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Prevent crash on retrieving TypeVar from class #2544

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Merged
merged 5 commits into from
Dec 14, 2016
Merged

Prevent crash on retrieving TypeVar from class #2544

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7a86ce0
Prevent crash on retrieving TypeVars from classes
TRManderson Dec 9, 2016
eb300a5
Add test for accessing TypeVar class members
TRManderson Dec 9, 2016
586a5e5
Merge remote-tracking branch 'mypy/master' into aliasing-crash
Dec 11, 2016
ae0fdd9
Add trailing newline
Dec 13, 2016
ed1760c
TypeVar class members should have the type TypeVarType
TRManderson Dec 13, 2016
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5 changes: 4 additions & 1 deletion mypy/checkmember.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@
Overloaded, TypeVarType, UnionType, PartialType,
DeletedType, NoneTyp, TypeType, function_type
)
from mypy.nodes import TypeInfo, FuncBase, Var, FuncDef, SymbolNode, Context, MypyFile
from mypy.nodes import TypeInfo, FuncBase, Var, FuncDef, SymbolNode, Context, MypyFile, TypeVarExpr
from mypy.nodes import ARG_POS, ARG_STAR, ARG_STAR2
from mypy.nodes import Decorator, OverloadedFuncDef
from mypy.messages import MessageBuilder
Expand Down Expand Up @@ -378,6 +378,9 @@ def analyze_class_attribute_access(itype: Instance,
not_ready_callback(name, context)
return AnyType()

if isinstance(node.node, TypeVarExpr):
return node.node.upper_bound
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If we don't support it, this should also report an error message. (In error recovery mode, returning the upper bound sounds fine.)

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As far as I know (not very far) we theoretically do support accessing TypeVars that are members of a class, we just don't support aliasing them. I'll try and come up with a valid example (or counterexample) after I finish work.

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Also, WRT returning the upper bound, I feel like it's wrong in this context - the type of accessing a class member TypeVar should be TypeVar(I'm not 100% on how that's internally represented), and aliasing should still fail.


if isinstance(node.node, TypeInfo):
return type_object_type(node.node, builtin_type)

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8 changes: 8 additions & 0 deletions test-data/unit/check-typevar-values.test
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Expand Up @@ -489,3 +489,11 @@ def outer(x: T) -> T:
return inner1('a') # E: Argument 1 to "inner1" has incompatible type "str"; expected "int"
return inner1(x)
[out]

[case testClassMemberTypeVarInFunctionBody]
from typing import TypeVar
class C:
T = TypeVar('T', int)
def f(self, x: T) -> T:
A = C.T
return x
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Can you add the missing newline here?

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Fixed