literal array indices (#11424)

tests/array/tarray.nim

@@ -548,3 +548,12 @@ block t3899:
     x.a[i]
   const c = O(a: [1.0,2.0])
   echo c[2]
+
+block arrayLiterals:
+  type ABC = enum A, B, C
+  template Idx[IdxT, ElemT](arr: array[IdxT, ElemT]): untyped = IdxT
+  doAssert [A: 0, B: 1].Idx is range[A..B]
+  doAssert [A: 0, 1, 3].Idx is ABC
+  doAssert [1: 2][1] == 2
+  doAssert [-1'i8: 2][-1] == 2
+  doAssert [-1'i8: 2, 3, 4, 5].Idx is range[-1'i8..2'i8]

tests/array/tidx_lit_err1.nim

@@ -0,0 +1,6 @@
+discard """
+  errormsg: "size of array exceeds range of index type 'range 1..2(Color)' by 3 elements"
+  line: 6
+"""
+type Color = enum Red, Green, Blue
+let y = [Green: 0, 1, 2, 3, 4]

tests/array/tidx_lit_err2.nim

@@ -0,0 +1,5 @@
+discard """
+  errormsg: "expected ordinal value for array index, got '\"string\"'"
+  line: 5
+"""
+let x = ["string": 0, "index": 1]

tests/array/tidx_lit_err3.nim

@@ -0,0 +1,5 @@
+discard """
+  errormsg: "size of array exceeds range of index type 'range 2147483646..2147483647(int32)' by 1 elements"
+  line: 5
+"""
+echo [high(int32)-1: 1, 2, 3]