bug fix in expresion, Union: propagate the disjointness property

To avoid too many intermediate results, we compute the union of
a list in a divide and conquer fashion. Of course, for a disjoint
union, the recursive calls on the lists of half the length have to
be disjoint as well, i.e., the template parameter kDisjoint has to
be passed on. Fix this.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/buildtool/build_engine/expression/evaluator.cpp b/src/buildtool/build_engine/expression/evaluator.cpp
index 8945fe0e..34e0873b 100644
--- a/src/buildtool/build_engine/expression/evaluator.cpp
+++ b/src/buildtool/build_engine/expression/evaluator.cpp
@@ -344,8 +344,8 @@ auto Union(Expression::list_t const& dicts, size_t from, size_t to)
         return entry;
     }
     size_t mid = from + (to - from) / 2;
-    auto left = Union(dicts, from, mid);
-    auto right = Union(dicts, mid, to);
+    auto left = Union<kDisjoint>(dicts, from, mid);
+    auto right = Union<kDisjoint>(dicts, mid, to);
     if (left->Map().empty()) {
         return right;
     }