8000 Add --warn-no-return, and major binder refactoring by rwbarton · Pull Request #1748 · python/mypy · GitHub
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Add --warn-no-return, and major binder refactoring #1748

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Merged
merged 13 commits into from
Oct 18, 2016
Merged

Add --warn-no-return, and major binder refactoring #1748

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9c70f3d
Replace the binder's breaking_out by an 'unreachable' property of Frame
rwbarton Jun 26, 2016
673b205
Minor type cleanup in the binder and explanation of Key
rwbarton Jun 28, 2016
73815df
Learn that loop condition is False on exit from while loop
rwbarton Jun 28, 2016
0a9c3c5
Use bool() in tests when we want an unspecified bool in a conditional
rwbarton Jun 28, 2016
d064ce5
Handle 'while True', 'assert False'
rwbarton Jun 28, 2016
cf50f43
Reduce duplication with find_isinstance_check and binder.push
rwbarton Jun 28, 2016
4388a81
Process try statements in top-to-bottom order
rwbarton Jun 29, 2016
5b51181
Fix return type of binder.unreachable
rwbarton Jul 1, 2016
1f6a43b
Add warn-no-return flag to give a note on missing return statements
ecprice Jun 22, 2016
a6c2119
Skip docstring when determining whether function body is trivial
rwbarton Jul 1, 2016
6fbddba
Remove None return values from check_return_stmt
rwbarton Jul 1, 2016
0af2236
Explain why two try frames are needed for a finally clause; add a test
rwbarton Jul 1, 2016
f20db90
Decouple checker and binder by adding more options to frame_context
rwbarton Jul 1, 2016
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Process try statements in top-to-bottom order 
Fixes #1289 (again).
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@rwbarton
rwbarton committed Oct 13, 2016
commit 4388a8145eea27692a0884c7716b919aafe85f69
79 changes: 43 additions & 36 deletions mypy/checker.py
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Expand Up @@ -1643,44 +1643,51 @@ def visit_try_stmt(self, s: TryStmt) -> Type:
def visit_try_without_finally(self, s: TryStmt) -> None:
"""Type check a try statement, ignoring the finally block.

Otherwise, it will place the results possible frames of
that don't break out into self.binder.frames[-2].
On entry, the top frame should receive all flow that exits the
try block abnormally (i.e., such that the else block does not
execute), and its parent should receive all flow that exits
the try block normally.
"""
# This frame records the possible states that exceptions can leave variables in
# during the try: block
with self.binder.frame_context(can_skip=False, fall_through=0):
with self.binder.frame_context(can_skip=False, fall_through=3):
self.binder.try_frames.add(len(self.binder.frames) - 2)
self.binder.allow_jump(-1)
self.accept(s.body)
self.binder.try_frames.remove(len(self.binder.frames) - 2)
if s.else_body:
self.accept(s.else_body)
for i in range(len(s.handlers)):
with self.binder.frame_context(can_skip=True, fall_through=3):
if s.types[i]:
t = self.visit_except_handler_test(s.types[i])
# This frame will run the else block if the try fell through.
# In that case, control flow continues to the parent of what
# was the top frame on entry.
with self.binder.frame_context(can_skip=False, fall_through=2):
# This frame receives exit via exception, and runs exception handlers
with self.binder.frame_context(can_skip=False, fall_through=2):
# Finally, the body of the try statement
with self.binder.frame_context(can_skip=False, fall_through=2):
self.binder.try_frames.add(len(self.binder.frames) - 2)
self.binder.allow_jump(-1)
self.accept(s.body)
self.binder.try_frames.remove(len(self.binder.frames) - 2)
for i in range(len(s.handlers)):
with self.binder.frame_context(can_skip=True, fall_through=4):
if s.types[i]:
t = self.visit_except_handler_test(s.types[i])
if s.vars[i]:
# To support local variables, we make this a definition line,
# causing assignment to set the variable's type.
s.vars[i].is_def = True
self.check_assignment(s.vars[i], self.temp_node(t, s.vars[i]))
self.accept(s.handlers[i])
if s.vars[i]:
# To support local variables, we make this a definition line,
# causing assignment to set the variable's type.
s.vars[i].is_def = True
self.check_assignment(s.vars[i], self.temp_node(t, s.vars[i]))
self.accept(s.handlers[i])
if s.vars[i]:
# Exception variables are deleted in python 3 but not python 2.
8000 # But, since it's bad form in python 2 and the type checking
# wouldn't work very well, we delete it anyway.

# Unfortunately, this doesn't let us detect usage before the
# try/except block.
if self.options.python_version[0] >= 3:
source = s.vars[i].name
else:
source = ('(exception variable "{}", which we do not accept outside'
'except: blocks even in python 2)'.format(s.vars[i].name))
var = cast(Var, s.vars[i].node)
var.type = DeletedType(source=source)
self.binder.cleanse(s.vars[i])
# Exception variables are deleted in python 3 but not python 2.
# But, since it's bad form in python 2 and the type checking
# wouldn't work very well, we delete it anyway.

# Unfortunately, this doesn't let us detect usage before the
# try/except block.
if self.options.python_version[0] >= 3:
source = s.vars[i].name
else:
source = ('(exception variable "{}", which we do not '
'accept outside except: blocks even in '
'python 2)'.format(s.vars[i].name))
var = cast(Var, s.vars[i].node)
var.type = DeletedType(source=source)
self.binder.cleanse(s.vars[i])
if s.else_body:
self.accept(s.else_body)

def visit_except_handler_test(self, n: Expression) -> Type:
"""Type check an exception handler test clause."""
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3 changes: 0 additions & 3 deletions test-data/unit/check-optional.test
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Expand Up @@ -368,9 +368,6 @@ def lookup_field(name, obj):
attr = f()
else:
attr = None
[out]
main: note: In function "lookup_field":
main:10: error: Need type annotation for variable

[case testTernaryWithNone]
reveal_type(None if bool() else 0) # E: Revealed type is 'Union[builtins.int, builtins.None]'
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2 changes: 1 addition & 1 deletion test-data/unit/check-statements.test
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Expand Up @@ -530,7 +530,7 @@ else:
object(None) # E: Too many arguments for "object"
[builtins fixtures/exception.pyi]

[case testRedefinedFunctionInTryWithElse-skip]
[case testRedefinedFunctionInTryWithElse]
def f() -> None: pass
try:
pass
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0