1 files changed, 18 insertions, 12 deletions
diff --git a/compiler/treetab.nim b/compiler/treetab.nim
index 31cc76366..6685c4a89 100644
--- a/compiler/treetab.nim
+++ b/compiler/treetab.nim
@@ -9,8 +9,12 @@
 
 # Implements a table from trees to trees. Does structural equivalence checking.
 
-import
-  hashes, ast, astalgo, types
+import ast, astalgo, types
+
+import std/hashes
+
+when defined(nimPreviewSlimSystem):
+  import std/assertions
 
 proc hashTree*(n: PNode): Hash =
   if n.isNil:
@@ -54,7 +58,11 @@ proc treesEquivalent(a, b: PNode): bool =
         for i in 0..<a.len:
           if not treesEquivalent(a[i], b[i]): return
         result = true
+      else:
+        result = false
     if result: result = sameTypeOrNil(a.typ, b.typ)
+  else:
+    result = false
 
 proc nodeTableRawGet(t: TNodeTable, k: Hash, key: PNode): int =
   var h: Hash = k and high(t.data)
@@ -79,36 +87,34 @@ proc nodeTableRawInsert(data: var TNodePairSeq, k: Hash, key: PNode,
   data[h].val = val
 
 proc nodeTablePut*(t: var TNodeTable, key: PNode, val: int) =
-  var n: TNodePairSeq
-  var k: Hash = hashTree(key)
-  var index = nodeTableRawGet(t, k, key)
+  let k = hashTree(key)
+  let index = nodeTableRawGet(t, k, key)
   if index >= 0:
     assert(t.data[index].key != nil)
     t.data[index].val = val
   else:
     if mustRehash(t.data.len, t.counter):
-      newSeq(n, t.data.len * GrowthFactor)
+      var n = newSeq[TNodePair](t.data.len * GrowthFactor)
       for i in 0..high(t.data):
         if t.data[i].key != nil:
           nodeTableRawInsert(n, t.data[i].h, t.data[i].key, t.data[i].val)
-      swap(t.data, n)
+      t.data = move n
     nodeTableRawInsert(t.data, k, key, val)
     inc(t.counter)
 
 proc nodeTableTestOrSet*(t: var TNodeTable, key: PNode, val: int): int =
-  var n: TNodePairSeq
-  var k: Hash = hashTree(key)
-  var index = nodeTableRawGet(t, k, key)
+  let k = hashTree(key)
+  let index = nodeTableRawGet(t, k, key)
   if index >= 0:
     assert(t.data[index].key != nil)
     result = t.data[index].val
   else:
     if mustRehash(t.data.len, t.counter):
-      newSeq(n, t.data.len * GrowthFactor)
+      var n = newSeq[TNodePair](t.data.len * GrowthFactor)
       for i in 0..high(t.data):
         if t.data[i].key != nil:
           nodeTableRawInsert(n, t.data[i].h, t.data[i].key, t.data[i].val)
-      swap(t.data, n)
+      t.data = move n
     nodeTableRawInsert(t.data, k, key, val)
     result = val
     inc(t.counter)