support for inferring static[T] concept params

tests/concepts/tmatrixconcept.nim

@@ -0,0 +1,67 @@
+discard """
+output: "0\n0"
+msg: '''
+R=3 C=3 TE=9 FF=14 FC=20 T=int
+'''
+"""
+
+import typetraits
+
+template ok(x) = assert x
+template no(x) = assert(not x)
+
+const C = 10
+
+type
+  Matrix[Rows, Cols, TotalElements, FromFoo, FromConst: static[int]; T] = concept m, var mvar, type M
+    M.M == Rows
+    Cols == M.N
+    M.T is T
+
+    m[int, int] is T
+    mvar[int, int] = T
+
+    FromConst == C * 2
+
+    # more complicated static param inference cases
+    m.data is array[TotalElements, T]
+    M.foo(array[0..FromFoo, type m[int, 10]])
+
+  MyMatrix[M, K: static[int]; T] = object
+    data: array[M*K, T]
+
+# adaptor for the concept's non-matching expectations
+template N(M: type MyMatrix): expr = M.K
+
+proc `[]`(m: MyMatrix; r, c: int): m.T =
+  m.data[r * m.K + c]
+
+proc `[]=`(m: var MyMatrix; r, c: int, v: m.T) =
+  m.data[r * m.K + c] = v
+
+proc foo(x: MyMatrix, arr: array[15, x.T]) = discard
+
+proc matrixProc[R, C, TE, FF, FC, T](m: Matrix[R, C, TE, FF, FC, T]): T =
+  static:
+    echo "R=", R, " C=", C, " TE=", TE, " FF=", FF, " FC=", FC, " T=", T.name
+  
+  m[0, 0]
+
+proc myMatrixProc(x: MyMatrix): MyMatrix.T = matrixProc(x)
+
+var x: MyMatrix[3, 3, int]
+
+static:
+  # ok x is Matrix
+  ok x is Matrix[3, 3, 9, 14, 20, int]
+
+  no x is Matrix[3, 3, 8, 15, 20, int]
+  no x is Matrix[3, 3, 9, 10, 20, int]
+  no x is Matrix[3, 3, 9, 15, 21, int]
+  no x is Matrix[3, 3, 9, 15, 20, float]
+  no x is Matrix[4, 3, 9, 15, 20, int]
+  no x is Matrix[3, 4, 9, 15, 20, int]
+
+echo x.myMatrixProc
+echo x.matrixProc
+