[instancer.solver] Add a special case

Lib/fontTools/varLib/instancer/solver.py

@@ -87,6 +87,10 @@ def _solve(tent, axisLimit):
             # we clamp +2.0 to the max F2Dot14 (~1.99994) for convenience
             upper = axisDef + (axisMax - axisDef) * MAX_F2DOT14
 
+        # Special-case if peak is at axisMax.
+        if axisMax == peak:
+            upper = peak
+
         loc = (max(axisDef, lower), peak, upper)
 
         # Don't add a dirac delta!

Tests/varLib/instancer/solver_test.py

@@ -181,6 +181,18 @@ class RebaseTentTest(object):
                     (1, (1, 1, 1)),
                 ]
             ),
+            pytest.param(
+                (.5, .5, .5), (.25, .35, .5),
+                [
+                    (1, (1, 1, 1)),
+                ]
+            ),
+            pytest.param(
+                (.5, .5, .55), (.25, .35, .5),
+                [
+                    (1, (1, 1, 1)),
+                ]
+            ),
         ],
     )
     def test_rebaseTent(self, tent, axisRange, expected):