Merge pull request #878 from namannimmo10/str_assign

Raise error while changing immutable objects

Author: namannimmo10

src/libasr/asr_utils.h

@@ -809,6 +809,11 @@ static inline std::string binop_to_str_python(const ASR::binopType t) {
     }
 }
 
+static inline bool is_immutable(const ASR::ttype_t *type) {
+    return ((ASR::is_a<ASR::Character_t>(*type) || ASR::is_a<ASR::Tuple_t>(*type)
+        || ASR::is_a<ASR::Complex_t>(*type)));
+}
+
 // Returns a list of values
 static inline Vec<ASR::call_arg_t> get_arg_values(Allocator &al, const Vec<ASR::call_arg_t>& args) {
     Vec<ASR::call_arg_t> values;

src/lpython/semantics/python_ast_to_asr.cpp

@@ -2588,6 +2588,24 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
                                 ASR::make_Var_t(al, x.base.base.loc, s));
                         tmp = make_DictInsert_t(al, x.base.base.loc, se, key, val);
                         return;
+                    } else if (ASRUtils::is_immutable(type)) {
+                        throw SemanticError("'" + ASRUtils::type_to_str_python(type) + "' object does not support"
+                            " item assignment", x.base.base.loc);
+                    }
+                }
+            } else if (AST::is_a<AST::Attribute_t>(*x.m_targets[0])) {
+                AST::Attribute_t *attr = AST::down_cast<AST::Attribute_t>(x.m_targets[0]);
+                if (AST::is_a<AST::Name_t>(*attr->m_value)) {
+                    std::string name = AST::down_cast<AST::Name_t>(attr->m_value)->m_id;
+                    ASR::symbol_t *s = current_scope->get_symbol(name);
+                    if (!s) {
+                        throw SemanticError("Variable: '" + name + "' is not declared",
+                                x.base.base.loc);
+                    }
+                    ASR::Variable_t *v = ASR::down_cast<ASR::Variable_t>(s);
+                    ASR::ttype_t *type = v->m_type;
+                    if (ASRUtils::is_immutable(type)) {
+                        throw SemanticError("readonly attribute", x.base.base.loc);
                     }
                 }
             }

tests/errors/test_assign6.py

@@ -0,0 +1,6 @@
+def f():
+    s: str
+    s = "abcde"
+    s[0] = 'f'
+
+f()

tests/errors/test_assign7.py

@@ -0,0 +1,6 @@
+def f():
+    t: tuple[i32, i32]
+    t = (1, 2)
+    t[0] = 3
+
+f()

tests/errors/test_assign8.py

@@ -0,0 +1,6 @@
+def f():
+    c: c32
+    c = complex(3, 4)
+    c.real = 5.0
+
+f()

tests/reference/asr-test_assign6-05cd64f.json

@@ -0,0 +1,13 @@
+{
+    "basename": "asr-test_assign6-05cd64f",
+    "cmd": "lpython --show-asr --no-color {infile} -o {outfile}",
+    "infile": "tests/errors/test_assign6.py",
+    "infile_hash": "6837d07201b8680dbb63908d3ad27e4e9bfb1f1ff77b4bd6a77eddcf",
+    "outfile": null,
+    "outfile_hash": null,
+    "stdout": null,
+    "stdout_hash": null,
+    "stderr": "asr-test_assign6-05cd64f.stderr",
+    "stderr_hash": "294865737572b9ab043b8ebab73fe949fa2bb73e9790c6a04d87dc50",
+    "returncode": 2
+}

tests/reference/asr-test_assign6-05cd64f.stderr

@@ -0,0 +1,5 @@
+semantic error: 'str' object does not support item assignment
+ --> tests/errors/test_assign6.py:4:5
+  |
+4 |     s[0] = 'f'
+  |     ^^^^^^^^^^ 

tests/reference/asr-test_assign7-beebac3.json

@@ -0,0 +1,13 @@
+{
+    "basename": "asr-test_assign7-beebac3",
+    "cmd": "lpython --show-asr --no-color {infile} -o {outfile}",
+    "infile": "tests/errors/test_assign7.py",
+    "infile_hash": "e54f67638add63131760d5eadda7e3944b34addacffa27d6fb45e128",
+    "outfile": null,
+    "outfile_hash": null,
+    "stdout": null,
+    "stdout_hash": null,
+    "stderr": "asr-test_assign7-beebac3.stderr",
+    "stderr_hash": "d12f04efad566740bd562fbe9c00a058210a9adf0f5297475fc41fe6",
+    "returncode": 2
+}

tests/reference/asr-test_assign7-beebac3.stderr

@@ -0,0 +1,5 @@
+semantic error: 'tuple[i32, i32]' object does not support item assignment
+ --> tests/errors/test_assign7.py:4:5
+  |
+4 |     t[0] = 3
+  |     ^^^^^^^^ 

tests/reference/asr-test_assign8-4b26e63.json

@@ -0,0 +1,13 @@
+{
+    "basename": "asr-test_assign8-4b26e63",
+    "cmd": "lpython --show-asr --no-color {infile} -o {outfile}",
+    "infile": "tests/errors/test_assign8.py",
+    "infile_hash": "c88b84b8d7d21aec489288c9064cc9d5a46387b5e6528d30a947ff5c",
+    "outfile": null,
+    "outfile_hash": null,
+    "stdout": null,
+    "stdout_hash": null,
+    "stderr": "asr-test_assign8-4b26e63.stderr",
+    "stderr_hash": "d3f4498398b59be4a1f83de67135842aa5a9a0921e1aa188dc743ca8",
+    "returncode": 2
+}