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Merged
merged 1 commit into from
Aug 15, 2025
Merged

py/parse: Remove explicit checks for invalid folding operations. #17883

merged 1 commit into from
Aug 15, 2025

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dpgeorge
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Summary

They are instead checked by binary_op_maybe(), which catches exceptions for invalid int/float operations.

This is a follow-up to 69ead7d / #16666.

Testing

Tested with the unix port, with floats disabled.

The following do not raise exceptions (as expected) because the folding is not done:

compile("1/2","file","eval")
compile("1**-2","file","eval")
compile("1@2","file","eval")

Then I validated that the bytecode has the explicit operator calls:

$ micropython -v -v -v
...
>>> (1+2)@4
File <stdin>, code block '<module>' (descriptor: 7f0d487eed80, bytecode @7f0d487eeca0 13 bytes)
Raw bytecode (code_info_size=3, bytecode_size=10):
 10 02 01 11 02 83 84 f5 34 01 59 51 63
arg names:
(N_STATE 3)
(N_EXC_STACK 0)
  bc=0 line=1
00 LOAD_NAME __repl_print__
02 LOAD_CONST_SMALL_INT 3
03 LOAD_CONST_SMALL_INT 4
04 BINARY_OP 30 __matmul__
05 CALL_FUNCTION n=1 nkw=0
07 POP_TOP
08 LOAD_CONST_NONE
09 RETURN_VALUE
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported types for __matmul__: 'int', 'int'

You can see that the (1+2) is folded but not the @ operator, which is then evaluated at runtime. And also:

>>> 1**(-2)
File <stdin>, code block '<module>' (descriptor: 7f0d487eef00, bytecode @7f0d487eee80 13 bytes)
Raw bytecode (code_info_size=3, bytecode_size=10):
 10 02 01 11 02 81 7e f9 34 01 59 51 63
arg names:
(N_STATE 3)
(N_EXC_STACK 0)
  bc=0 line=1
00 LOAD_NAME __repl_print__
02 LOAD_CONST_SMALL_INT 1
03 LOAD_CONST_SMALL_INT -2
04 BINARY_OP 34 __pow__
05 CALL_FUNCTION n=1 nkw=0
07 POP_TOP
08 LOAD_CONST_NONE
09 RETURN_VALUE
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: negative power with no float support
>>> 1/2
File <stdin>, code block '<module>' (descriptor: 7f0d487ef300, bytecode @7f0d487ef120 13 bytes)
Raw bytecode (code_info_size=3, bytecode_size=10):
 10 02 01 11 02 81 82 f7 34 01 59 51 63
arg names:
(N_STATE 3)
(N_EXC_STACK 0)
  bc=0 line=1
00 LOAD_NAME __repl_print__
02 LOAD_CONST_SMALL_INT 1
03 LOAD_CONST_SMALL_INT 2
04 BINARY_OP 32 __truediv__
05 CALL_FUNCTION n=1 nkw=0
07 POP_TOP
08 LOAD_CONST_NONE
09 RETURN_VALUE
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported types for __truediv__: 'int', 'int'

Trade-offs and Alternatives

This means the test is delegated to binary_op_maybe(), making the check for invalid folding operations a little slower. But it saves code size and it's rare that the user does invalid binary operations on literal numbers.

@dpgeorge dpgeorge added the py-core Relates to py/ directory in source label Aug 11, 2025
@dpgeorge
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@yoctopuce FYI. I think this is a safe change to make.

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Code size report:

   bare-arm:    +0 +0.000% 
minimal x86:    +0 +0.000% 
   unix x64:   -16 -0.002% standard
      stm32:    -8 -0.002% PYBV10
     mimxrt:    -8 -0.002% TEENSY40
        rp2:    -8 -0.001% RPI_PICO_W
       samd:    -8 -0.003% ADAFRUIT_ITSYBITSY_M4_EXPRESS
  qemu rv32:   -14 -0.003% VIRT_RV32

@yoctopuce
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Yes, I agree, this looks completely safe.

@dpgeorge
py/parse: Remove explicit checks for invalid folding operations.
3efbd72 
They are instead checked by `binary_op_maybe()`, which catches exceptions
for invalid int/float operations.

This is a follow-up to 69ead7d

Signed-off-by: Damien George <damien@micropython.org>
@dpgeorge dpgeorge force-pushed the py-parse-simplify-invalid-folding-checks branch from 000d1d8 to 3efbd72 Compare August 15, 2025 01:38
@dpgeorge dpgeorge merged commit 3efbd72 into micropython:master Aug 15, 2025
68 of 69 checks passed
@dpgeorge dpgeorge deleted the py-parse-simplify-invalid-folding-checks branch August 15, 2025 01:44
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codecov bot commented Aug 15, 2025

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.38%. Comparing base (141f7d0) to head (3efbd72).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files 
@@            Coverage Diff             @@
##           master   #17883      +/-   ##
==========================================
- Coverage   98.38%   98.38%   -0.01%     
==========================================
  Files         171      171              
  Lines       22298    22297       -1     
==========================================
- Hits        21939    21938       -1     
  Misses        359      359

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@dpgeorge @yoctopuce