Fix the type check the previous commit did not run

CI runs bare `mypy`, over all 57 files. I ran `mypy src/oosim/`, which
skips tests and examples, and pushed on the strength of it.

Two things it would have caught. `row` had already been inferred as
list[str] earlier in the same function, so reusing the name for a list of
EVM floats made the subtraction a string operation. And six `type: ignore`
comments were unnecessary, which mypy reports as errors under its own
strictness settings.

No behaviour change: the example prints the same table.

Author: ehsun-sh

examples/wdm_nonlinear.py

@@ -274,7 +274,7 @@ def main() -> None:
     print("     " + "-" * 60)
     for launch_dbm in (-3.0, 0.0, 3.0):
         for dispersion in (0.0, 17.0):
-            row = []
+            evms = []
             for coupled in (False, True):
                 graph, ports = build(
                     channels=CHANNELS,
@@ -283,10 +283,10 @@ def main() -> None:
                     coupled=coupled,
                     mixing=coupled,
                 )
-                row.append(graph.run()[ports["vsa"]].evm * 100.0)
+                evms.append(graph.run()[ports["vsa"]].evm * 100.0)
             print(
                 f"     {launch_dbm:5.0f}dBm  {dispersion:6.0f}ps/nm/km  "
-                f"{row[0]:10.2f} %  {row[1]:7.2f} %  {row[1] - row[0]:+8.2f} %"
+                f"{evms[0]:10.2f} %  {evms[1]:7.2f} %  {evms[1] - evms[0]:+8.2f} %"
             )
     print("     the independent column is what this simulator reported before today.")
     print("     at zero dispersion the neighbours never slide past, so the penalty is")

tests/test_wdm_nonlinearity.py

@@ -279,7 +279,7 @@ def test_step_bounds_must_be_positive(bad: dict[str, float]) -> None:
             gamma=GAMMA,
             alpha=ALPHA,
             distance=SPAN,
-            **bad,  # type: ignore[arg-type]
+            **bad,
         )
 
 
@@ -355,8 +355,8 @@ def test_non_degenerate_products_are_six_db_stronger() -> None:
         "distance": SPAN,
         "phase_mismatch": 0.0,
     }
-    degenerate = fwm_product_power(POWER, POWER, POWER, degenerate=True, **common)  # type: ignore[arg-type]
-    mixed = fwm_product_power(POWER, POWER, POWER, degenerate=False, **common)  # type: ignore[arg-type]
+    degenerate = fwm_product_power(POWER, POWER, POWER, degenerate=True, **common)
+    mixed = fwm_product_power(POWER, POWER, POWER, degenerate=False, **common)
     assert 10.0 * math.log10(mixed / degenerate) == pytest.approx(6.0206, rel=1e-6)
 
 
@@ -554,6 +554,6 @@ def test_a_linear_span_is_untouched_by_either_effect() -> None:
     ctx, signal = comb(4)
     fiber = Fiber(length=80.0, attenuation=0.2, dispersion=17.0, nonlinearity=0.0)
     result = fiber.run(ctx, {"in": signal})
-    assert result["diagnostics"].mixing_products == 0  # type: ignore[attr-defined]
-    assert result["diagnostics"].steps == 0  # type: ignore[attr-defined]
-    assert len(result["out"].bands) == 4  # type: ignore[attr-defined]
+    assert result["diagnostics"].mixing_products == 0
+    assert result["diagnostics"].steps == 0
+    assert len(result["out"].bands) == 4