From 64aec6eb85b79f21c9da1d9d0c475942514180c5 Mon Sep 17 00:00:00 2001
From: Andreas Rumpf <rumpf_a@web.de>
Date: Tue, 4 Aug 2020 12:45:15 +0200
Subject: [PATCH] fixes a collect() bug reported on the forum (#15156)
 [backport:1.2]

---
 compiler/semstmts.nim      |  2 +-
 compiler/varpartitions.nim |  2 +-
 lib/pure/sugar.nim         | 10 ++++++++++
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index 68f0cee644..1315e8960c 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -159,7 +159,7 @@ proc semIf(c: PContext, n: PNode; flags: TExprFlags): PNode =
     if it.len == 2:
       openScope(c)
       it[0] = forceBool(c, semExprWithType(c, it[0]))
-      it[1] = semExprBranch(c, it[1])
+      it[1] = semExprBranch(c, it[1], flags)
       typ = commonType(typ, it[1])
       closeScope(c)
     elif it.len == 1:
diff --git a/compiler/varpartitions.nim b/compiler/varpartitions.nim
index 4535c9aac2..6857e1b57a 100644
--- a/compiler/varpartitions.nim
+++ b/compiler/varpartitions.nim
@@ -11,7 +11,7 @@
 ## Nim's write tracking and also for the cursor inference.
 ## The algorithm is a reinvention / variation of Steensgaard's
 ## algorithm.
-## The used algorithm is "union find" with path compression.
+## The used data structure is "union find" with path compression.
 
 import ast, types, lineinfos, options, msgs, renderer
 from trees import getMagic
diff --git a/lib/pure/sugar.nim b/lib/pure/sugar.nim
index d2bdb0fdca..00f4de5d86 100644
--- a/lib/pure/sugar.nim
+++ b/lib/pure/sugar.nim
@@ -394,3 +394,13 @@ when isMainModule:
         of "bird": "word"
         else: d
     assert z == @["word", "word"]
+
+
+    proc tforum =
+      let ans = collect(newSeq):
+        for y in 0..10:
+          if y mod 5 == 2:
+            for x in 0..y:
+              x
+
+    tforum()