implements const set union (#1194)

This is required to compile `src/lib/nifreader.nim` with Nimony.

Author: demotomohiro

src/nimony/expreval.nim

@@ -225,6 +225,74 @@ template evalBinOp(c: var EvalContext; n: var Cursor; opr: untyped) {.dirty.} =
   else:
     evalOrdBinOp(c, n, opr)
 
+proc intToToken(result: var TokenBuf; x: int; typ: Cursor) =
+  case typ.typeKind
+  of IT:
+    result.addIntLit x
+  of UT:
+    result.addUIntLit uint x
+  of CT:
+    result.add charToken(char x, NoLineInfo)
+  else:
+    assert false, "Got unexpected type: " & toString(typ)
+
+proc bitSetToTokens(result: var TokenBuf; x: seq[uint8]; elementTyp: Cursor; info: PackedLineInfo) =
+  result.addParLe SetConstrX, info
+  result.buildTree TagId(SetT), NoLineInfo:
+    result.addSubtree elementTyp
+
+  var start = -1
+  for i in 0 ..< x.len:
+    for j in 0..7:
+      let val = i * 8 + j
+      if (x[i] and (1'u8 shl j)) == 0:
+        if start != -1:
+          if val - start < 5:
+            for k in start ..< val:
+              result.intToToken k, elementTyp
+          else:
+            result.addParLe RangeU
+            result.intToToken start, elementTyp
+            result.intToToken (val - 1), elementTyp
+            result.addParRi
+          start = -1
+      else:
+        if start == -1:
+          start = val
+
+  result.addParRi
+
+proc evalBitSet*(n, typ: Cursor): seq[uint8]
+
+proc evalPlusSet(c: var EvalContext; n: var Cursor): Cursor =
+  let info = n.info
+  inc n # tag
+  assert n.typeKind == SetT
+  var elementTyp = n
+  inc elementTyp
+  skip n # skip type
+  var a = eval(c, n)
+  var b = eval(c, n)
+  skipParRi n # skip last parRi
+  assert a.exprKind == SetConstrX, "got " & toString(a)
+  assert b.exprKind == SetConstrX, "got " & toString(b)
+  var typeA = a
+  inc typeA
+  var typeB = b
+  inc typeB
+  assert sameTrees(typeA, typeB)  # must be the same type
+  let setA = evalBitSet(a, typeA)
+  let setB = evalBitSet(b, typeB)
+  assert setA.len == setB.len
+  var setRes = newSeq[uint8](setA.len)
+  for i in 0 ..< setA.len:
+    setRes[i] = setA[i] or setB[i]
+
+  let valPos = c.values.len
+  c.values.add createTokenBuf()
+  c.values[valPos].bitSetToTokens(setRes, elementTyp, info)
+  result = cursorAt(c.values[valPos], 0)
+
 proc eval*(c: var EvalContext; n: var Cursor): Cursor =
   template propagateError(r: Cursor): Cursor =
     let val = r
@@ -408,6 +476,8 @@ proc eval*(c: var EvalContext; n: var Cursor): Cursor =
     of CallKinds:
       result = evalCall(c, n)
       skip n
+    of PlusSetX:
+      result = evalPlusSet(c, n)
     else:
       if n.tagId == ErrT:
         result = n

tests/nimony/const/tconstset.nim

@@ -1,8 +1,17 @@
 import std/assertions
 
+const a = {'a', 'b'}
+const b = {'0', '1'} + {'8', '9'}
+assert b == {'0', '1', '8', '9'}
+
+const c = a + {'x'}
+assert c == {'a', 'b', 'x'}
+
 const d = {'a'..'c'}
 assert d == {'a', 'b', 'c'}
 const e = {'0'..'3', '6'..'9', '3'..'7'}
 assert e == {'0'..'9'}
 const f = {5'i8..8, 9'i8..10}
 assert f == {5'i8, 6, 7, 8, 9, 10}
+const g = {1'i8..3} + {5'i8..8} + {10'i8..14'i8}
+assert g == {1'i8, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 14}