added simple lifetime check

toy-impl/examples/a.py

@@ -1,30 +1,65 @@
-I = TypeVar('I', int32, float, Vec)
+T = TypeVar('T')
 
-class Vec:
+class Foo:
-    v: list[int32]
+    a: list[int32]
-    def __init__(self, v: list[int32]):
+    b: list[int32]
-        self.v = v
 
-    def __add__(self, other: I) -> Vec:
+def choose(t: bool, a: T, b: T) -> T:
-        if type(other) == int32:
+    if t:
-            return Vec([v + other for v in self.v])
-        elif type(other) == float:
-            return Vec([v + int32(other) for v in self.v])
-        else:
-            return Vec([self.v[i] + other.v[i] for i in range(len(self.v))])
-
-    def get(self, index: int32) -> int32:
-        return self.v.head()
-
-
-T = TypeVar('T', int32, list[int32])
-
-def add(a: int32, b: T) -> int32:
-    if type(b) == int32:
-        return a + b
-    else:
-        for x in b:
-            a = add(a, x)
         return a
+    else:
+        return b
+
+def set_list(ls: list[T], a: T):
+    # this should fail
+    l2 = ls
+    l2[-1] = a
+
+def get_foo(a: Foo) -> list[int32]:
+    return a.a
+
+def set_foo(a: Foo, b: Foo):
+    a.a[0] = b.a[0]
+    if True:
+        c = b
+        # this should fail
+        c.a = a.a
+
+def set_foo2(a: Foo, b: Foo):
+    a.a[0] = b.a[0]
+    if True:
+        c = [Foo()]
+        c[0] = a
+        # this should fail
+        c[0].a = b.a
+
+def set_foo3(a: Foo, b: Foo):
+    a.a[0] = b.a[0]
+    if True:
+        c = [Foo()]
+        c[0] = a
+        # this should fail
+        c[0].a = get_foo(b)
+
+def set_foo4(a: Foo, b: Foo):
+    a.a[0] = b.a[0]
+    if True:
+        c = [Foo()]
+        d = c
+        d[0] = a
+        # this should fail
+        c[0].a = get_foo(b)
+
+def set_foo5(a: Foo, b: Foo):
+    a.a[0] = b.a[0]
+    if True:
+        c = [Foo()]
+        d = c
+        e = d
+        f = e
+        f[0] = a
+        # this should fail
+        c[0].a = get_foo(b)
+
 
 

toy-impl/lifetime.py

@@ -0,0 +1,86 @@
+import ast
+from type_def import PrimitiveType
+from parse_expr import parse_expr
+
+class Lifetime:
+    low: int
+    original: int
+
+    def __init__(self, scope):
+        self.low = self.original = scope
+        self.parent = None
+
+    def fold(self):
+        while self.parent is not None:
+            self.low = self.parent.low
+            self.original = self.parent.original
+            self.parent = self.parent.parent
+        return self
+
+    def ok(self, other):
+        self.fold()
+        if other == None:
+            return False
+        other.fold()
+        return self.low >= other.original and \
+            (other.original != self.low or self.low != 1)
+
+    def __str__(self):
+        self.fold()
+        return f'({self.low}, {self.original})'
+
+
+def assign_expr(
+        scope: int,
+        sym_table: dict[str, Lifetime],
+        expr: ast.expr):
+    if isinstance(expr, ast.Expression):
+        body = expr.body
+    else:
+        body = expr
+    if isinstance(body.type, PrimitiveType):
+        body.lifetime = None
+    elif isinstance(body, ast.Attribute):
+        body.lifetime = assign_expr(scope, sym_table, body.value)
+    elif isinstance(body, ast.Subscript):
+        body.lifetime = assign_expr(scope, sym_table, body.value)
+    elif isinstance(body, ast.Name):
+        if body.id in sym_table:
+            body.lifetime = sym_table[body.id]
+        else:
+            body.lifetime = Lifetime(scope)
+            sym_table[body.id] = body.lifetime
+    else:
+        body.lifetime = Lifetime(scope)
+    return body.lifetime
+
+
+def assign_stmt(
+        scope: int,
+        sym_table: dict[str, Lifetime],
+        nodes):
+    for node in nodes:
+        if isinstance(node, ast.Assign):
+            b = assign_expr(scope, sym_table, node.value)
+            for target in node.targets:
+                a = assign_expr(scope, sym_table, target)
+                if a == None and b == None:
+                    continue
+                if not a.ok(b):
+                    print(ast.unparse(node))
+                    print(f'{a} <- {b}')
+                    assert False
+                a.low = min(a.low, b.low)
+                a.original = max(a.original, b.original)
+                b.parent = a
+        elif isinstance(node, ast.If) or isinstance(node, ast.While):
+            assign_stmt(scope + 1, sym_table, node.body)
+            assign_stmt(scope + 1, sym_table, node.orelse)
+        elif isinstance(node, ast.Return):
+            a = assign_expr(scope, sym_table, node.value)
+            if a != None and a.fold().original > 1:
+                print(ast.unparse(node))
+                print(a)
+                assert False
+
+

toy-impl/main.py

@@ -7,6 +7,7 @@ from parse_stmt import parse_stmts
 from primitives import simplest_ctx
 from top_level import parse_top_level
 from inheritance import class_fixup
+from lifetime import Lifetime, assign_stmt
 
 if len(sys.argv)  != 2:
     print('please pass the python script name as argument')
@@ -40,9 +41,20 @@ try:
             if isinstance(ty, SelfType):
                 ty = ctx.types[c]
             sym_table[n.arg] = ty.subst(subst)
-        _, _, returned = parse_stmts(ctx, sym_table, sym_table, result, fn.body)
+        try:
-        if result is not None and not returned:
+            print()
-            raise CustomError('Function may have no return value', fn)
+            print('checking:')
+            print(ast.unparse(fn))
+            print('typecheck...')
+            _, _, returned = parse_stmts(ctx, sym_table, sym_table, result, fn.body)
+            if result is not None and not returned:
+                raise CustomError('Function may have no return value', fn)
+            print('lifetime check...')
+            sym_table = {k: Lifetime(1) for k in sym_table}
+            assign_stmt(2, sym_table, fn.body)
+            print('OK!')
+        except AssertionError:
+            pass
 except CustomError as e:
     print('Error while type checking:')
     print(e.msg)

toy-impl/parse_expr.py

@@ -17,33 +17,35 @@ def parse_expr(ctx: Context,
     else:
         body = expr
     if isinstance(body, ast.Constant):
-        return parse_constant(ctx, sym_table, body)
+        result = parse_constant(ctx, sym_table, body)
-    if isinstance(body, ast.UnaryOp):
+    elif isinstance(body, ast.UnaryOp):
-        return parse_unary_ops(ctx, sym_table, body)
+        result = parse_unary_ops(ctx, sym_table, body)
-    if isinstance(body, ast.BinOp):
+    elif isinstance(body, ast.BinOp):
-        return parse_bin_ops(ctx, sym_table, body)
+        result = parse_bin_ops(ctx, sym_table, body)
-    if isinstance(body, ast.Name):
+    elif isinstance(body, ast.Name):
-        return parse_name(ctx, sym_table, body)
+        result = parse_name(ctx, sym_table, body)
-    if isinstance(body, ast.List):
+    elif isinstance(body, ast.List):
-        return parse_list(ctx, sym_table, body)
+        result = parse_list(ctx, sym_table, body)
-    if isinstance(body, ast.Tuple):
+    elif isinstance(body, ast.Tuple):
-        return parse_tuple(ctx, sym_table, body)
+        result = parse_tuple(ctx, sym_table, body)
-    if isinstance(body, ast.Attribute):
+    elif isinstance(body, ast.Attribute):
-        return parse_attribute(ctx, sym_table, body)
+        result = parse_attribute(ctx, sym_table, body)
-    if isinstance(body, ast.BoolOp):
+    elif isinstance(body, ast.BoolOp):
-        return parse_bool_ops(ctx, sym_table, body)
+        result = parse_bool_ops(ctx, sym_table, body)
-    if isinstance(body, ast.Compare):
+    elif isinstance(body, ast.Compare):
-        return parse_compare(ctx, sym_table, body)
+        result = parse_compare(ctx, sym_table, body)
-    if isinstance(body, ast.Call):
+    elif isinstance(body, ast.Call):
-        return parse_call(ctx, sym_table, body)
+        result = parse_call(ctx, sym_table, body)
-    if isinstance(body, ast.Subscript):
+    elif isinstance(body, ast.Subscript):
-        return parse_subscript(ctx, sym_table, body)
+        result = parse_subscript(ctx, sym_table, body)
-    if isinstance(body, ast.IfExp):
+    elif isinstance(body, ast.IfExp):
-        return parse_if_expr(ctx, sym_table, body)
+        result = parse_if_expr(ctx, sym_table, body)
-    if isinstance(body, ast.ListComp):
+    elif isinstance(body, ast.ListComp):
-        return parse_list_comprehension(ctx, sym_table, body)
+        result = parse_list_comprehension(ctx, sym_table, body)
-    raise CustomError(f'{body} is not yet supported', body)
+    else:
-
+        raise CustomError(f'{body} is not yet supported', body)
+    body.type = result
+    return result
 
 def get_unary_op(op):
     if isinstance(op, ast.UAdd):
@@ -238,6 +240,7 @@ def parse_simple_binding(name, ty):
     if isinstance(name, ast.Name):
         if name.id == '_':
             return {}
+        name.type = ty
         return {name.id: ty}
     elif isinstance(name, ast.Tuple):
         if not isinstance(ty, TupleType):

toy-impl/parse_stmt.py

@@ -50,15 +50,18 @@ def get_target_type(ctx: Context,
         i = parse_expr(ctx, sym_table, target.slice)
         if i != ctx.types['int32']:
             raise CustomError(f'index must be int32', target.slice)
+        target.type = t.params[0]
         return t.params[0]
     elif isinstance(target, ast.Attribute):
         t = get_target_type(ctx, sym_table, used_sym_table, target.value)
         if target.attr not in t.fields:
             raise CustomError(f'{t} has no field {target.attr}', target)
+        target.type = t.fields[target.attr]
         return t.fields[target.attr]
     elif isinstance(target, ast.Name):
         if target.id not in sym_table:
             raise CustomError(f'unbounded {target.id}', target)
+        target.type = sym_table[target.id]
         return sym_table[target.id]
     else:
         raise CustomError(f'assignment to {target} is not supported', target)
@@ -76,6 +79,7 @@ def parse_stmt_binding(ctx: Context,
                                   f'but is now {ty}', target)
         if target.id == '_':
             return {}
+        target.type = ty
         return {target.id: ty}
     elif isinstance(target, ast.Tuple):
         if not isinstance(ty, TupleType):