fix #1013

tests/matrix/issue1013.nim

@@ -0,0 +1,23 @@
+import typetraits
+
+template reject(e: expr) =
+  static: assert(not compiles(e))
+
+type
+  TMatrix[T; M, N: static[int]] = array[M*N, T]
+
+proc `*`[T; R, N, C](a: TMatrix[T, R, N], b: TMatrix[T, N, C]): TMatrix[T, R, C] =
+  discard
+
+var m1: TMatrix[int, 6, 4]
+var m2: TMatrix[int, 4, 3]
+var m3: TMatrix[int, 3, 3]
+
+var m4 = m1*m2
+static: assert m4.M == 6 and m4.N == 3
+
+reject m1 * m3 # not compatible
+
+var m5 = m2 * m3
+static: assert high(m5) == 11 # 4*3 - 1
+