fixes #2250

tests/ccgbugs/tuple_canon.nim

@@ -0,0 +1,80 @@
+# bug #2250
+
+import
+    math, strutils
+
+type
+    Meters = float
+    Point2[T] = tuple[x, y: T]
+
+    HexState* = enum
+        hsOn, hsOff
+
+    Index = uint16
+
+    HexGrid* = object
+        w, h: int                       ## Width and height of the hex grid.
+        radius: Meters                  ## Radius of circle that circumscribes a hexagon.
+        grid: seq[HexState]             ## Information on what hexes are drawn.
+
+    HexVtxIndex = enum
+        hiA, hiB, hiC, hiD, hiE, hiF
+
+    HexCoord* = Point2[int]
+
+const
+    HexDY = sqrt(1.0 - (0.5 * 0.5))     # dy from center to midpoint of 1-2
+    HexDX = sqrt(1.0 - (HexDY * HexDY)) # dx from center to midpoint of 1-5 (0.5)
+
+
+let
+    hexOffsets : array[HexVtxIndex, Point2[float]] = [
+                  (-1.0, 0.0),
+                  (-HexDX, -HexDY),
+                  (HexDX, -HexDY),
+                  (1.0, 0.0),
+                  (HexDX, HexDY),
+                  (-HexDX, HexDY)]
+
+    evenSharingOffsets : array[HexVtxIndex, tuple[hc: HexCoord; idx: HexVtxIndex]] = [
+            ((0,0), hiA),
+            ((0,0), hiB),
+            ((1,-1), hiA),
+            ((1,0), hiB),
+            ((1,0), hiA),
+            ((0,1), hiB)]
+
+    oddSharingOffsets : array[HexVtxIndex, tuple[hc: HexCoord; idx: HexVtxIndex]] = [
+            ((0,0), hiA),
+            ((0,0), hiB),
+            ((1,0), hiA),
+            ((1,1), hiB),
+            ((1,1), hiA),
+            ((0,1), hiB)]
+
+template odd*(i: int) : expr =
+    (i and 1) != 0
+
+proc vidx(hg: HexGrid; col, row: int; i: HexVtxIndex) : Index =
+    #NOTE: this variation compiles
+    #var offset : type(evenSharingOffsets[i])
+    #
+    #if odd(col):
+    #    offset = oddSharingOffsets[i]
+    #else:
+    #    offset = evenSharingOffsets[i]
+
+    let
+        #NOTE: this line generates the bad code
+        offset = (if odd(col): oddSharingOffsets[i] else: evenSharingOffsets[i])
+        x = col + 1 + offset.hc.x
+        y = row + 1 + offset.hc.y
+
+    result = Index(x*2 + y * (hg.w + 2)*2 + int(offset.idx))
+
+proc go() =
+    var hg : HexGrid
+
+    echo "vidx ", $vidx(hg, 1, 2, hiC)
+
+go()