api: fix evaluation with different time dims

devito/symbolics/manipulation.py

@@ -16,7 +16,9 @@
 from devito.symbolics.unevaluation import Mul as UnevalMul
 from devito.symbolics.unevaluation import Pow as UnevalPow
 from devito.symbolics.unevaluation import UnevaluableMixin
-from devito.tools import as_list, as_tuple, flatten, split, transitive_closure
+from devito.tools import (
+    EnrichedTuple, as_list, as_tuple, flatten, split, transitive_closure
+)
 from devito.types.array import ComponentAccess
 from devito.types.basic import Basic, Indexed
 from devito.types.equation import Eq
@@ -130,6 +132,12 @@ def _(iterable, rule):
     return iterable.__class__(ret), changed
 
 
+@_uxreplace_dispatch.register(EnrichedTuple)
+def _(iterable, rule):
+    retval, changed = _uxreplace_dispatch(tuple(iterable), rule)
+    return iterable.__class__(*retval, getters=iterable.getters), changed
+
+
 @_uxreplace_dispatch.register(dict)
 def _(mapper, rule):
     ret = {}

devito/types/basic.py

@@ -971,7 +971,7 @@ def origin(self):
     @property
     def dimensions(self):
         """Tuple of Dimensions representing the object indices."""
-        return self._dimensions
+        return DimensionTuple(*self._dimensions, getters=self._dimensions)
 
     @cached_property
     def space_dimensions(self):

devito/types/dense.py

@@ -1128,7 +1128,8 @@ def _eval_at(self, func):
         for d in self.dimensions:
             try:
                 if self.indices_ref[d] is not func.indices_ref[d]:
-                    mapper[self.indices_ref[d]] = func.indices_ref[d]
+                    f_idx = func.indices_ref[d]._subs(func.dimensions[d], d)
+                    mapper[self.indices_ref[d]] = f_idx
             except KeyError:
                 pass
 

tests/test_staggered_utils.py

@@ -187,3 +187,16 @@ def test_staggered_rebuild(stagg):
             assert f2.indices[nd] == nd + nd.spacing / 2
         else:
             assert f2.indices[nd] == nd
+
+
+def test_eval_at_different_dim():
+    grid = Grid(shape=(31, 17, 25))
+    nt = 5
+    x, _, _ = grid.dimensions
+
+    v = TimeFunction(name="v", grid=grid, staggered=x)
+    tau = TimeFunction(name="tau", grid=grid, save=nt)
+
+    eq = Eq(tau.forward, v).evaluate
+
+    assert grid.time_dim not in eq.rhs.free_symbols