Hybrid version of sum(na.rm = FALSE) exits early when there are mis…

…sing values. closes #3288.
tidyverse · May 29, 2018 · 565bd6e · 565bd6e
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commit 565bd6e
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diff --git a/NEWS.md b/NEWS.md
@@ -17,7 +17,8 @@
 - new method `group_data()` (#3489).
 - joins no longer make lazy grouped data (#3566). 
 - new `nest_join()` function. `nest_join()` creates a list column of the matching rows. `nest_join()` + `tidyr::unnest()` is equivalent to `inner_join`  (#3570). 
-- `last_col()` is re-exported from tidyselect (#3584)
+- `last_col()` is re-exported from tidyselect (#3584). 
+- hybrid version of `sum(na.rm = FALSE)` exits early when there are missing values (#3288). 
 
 # dplyr 0.7.5.9001
 

diff --git a/inst/include/dplyr/Result/Sum.h b/inst/include/dplyr/Result/Sum.h
@@ -46,14 +46,14 @@ struct Sum<REALSXP, NA_RM, Index> {
     for (int i = 0; i < n; i++) {
       double value = ptr[indices[i]];
 
-      // !NA_RM: we don't test for NA here because += NA will give NA
-      // this is faster in the most common case where there are no NA
-      // if there are NA, we could return quicker as in the version for
-      // INTSXP, but we would penalize the most common case
       if (NA_RM && Rcpp::traits::is_na<REALSXP>(value)) {
         continue;
       }
 
+      if (!NA_RM && Rcpp::traits::is_na<REALSXP>(value)) {
+        return NA_REAL;
+      }
+
       res += value;
     }