Casting to int inside loop yields numpy array indexing error

[Rik-de-Kort]

Float indexing for numpy arrays is deprecated, and as such it's not supported by numba.
When initiating a variable as a float, and casting it to an integer, and the using it to index a numpy array, this works fine. However, when we cast it to integer inside a loop, numba will throw an error saying float indexing is not supported.

MWE without error:

import numpy as np
from numba import njit

@njit()
def literally_can_(even):
    w = 0.0
    w = int(w)
    few = even[w]
    return 0

odd = np.array([0 for _ in range(1)], dtype="float64")
literally_can_(odd)

Adding a loop makes it throw an error:

@njit()
def literally_cant_(even):
    w = 0.0
    for _ in range(1):
        w = int(w)

    few = even[w]
    return 0

odd = np.array([0 for _ in range(1)], dtype="float64")
literally_cant_(odd)

Error produced

Traceback (most recent call last):
  File "C:/Users/user/Documents/ManagedDC/test.py", line 25, in <module>
    print(literally_cant_(odd))
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\dispatcher.py", line 330, in _compile_for_args
    raise e
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\dispatcher.py", line 307, in _compile_for_args
    return self.compile(tuple(argtypes))
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\dispatcher.py", line 579, in compile
    cres = self._compiler.compile(args, return_type)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\dispatcher.py", line 80, in compile
    flags=flags, locals=self.locals)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\compiler.py", line 766, in compile_extra
    return pipeline.compile_extra(func)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\compiler.py", line 362, in compile_extra
    return self._compile_bytecode()
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\compiler.py", line 725, in _compile_bytecode
    return self._compile_core()
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\compiler.py", line 712, in _compile_core
    res = pm.run(self.status)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\compiler.py", line 248, in run
    raise patched_exception
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\compiler.py", line 240, in run
    stage()
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\compiler.py", line 454, in stage_nopython_frontend
    self.locals)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\compiler.py", line 868, in type_inference_stage
    infer.propagate()
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typeinfer.py", line 844, in propagate
    raise errors[0]
numba.errors.TypingError: Failed at nopython (nopython frontend)
Internal error at <numba.typeinfer.IntrinsicCallConstraint object at 0x0000019D931991D0>:
--%<-----------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\errors.py", line 259, in new_error_context
    yield
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typeinfer.py", line 501, in __call__
    self.resolve(typeinfer, typeinfer.typevars, fnty=self.func)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typeinfer.py", line 441, in resolve
    sig = typeinfer.resolve_call(fnty, pos_args, kw_args, literals=literals)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typeinfer.py", line 1113, in resolve_call
    literals=literals)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typing\context.py", line 189, in resolve_function_type
    res = defn.apply(args, kws)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typing\templates.py", line 207, in apply
    sig = generic(args, kws)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typing\arraydecl.py", line 165, in generic
    out = get_array_index_type(ary, idx)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typing\arraydecl.py", line 71, in get_array_index_type
    % (ty, idx))
TypeError: unsupported array index type float64 in [float64]

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typeinfer.py", line 137, in propagate
    constraint(typeinfer)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typeinfer.py", line 501, in __call__
    self.resolve(typeinfer, typeinfer.typevars, fnty=self.func)
  File "C:\Users\user\Anaconda3\lib\contextlib.py", line 99, in __exit__
    self.gen.throw(type, value, traceback)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\errors.py", line 265, in new_error_context
    six.reraise(type(newerr), newerr, sys.exc_info()[2])
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\six.py", line 658, in reraise
    raise value.with_traceback(tb)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\errors.py", line 259, in new_error_context
    yield
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typeinfer.py", line 501, in __call__
    self.resolve(typeinfer, typeinfer.typevars, fnty=self.func)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typeinfer.py", line 441, in resolve
    sig = typeinfer.resolve_call(fnty, pos_args, kw_args, literals=literals)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typeinfer.py", line 1113, in resolve_call
    literals=literals)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typing\context.py", line 189, in resolve_function_type
    res = defn.apply(args, kws)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typing\templates.py", line 207, in apply
    sig = generic(args, kws)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typing\arraydecl.py", line 165, in generic
    out = get_array_index_type(ary, idx)
  File "C:\Users\user\Anaconda3\lib\site-packages\numba\typing\arraydecl.py", line 71, in get_array_index_type
    % (ty, idx))
numba.errors.InternalError: unsupported array index type float64 in [float64]
[1] During: typing of intrinsic-call at C:/Users/user/Documents/ManagedDC/test.py (11)
--%<-----------------------------------------------------------------

File "test.py", line 11

[sklam]

Related to #2719

[stuartarchibald]

This won't be fixed by SSA alone.