Compile first source file, not last

Some source files may include other files of the same type which can get
injected at the end.

2 files changed, 7 insertions, 7 deletions

diff --git a/build2/algorithm b/build2/algorithm
index 9f43475..db2ccca 100644
--- a/build2/algorithm
+++ b/build2/algorithm
@@ -190,12 +190,12 @@ namespace build2
   bool
   execute_prerequisites (action, target&, const timestamp&);
 
-  // Another version of the above that does two extra things for the
-  // caller: it determines whether the action needs to be executed on
-  // the target based on the passed timestamp and, if so, finds a
-  // prerequisite of the specified type (e.g., a source file). If
-  // there are multiple prerequisites of this type, then the last
-  // is returned.
+  // Another version of the above that does two extra things for the caller:
+  // it determines whether the action needs to be executed on the target based
+  // on the passed timestamp and, if so, finds a prerequisite of the specified
+  // type (e.g., a source file). If there are multiple prerequisites of this
+  // type, then the first is returned (this can become important if additional
+  // prerequisites of the same type may get injected).
   //
   template <typename T>
   T*
diff --git a/build2/algorithm.cxx b/build2/algorithm.cxx
index 6b28232..8dc5621 100644
--- a/build2/algorithm.cxx
+++ b/build2/algorithm.cxx
@@ -494,7 +494,7 @@ namespace build2
         }
       }
 
-      if (pt->is_a (tt))
+      if (r == nullptr && pt->is_a (tt))
         r = pt;
     }