Error on assignment to function parameter

integration_tests/generics_02.py

@@ -1,13 +1,13 @@
-from lpython import TypeVar
+from lpython import TypeVar, InOut
 
 T = TypeVar('T')
 
-def swap(x: T, y: T):
+def swap(x: InOut[T], y: InOut[T]):
     temp: T
     temp = x
     x = y
     y = temp
     print(x)
     print(y)
 
-swap(1,2)
+swap(1,2)

src/lpython/semantics/python_ast_to_asr.cpp

@@ -4844,6 +4844,13 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
                     std::string var_name = std::string(v->m_name);
                     throw SemanticError("Assignment to loop variable `" + std::string(to_lower(var_name)) +"` is not allowed", target->base.loc);
                 }
+                if (sym->type == ASR::symbolType::Variable) {
+                    ASR::Variable_t *v = ASR::down_cast<ASR::Variable_t>(sym);
+                    if (v->m_intent == ASR::intentType::In) {
+                        throw SemanticError("Assignment to an input function parameter `"
+                            + std::string(v->m_name) + "` is not allowed", target->base.loc);
+                    }
+                }
             }
             tmp_vec.push_back(ASR::make_Assignment_t(al, x.base.base.loc, target, tmp_value,
                                     overloaded));

src/runtime/lpython_builtin.py

@@ -198,18 +198,20 @@ def bin(n: i32) -> str:
         return '0b0'
     prep: str
     prep = '0b'
-    if n < 0:
-        n = -n
+    n_: i32
+    n_ = n
+    if n_ < 0:
+        n_ = -n_
         prep = '-0b'
     res: str
     res = ''
-    if (n - _lpython_floordiv(n, 2)*2) == 0:
+    if (n_ - _lpython_floordiv(n_, 2)*2) == 0:
         res += '0'
     else:
         res += '1'
-    while n > 1:
-        n = _lpython_floordiv(n, 2)
-        if (n - _lpython_floordiv(n, 2)*2) == 0:
+    while n_ > 1:
+        n_ = _lpython_floordiv(n_, 2)
+        if (n_ - _lpython_floordiv(n_, 2)*2) == 0:
             res += '0'
         else:
             res += '1'
@@ -227,16 +229,18 @@ def hex(n: i32) -> str:
         return '0x0'
     prep: str
     prep = '0x'
-    if n < 0:
+    n_: i32
+    n_ = n
+    if n_ < 0:
         prep = '-0x'
-        n = -n
+        n_ = -n_
     res: str
     res = ""
     remainder: i32
-    while n > 0:
-        remainder = n - _lpython_floordiv(n, 16)*16
-        n -= remainder
-        n = _lpython_floordiv(n, 16)
+    while n_ > 0:
+        remainder = n_ - _lpython_floordiv(n_, 16)*16
+        n_ -= remainder
+        n_ = _lpython_floordiv(n_, 16)
         res += hex_values[remainder]
     return prep + res[::-1]
 
@@ -252,16 +256,18 @@ def oct(n: i32) -> str:
         return '0o0'
     prep: str
     prep = '0o'
-    if n < 0:
+    n_: i32
+    n_ = n
+    if n_ < 0:
         prep = '-0o'
-        n = -n
+        n_ = -n_
     res: str
     res = ""
     remainder: i32
-    while n > 0:
-        remainder = n - _lpython_floordiv(n, 8)*8
-        n -= remainder
-        n = _lpython_floordiv(n, 8)
+    while n_ > 0:
+        remainder = n_ - _lpython_floordiv(n_, 8)*8
+        n_ -= remainder
+        n_ = _lpython_floordiv(n_, 8)
         res += _values[remainder]
     return prep + res[::-1]
 
@@ -805,18 +811,18 @@ def _lpython_str_startswith(s: str ,sub: str) -> bool:
     return res
 
 @overload
-def _lpython_str_endswith(s: str, suffix: str) -> bool: 
+def _lpython_str_endswith(s: str, suffix: str) -> bool:
 
     if(len(suffix) > len(s)):
         return False
-    
+
     i : i32
     i = 0
     while(i < len(suffix)):
         if(suffix[len(suffix) - i - 1] != s[len(s) - i - 1]):
             return False
         i += 1
-        
+
     return True
 
 @overload
@@ -833,13 +839,13 @@ def _lpython_str_partition(s:str, sep: str) -> tuple[str, str, str]:
     ind = _lpython_str_find(s, sep)
     if ind == -1:
         res = (s, "", "")
-    else: 
-        res = (s[0:ind], sep, s[ind+len(sep): len(s)])    
+    else:
+        res = (s[0:ind], sep, s[ind+len(sep): len(s)])
     return res
 
 @overload
 def _lpython_str_islower(s: str) -> bool:
-    is_cased_present: bool 
+    is_cased_present: bool
     is_cased_present = False
     i:str
     for i in s:
@@ -851,7 +857,7 @@ def _lpython_str_islower(s: str) -> bool:
 
 @overload
 def _lpython_str_isupper(s: str) -> bool:
-    is_cased_present: bool 
+    is_cased_present: bool
     is_cased_present = False
     i:str
     for i in s:

src/runtime/math.py

@@ -472,29 +472,37 @@ def gcd(a: i32, b: i32) -> i32:
     Returns greatest common divisor of `a` and `b`
     """
     temp: i32
-    if a < 0:
-        a = -a
-    if b < 0:
-        b = -b
-    while b != 0:
-        a = mod(a, b)
-        temp = a
-        a = b
-        b = temp
-    return a
+    a_: i32
+    b_: i32
+    a_ = a
+    b_ = b
+    if a_ < 0:
+        a_ = -a_
+    if b_ < 0:
+        b_ = -b_
+    while b_ != 0:
+        a_ = mod(a_, b_)
+        temp = a_
+        a_ = b_
+        b_ = temp
+    return a_
 
 
 def lcm(a: i32, b: i32) -> i32:
     """
     Returns least common multiple of `a` and `b`
     """
-    if a < 0:
-        a = -a
-    if b < 0:
-        b = -b
-    if a*b == 0:
+    a_: i32
+    b_: i32
+    a_ = a
+    b_ = b
+    if a_ < 0:
+        a_ = -a_
+    if b_ < 0:
+        b_ = -b_
+    if a_*b_ == 0:
         return 0
-    return i32(floor((a*b)/gcd(a, b)))
+    return i32(floor((a_*b_)/gcd(a_, b_)))
 
 
 def copysign(x: f64, y: f64) -> f64:

tests/errors/test_assign9.py

@@ -0,0 +1,5 @@
+def f(x: i32) -> i32:
+    x = 2
+    return x * x
+
+print(f(3)) # => 4

tests/expr9.py

@@ -11,20 +11,14 @@ def test_return_2(a: i32) -> str:
 
 
 def test_return_3(a: i32) -> i32:
-    a = 3
     return a
 
 
-def test_return_4(a: i32):
-    a = 1
-    return
-
 def main0():
     i: i32
     i = test_return_1(4)
     s: str
     s = test_return_2(4)
     i = test_return_3(4)
-    test_return_4(4)
 
 main0()

tests/reference/asr-expr9-814e4bc.json

@@ -2,11 +2,11 @@
     "basename": "asr-expr9-814e4bc",
     "cmd": "lpython --show-asr --no-color {infile} -o {outfile}",
     "infile": "tests/expr9.py",
-    "infile_hash": "1f02a7486b298ae9e74a163875a76f8fa7cc25d7f50547133dbbdfab",
+    "infile_hash": "4819e0f20d2ed25647ab94f74cb7b5b61e3d4f43e159e46ad79c1c4c",
     "outfile": null,
     "outfile_hash": null,
     "stdout": "asr-expr9-814e4bc.stdout",
-    "stdout_hash": "fd9a9323419a77d41f2b3b06c607be0aab4dc626a070dda593b2117c",
+    "stdout_hash": "b1daccda9413a8fc6ad88b8898e011d5f556e862f9b853b3564d7189",
     "stderr": null,
     "stderr_hash": null,
     "returncode": 0