Improve boundary handling (#6684)

* correct parenthesis

* add contingent case

* add news bullet

Author: teunbrand

NEWS.md

@@ -2,6 +2,7 @@
 
 ### Bug fixes
 
+* Fixed bug where `stat_bin(boundary)` was ignored (#6682).
 * `geom_text()` and `geom_label()` accept expressions as the `label` aesthetic 
   (@teunbrand, #6638)
 * Fixed regression where `draw_key_rect()` stopped using `fill` colours 

R/bin.R

@@ -105,7 +105,12 @@ bin_breaks_bins <- function(x_range, bins = 30, center = NULL,
   } else {
     width <- (x_range[2] - x_range[1]) / (bins - 1)
     if (is.null(center)) {
-      boundary <- boundary %||% x_range[1] - width / 2
+      boundary <- boundary %||% (x_range[1] - width / 2)
+    }
+    # If `x_range` coincides with boundary we should
+    # use exact `bins` instead of `bins - 1` to prevent misalignments.
+    if (!is.null(boundary) && any(x_range %% width == boundary %% width)) {
+      width <- (x_range[2] - x_range[1]) / bins
     }
   }