fix: reject non-positive bins

CHANGELOG.md

@@ -12,6 +12,7 @@
 - feat: `labs()` fields default to `auto`; pass `none` to suppress an axis or legend title and reclaim the space it reserved. (#12)
 - feat: `element-blank()` on a text surface (axis, plot, or legend title) collapses the space the text would reserve. (#12)
 - feat: `width`/`height` accept `auto` to fill the available space of a bounded container. (#10)
+- fix: binning geoms reject a non-positive `bins` with a clear error instead of dividing by zero. (#38)
 - fix: contour stats skip incomplete cells when the `(x, y, z)` grid is sparse instead of panicking. (#37)
 - fix: `scale-*-manual()` with an empty `values` array reports a clear error instead of an opaque divide-by-zero. (#36)
 - fix: number formatters carry a fraction that rounds up to a whole unit (e.g., `0.9999995` no longer renders as `0.1`), and `format-scientific` keeps its mantissa in `[1, 10)`. (#35)

src/utils/bin.typ

@@ -21,6 +21,10 @@
   let n-bins = if binwidth != none and binwidth > 0 {
     calc.max(1, int(calc.ceil((hi - lo) / binwidth)))
   } else {
+    assert(
+      bins != none and bins > 0,
+      message: "bins must be a positive integer; got " + repr(bins),
+    )
     bins
   }
   (n-bins: n-bins, width: (hi - lo) / n-bins)