[galafis]

LinearConstraint.combine() documents its argument as an iterable of constraints, but indexes it before iterating over it repeatedly. Passing a list iterator or generator raises TypeError instead of combining the constraints. An empty iterator also bypasses the existing empty-input check.

Materialize the iterable once before validation. This preserves the existing coefficient/constant stacking and variable-name checks while accepting single-pass inputs. The regression test checks list iterators and generator expressions against explicit expected coefficient and constant matrices, and checks the existing ValueError messages for empty and incompatible inputs.

Validation: the new regression fails before the fix while the existing combine test passes (1 failed, 1 passed). After the fix the complete suite passes (163 passed). Project-pinned Ruff 0.17.1 format --check and git diff --check pass. Tested with Python 3.12.14, NumPy 2.5.4, pandas 2.3.3, SciPy 1.18.1 and pytest 9.1.1. No statistical computation is changed.