST::Return_t &/*x*/) {}
+
+    // Implement visit_Raise for Symbol Table visitor.
+    void visit_Raise(const AST::Raise_t &/*x*/) {}
+
+    // Implement visit_Global for Symbol Table visitor.
+    void visit_Global(const AST::Global_t &/*x*/) {}
+
     void visit_FunctionDef(const AST::FunctionDef_t &x) {
         dependencies.clear(al);
         SymbolTable *parent_scope = current_scope;
@@ -4304,6 +4322,12 @@ class SymbolTableVisitor : public CommonVisitor<SymbolTableVisitor> {
             }
         } else {
             bool is_pure = false, is_module = false;
+            
+            // This checks for internal function defintions as well.
+            for (size_t i = 0; i < x.n_body; i++) {
+                visit_stmt(*x.m_body[i]);
+            }
+            
             tmp = ASRUtils::make_Function_t_util(
                 al, x.base.base.loc,
                 /* a_symtab */ current_scope,