def infer_Tuple_expr(tup, env):
"""
Determine the type of AST `Tuple` expression under type environment `env`.
`ast.Tuple`
- `elts`: Python list of contained expr nodes
- `ctx`: context of the expr (e.g., load, store)
"""
assert tup.__class__ is ast.Tuple
elts_list = tup.elts
if all(infer_expr(e, env) != None for e in elts_list):
# (tup) assignment rule.
return PType.tuple([infer_expr(e, env) for e in elts_list])
else:
# No assignment rule found.
return None
def infer_Subscript_expr(subs, env):
"""
Determine the type of AST `Subscript` expression under type environment
`env`.
`ast.Subscript`
- `value`: the collection being subscripted
- `slice`: `ast.Index` or `ast.Slice`
+ `value`: expr used as index (if `ast.Index`)
+ `lower`: expr used as lower bound (if `ast.Slice`)
+ `upper`: expr used as upper bound (if `ast.Slice`)
+ `step`: expr used as step (if `ast.Slice`)
We can only subscript tuples with numeric literals because the inference
algorithm needs to actually know the values of the subscript parameters.
"""
assert subs.__class__ is ast.Subscript
col = subs.value
col_t = infer_expr(col, env)
is_index = subs.slice.__class__ is ast.Index
is_slice = subs.slice.__class__ is ast.Slice
assert is_index or is_slice
# Store the attributes of the slice.
if is_index:
i = subs.slice.value
else: # is_slice
l = subs.slice.lower
u = subs.slice.upper
s = subs.slice.step
if col_t is None:
# If we can't assign a type to the collection, then we can't assign a
# type to its subscript.
return None
# String subscripting
elif col_t == str_t or col_t == unicode_t:
if is_index and infer_expr(i, env) == int_t:
# (sidx) assignment rule.
return col_t
elif is_slice and valid_int_slice(l, u, s, env):
# (sslc) assignment rule.
return col_t
else:
# No assignment rule found.
return None
# List subscripting
elif col_t.is_list():
if is_index and check.check_expr(i, int_t, env):
# (lidx) assignment rule.
return col_t.elt
elif is_slice and valid_int_slice(l, u, s, env):
# (lslc) assignment rule.
return col_t
else:
# No assignment rule found.
return None
# Tuple subscripting
elif col_t.is_tuple():
col_ts = col_t.elts
n = len(col_ts)
if is_index and node_is_int(i) and -n <= i.n < n:
# (tidx) assignment rule.
return col_ts[i.n]
elif is_slice:
rng = slice_range(l, u, s, len(col_ts))
if rng is not None:
# (tslc) assignment rule.
return PType.tuple([col_ts[i] for i in rng])
else:
# No assignment rule found.
return None
else:
# No assignment rule found.
return None
else:
# No assignment rule found.
return None
