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from numba.core import errors, ir
from numba.core.rewrites import register_rewrite, Rewrite
@register_rewrite('before-inference')
class RewriteConstRaises(Rewrite):
"""
Rewrite IR statements of the kind `raise(value)`
where `value` is the result of instantiating an exception with
constant arguments
into `static_raise(exception_type, constant args)`.
This allows lowering in nopython mode, where one can't instantiate
exception instances from runtime data.
"""
def _is_exception_type(self, const):
return isinstance(const, type) and issubclass(const, Exception)
def _break_constant(self, const, loc):
"""
Break down constant exception.
"""
if isinstance(const, tuple): # it's a tuple(exception class, args)
if not self._is_exception_type(const[0]):
msg = "Encountered unsupported exception constant %r"
raise errors.UnsupportedError(msg % (const[0],), loc)
return const[0], tuple(const[1])
elif self._is_exception_type(const):
return const, None
else:
if isinstance(const, str):
msg = ("Directly raising a string constant as an exception is "
"not supported.")
else:
msg = "Encountered unsupported constant type used for exception"
raise errors.UnsupportedError(msg, loc)
def match(self, func_ir, block, typemap, calltypes):
self.raises = raises = {}
self.tryraises = tryraises = {}
self.block = block
# Detect all raise statements and find which ones can be
# rewritten
for inst in block.find_insts((ir.Raise, ir.TryRaise)):
if inst.exception is None:
# re-reraise
exc_type, exc_args = None, None
else:
# raise <something> => find the definition site for <something>
const = func_ir.infer_constant(inst.exception)
loc = inst.exception.loc
exc_type, exc_args = self._break_constant(const, loc)
if isinstance(inst, ir.Raise):
raises[inst] = exc_type, exc_args
elif isinstance(inst, ir.TryRaise):
tryraises[inst] = exc_type, exc_args
else:
raise ValueError('unexpected: {}'.format(type(inst)))
return (len(raises) + len(tryraises)) > 0
def apply(self):
"""
Rewrite all matching setitems as static_setitems.
"""
new_block = self.block.copy()
new_block.clear()
for inst in self.block.body:
if inst in self.raises:
exc_type, exc_args = self.raises[inst]
new_inst = ir.StaticRaise(exc_type, exc_args, inst.loc)
new_block.append(new_inst)
elif inst in self.tryraises:
exc_type, exc_args = self.tryraises[inst]
new_inst = ir.StaticTryRaise(exc_type, exc_args, inst.loc)
new_block.append(new_inst)
else:
new_block.append(inst)
return new_block
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