diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index fc3b520374..dcde4e2707 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -1587,20 +1587,24 @@ proc genInOp(p: BProc, e: PNode, d: var TLoc) =
                e.sons[2]
     initLocExpr(p, ea, a)
     initLoc(b, locExpr, e, OnUnknown)
-    b.r = rope("(")
     var length = sonsLen(e.sons[1])
-    for i in countup(0, length - 1):
-      let it = e.sons[1].sons[i]
-      if it.kind == nkRange:
-        initLocExpr(p, it.sons[0], x)
-        initLocExpr(p, it.sons[1], y)
-        addf(b.r, "$1 >= $2 && $1 <= $3",
-             [rdCharLoc(a), rdCharLoc(x), rdCharLoc(y)])
-      else:
-        initLocExpr(p, it, x)
-        addf(b.r, "$1 == $2", [rdCharLoc(a), rdCharLoc(x)])
-      if i < length - 1: add(b.r, " || ")
-    add(b.r, ")")
+    if length > 0:
+      b.r = rope("(")
+      for i in countup(0, length - 1):
+        let it = e.sons[1].sons[i]
+        if it.kind == nkRange:
+          initLocExpr(p, it.sons[0], x)
+          initLocExpr(p, it.sons[1], y)
+          addf(b.r, "$1 >= $2 && $1 <= $3",
+               [rdCharLoc(a), rdCharLoc(x), rdCharLoc(y)])
+        else:
+          initLocExpr(p, it, x)
+          addf(b.r, "$1 == $2", [rdCharLoc(a), rdCharLoc(x)])
+        if i < length - 1: add(b.r, " || ")
+      add(b.r, ")")
+    else:
+      # handle the case of an empty set
+      b.r = rope("0")
     putIntoDest(p, d, e, b.r)
   else:
     assert(e.sons[1].typ != nil)
diff --git a/compiler/lexer.nim b/compiler/lexer.nim
index cd2778d3c7..375bf227dd 100644
--- a/compiler/lexer.nim
+++ b/compiler/lexer.nim
@@ -344,7 +344,8 @@ proc getNumber(L: var TLexer, result: var TToken) =
       if buf[pos] == '_':
         if buf[pos+1] notin chars:
           lexMessage(L, errGenerated,
-            "only single underscores may occur in a token: '__' is invalid")
+            "only single underscores may occur in a token and token may not " &
+            "end with an underscore: e.g. '1__1' and '1_' are invalid")
           break
         add(tok.literal, '_')
         inc(pos)
diff --git a/compiler/sem.nim b/compiler/sem.nim
index 0adcccfbe5..b242e4db62 100644
--- a/compiler/sem.nim
+++ b/compiler/sem.nim
@@ -76,7 +76,7 @@ template semIdeForTemplateOrGeneric(c: PContext; n: PNode;
 proc fitNodePostMatch(c: PContext, formal: PType, arg: PNode): PNode =
   result = arg
   let x = result.skipConv
-  if x.kind in {nkPar, nkTupleConstr} and formal.kind != tyExpr:
+  if x.kind in {nkPar, nkTupleConstr, nkCurly} and formal.kind != tyExpr:
     changeType(c, x, formal, check=true)
   else:
     result = skipHiddenSubConv(result)
diff --git a/compiler/semexprs.nim b/compiler/semexprs.nim
index 5d6eaf6529..f5f5915d42 100644
--- a/compiler/semexprs.nim
+++ b/compiler/semexprs.nim
@@ -393,6 +393,8 @@ proc semIs(c: PContext, n: PNode, flags: TExprFlags): PNode =
       # When the right-hand side is an explicit type, we must
       # not allow regular values to be matched against the type:
       liftLhs = false
+  else:
+    n.sons[2] = semExpr(c, n[2])
 
   var lhsType = n[1].typ
   if lhsType.kind != tyTypeDesc:
@@ -906,19 +908,6 @@ proc buildEchoStmt(c: PContext, n: PNode): PNode =
 
 proc semExprNoType(c: PContext, n: PNode): PNode =
   result = semExpr(c, n, {efWantStmt})
-  # make an 'if' expression an 'if' statement again for backwards
-  # compatibility (.discardable was a bad idea!); bug #6980
-  var isStmt = false
-  if result.kind == nkIfExpr:
-    isStmt = true
-    for condActionPair in result:
-      let action = condActionPair.lastSon
-      if not implicitlyDiscardable(action) and not
-          endsInNoReturn(action):
-        isStmt = false
-    if isStmt:
-      result.kind = nkIfStmt
-      result.typ = nil
   discardCheck(c, result)
 
 proc isTypeExpr(n: PNode): bool =
diff --git a/compiler/semgnrc.nim b/compiler/semgnrc.nim
index 0218096d6e..e3c750f5b7 100644
--- a/compiler/semgnrc.nim
+++ b/compiler/semgnrc.nim
@@ -54,7 +54,8 @@ template macroToExpand(s): untyped =
   s.kind in {skMacro, skTemplate} and (s.typ.len == 1 or sfAllUntyped in s.flags)
 
 template macroToExpandSym(s): untyped =
-  s.kind in {skMacro, skTemplate} and (s.typ.len == 1) and not fromDotExpr
+  sfCustomPragma notin s.flags and s.kind in {skMacro, skTemplate} and
+    (s.typ.len == 1) and not fromDotExpr
 
 template isMixedIn(sym): bool =
   let s = sym
diff --git a/compiler/semstmts.nim b/compiler/semstmts.nim
index 945bcd9e17..bf004a5314 100644
--- a/compiler/semstmts.nim
+++ b/compiler/semstmts.nim
@@ -111,13 +111,15 @@ proc semExprBranchScope(c: PContext, n: PNode): PNode =
 const
   skipForDiscardable = {nkIfStmt, nkIfExpr, nkCaseStmt, nkOfBranch,
     nkElse, nkStmtListExpr, nkTryStmt, nkFinally, nkExceptBranch,
-    nkElifBranch, nkElifExpr, nkElseExpr, nkBlockStmt, nkBlockExpr}
+    nkElifBranch, nkElifExpr, nkElseExpr, nkBlockStmt, nkBlockExpr,
+    nkHiddenStdConv}
 
 proc implicitlyDiscardable(n: PNode): bool =
   var n = n
   while n.kind in skipForDiscardable: n = n.lastSon
-  result = isCallExpr(n) and n.sons[0].kind == nkSym and
-           sfDiscardable in n.sons[0].sym.flags
+  result = n.kind == nkRaiseStmt or
+           (isCallExpr(n) and n.sons[0].kind == nkSym and
+           sfDiscardable in n.sons[0].sym.flags)
 
 proc fixNilType(c: PContext; n: PNode) =
   if isAtom(n):
@@ -132,11 +134,8 @@ proc discardCheck(c: PContext, result: PNode) =
   if c.matchedConcept != nil: return
   if result.typ != nil and result.typ.kind notin {tyStmt, tyVoid}:
     if implicitlyDiscardable(result):
-      var n = result
-      result.typ = nil
-      while n.kind in skipForDiscardable:
-        n = n.lastSon
-        n.typ = nil
+      var n = newNodeI(nkDiscardStmt, result.info, 1)
+      n[0] = result
     elif result.typ.kind != tyError and c.config.cmd != cmdInteractive:
       var n = result
       while n.kind in skipForDiscardable: n = n.lastSon
diff --git a/compiler/types.nim b/compiler/types.nim
index c5af855cc5..4d3f99c310 100644
--- a/compiler/types.nim
+++ b/compiler/types.nim
@@ -623,7 +623,7 @@ proc firstOrd*(conf: ConfigRef; t: PType): BiggestInt =
       assert(t.n.sons[0].kind == nkSym)
       result = t.n.sons[0].sym.position
   of tyGenericInst, tyDistinct, tyTypeDesc, tyAlias, tySink,
-     tyStatic, tyInferred, tyUserTypeClassInst:
+     tyStatic, tyInferred, tyUserTypeClasses:
     result = firstOrd(conf, lastSon(t))
   of tyOrdinal:
     if t.len > 0: result = firstOrd(conf, lastSon(t))
@@ -642,7 +642,7 @@ proc firstFloat*(t: PType): BiggestFloat =
     getFloatValue(t.n.sons[0])
   of tyVar: firstFloat(t.sons[0])
   of tyGenericInst, tyDistinct, tyTypeDesc, tyAlias, tySink,
-     tyStatic, tyInferred:
+     tyStatic, tyInferred, tyUserTypeClasses:
     firstFloat(lastSon(t))
   else:
     internalError(newPartialConfigRef(), "invalid kind for firstFloat(" & $t.kind & ')')
@@ -679,7 +679,7 @@ proc lastOrd*(conf: ConfigRef; t: PType; fixedUnsigned = false): BiggestInt =
     assert(t.n.sons[sonsLen(t.n) - 1].kind == nkSym)
     result = t.n.sons[sonsLen(t.n) - 1].sym.position
   of tyGenericInst, tyDistinct, tyTypeDesc, tyAlias, tySink,
-     tyStatic, tyInferred:
+     tyStatic, tyInferred, tyUserTypeClasses:
     result = lastOrd(conf, lastSon(t))
   of tyProxy: result = 0
   of tyOrdinal:
@@ -699,7 +699,7 @@ proc lastFloat*(t: PType): BiggestFloat =
     assert(t.n.kind == nkRange)
     getFloatValue(t.n.sons[1])
   of tyGenericInst, tyDistinct, tyTypeDesc, tyAlias, tySink,
-     tyStatic, tyInferred:
+     tyStatic, tyInferred, tyUserTypeClasses:
     lastFloat(lastSon(t))
   else:
     internalError(newPartialConfigRef(), "invalid kind for lastFloat(" & $t.kind & ')')
@@ -707,7 +707,7 @@ proc lastFloat*(t: PType): BiggestFloat =
 
 
 proc lengthOrd*(conf: ConfigRef; t: PType): BiggestInt =
-  case t.kind
+  case t.skipTypes(tyUserTypeClasses).kind
   of tyInt64, tyInt32, tyInt: result = lastOrd(conf, t)
   of tyDistinct: result = lengthOrd(conf, t.sons[0])
   else:
@@ -717,7 +717,7 @@ proc lengthOrd*(conf: ConfigRef; t: PType): BiggestInt =
     if last == high(BiggestInt) and first <= 0:
       result = last
     else:
-      result = lastOrd(conf, t) - firstOrd(conf, t) + 1
+      result = last - first + 1
 
 # -------------- type equality -----------------------------------------------
 
diff --git a/compiler/vm.nim b/compiler/vm.nim
index b16eb0fd40..7f0dd80edc 100644
--- a/compiler/vm.nim
+++ b/compiler/vm.nim
@@ -209,7 +209,7 @@ proc writeField(n: var PNode, x: TFullReg) =
   of rkNone: discard
   of rkInt: n.intVal = x.intVal
   of rkFloat: n.floatVal = x.floatVal
-  of rkNode: n = x.node
+  of rkNode: n = copyValue(x.node)
   of rkRegisterAddr: writeField(n, x.regAddr[])
   of rkNodeAddr: n = x.nodeAddr[]
 
@@ -622,6 +622,13 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
             stackTrace(c, tos, pc, errNilAccess)
           regs[ra].nodeAddr[][] = n[]
           regs[ra].nodeAddr[].flags.incl nfIsRef
+        # `var object` parameters are sent as rkNodeAddr. When they are mutated
+        # vmgen generates opcWrDeref, which means that we must dereference
+        # twice.
+        # TODO: This should likely be handled differently in vmgen.
+        elif (nfIsRef notin regs[ra].nodeAddr[].flags and
+            nfIsRef notin n.flags):
+          regs[ra].nodeAddr[][] = n[]
         else:
           regs[ra].nodeAddr[] = n
       of rkRegisterAddr: regs[ra].regAddr[] = regs[rc]
@@ -912,6 +919,7 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
       if a.kind == nkSym:
         regs[ra].node = if a.sym.ast.isNil: newNode(nkNilLit)
                         else: copyTree(a.sym.ast)
+        regs[ra].node.flags.incl nfIsRef
       else:
         stackTrace(c, tos, pc, "node is not a symbol")
     of opcEcho:
@@ -1210,8 +1218,14 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
     of opcIsNil:
       decodeB(rkInt)
       let node = regs[rb].node
-      regs[ra].intVal = ord(node.kind == nkNilLit or
-        (node.kind in {nkStrLit..nkTripleStrLit} and node.strVal.isNil))
+      regs[ra].intVal = ord(
+        # Note that `nfIsRef` + `nkNilLit` represents an allocated
+        # reference with the value `nil`, so `isNil` should be false!
+        (node.kind == nkNilLit and nfIsRef notin node.flags) or
+        (node.kind in {nkStrLit..nkTripleStrLit} and node.strVal.isNil) or
+        (not node.typ.isNil and node.typ.kind == tyProc and
+          node.typ.callConv == ccClosure and node.sons[0].kind == nkNilLit and
+          node.sons[1].kind == nkNilLit))
     of opcNBindSym:
       decodeBx(rkNode)
       regs[ra].node = copyTree(c.constants.sons[rbx])
@@ -1462,6 +1476,7 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
       else:
         regs[ra].node = newNodeI(nkIdent, c.debug[pc])
         regs[ra].node.ident = getIdent(c.cache, regs[rb].node.strVal)
+        regs[ra].node.flags.incl nfIsRef
     of opcSetType:
       if regs[ra].kind != rkNode:
         internalError(c.config, c.debug[pc], "cannot set type")
diff --git a/lib/impure/nre.nim b/lib/impure/nre.nim
index 6058128ddf..889210f627 100644
--- a/lib/impure/nre.nim
+++ b/lib/impure/nre.nim
@@ -654,17 +654,17 @@ template replaceImpl(str: string, pattern: Regex,
 
 proc replace*(str: string, pattern: Regex,
               subproc: proc (match: RegexMatch): string): string =
-  ## Replaces each match of Regex in the string with ``sub``, which should
+  ## Replaces each match of Regex in the string with ``subproc``, which should
   ## never be or return ``nil``.
   ##
-  ## If ``sub`` is a ``proc (RegexMatch): string``, then it is executed with
+  ## If ``subproc`` is a ``proc (RegexMatch): string``, then it is executed with
   ## each match and the return value is the replacement value.
   ##
-  ## If ``sub`` is a ``proc (string): string``, then it is executed with the
+  ## If ``subproc`` is a ``proc (string): string``, then it is executed with the
   ## full text of the match and and the return value is the replacement
   ## value.
   ##
-  ## If ``sub`` is a string, the syntax is as follows:
+  ## If ``subproc`` is a string, the syntax is as follows:
   ##
   ## -  ``$$`` - literal ``$``
   ## -  ``$123`` - capture number ``123``
diff --git a/lib/pure/osproc.nim b/lib/pure/osproc.nim
index e8bca4bdd1..f86acfc492 100644
--- a/lib/pure/osproc.nim
+++ b/lib/pure/osproc.nim
@@ -884,11 +884,9 @@ elif not defined(useNimRtl):
         chck posix_spawn_file_actions_adddup2(fops, data.pStdin[readIdx], readIdx)
         chck posix_spawn_file_actions_addclose(fops, data.pStdout[readIdx])
         chck posix_spawn_file_actions_adddup2(fops, data.pStdout[writeIdx], writeIdx)
-        chck posix_spawn_file_actions_addclose(fops, data.pStderr[readIdx])
         if (poStdErrToStdOut in data.options):
+          chck posix_spawn_file_actions_addclose(fops, data.pStderr[readIdx])
           chck posix_spawn_file_actions_adddup2(fops, data.pStdout[writeIdx], 2)
-        else:
-          chck posix_spawn_file_actions_adddup2(fops, data.pStderr[writeIdx], 2)
 
       var res: cint
       if data.workingDir.len > 0:
diff --git a/lib/pure/strformat.nim b/lib/pure/strformat.nim
index 36404cdf7c..247b9ec5cb 100644
--- a/lib/pure/strformat.nim
+++ b/lib/pure/strformat.nim
@@ -258,7 +258,9 @@ template callFormat(res, arg) {.dirty.} =
     # workaround in order to circumvent 'strutils.format' which matches
     # too but doesn't adhere to our protocol.
     res.add arg
-  elif compiles(format(arg, res)):
+  elif compiles(format(arg, res)) and
+      # Check if format returns void
+      not (compiles do: discard format(arg, res)):
     format(arg, res)
   elif compiles(format(arg)):
     res.add format(arg)
@@ -684,6 +686,9 @@ when isMainModule:
   var nullTime: DateTime
   check &"{nullTime:yyyy-mm-dd}", "0000-00-00"
 
+  var tm = fromUnix(0)
+  discard &"{tm}"
+
   # Unicode string tests
   check &"""{"αβγ"}""", "αβγ"
   check &"""{"αβγ":>5}""", "  αβγ"
diff --git a/lib/pure/times.nim b/lib/pure/times.nim
index 7fd60b818f..a134faef2d 100644
--- a/lib/pure/times.nim
+++ b/lib/pure/times.nim
@@ -489,18 +489,16 @@ proc toParts*(dur: Duration): DurationParts =
 
     result[unit] = quantity
 
-proc stringifyUnit*(value: int | int64, unit: string): string =
+proc stringifyUnit(value: int | int64, unit: TimeUnit): string =
   ## Stringify time unit with it's name, lowercased
-  runnableExamples:
-    doAssert stringifyUnit(2, "Seconds") == "2 seconds"
-    doAssert stringifyUnit(1, "Years") == "1 year"
+  let strUnit = $unit
   result = ""
   result.add($value)
   result.add(" ")
   if abs(value) != 1:
-    result.add(unit.toLowerAscii())
+    result.add(strUnit.toLowerAscii())
   else:
-    result.add(unit[0..^2].toLowerAscii())
+    result.add(strUnit[0..^2].toLowerAscii())
 
 proc humanizeParts(parts: seq[string]): string =
   ## Make date string parts human-readable
@@ -530,7 +528,7 @@ proc `$`*(dur: Duration): string =
   for unit in countdown(Weeks, Nanoseconds):
     let quantity = numParts[unit]
     if quantity != 0.int64:
-      parts.add(stringifyUnit(quantity, $unit))
+      parts.add(stringifyUnit(quantity, unit))
 
   result = humanizeParts(parts)
 
@@ -1024,7 +1022,7 @@ proc `$`*(ti: TimeInterval): string =
   var tiParts = toParts(ti)
   for unit in countdown(Years, Nanoseconds):
     if tiParts[unit] != 0:
-      parts.add(stringifyUnit(tiParts[unit], $unit))
+      parts.add(stringifyUnit(tiParts[unit], unit))
 
   result = humanizeParts(parts)
 
diff --git a/tests/concepts/t7952.nim b/tests/concepts/t7952.nim
new file mode 100644
index 0000000000..96ff47e4a7
--- /dev/null
+++ b/tests/concepts/t7952.nim
@@ -0,0 +1,12 @@
+discard """
+  output: 5
+"""
+
+type
+  HasLen = concept iter
+    len(iter) is int
+
+proc echoLen(x: HasLen) =
+  echo len(x)
+
+echoLen([1, 2, 3, 4, 5])
diff --git a/tests/exprs/tstmtexprs.nim b/tests/exprs/tstmtexprs.nim
index 577f314ec2..e91c204586 100644
--- a/tests/exprs/tstmtexprs.nim
+++ b/tests/exprs/tstmtexprs.nim
@@ -151,3 +151,13 @@ if true:
   fooBool()
 else:
   raise newException(ValueError, "argh")
+
+# bug #5374
+
+proc test1(): int64 {.discardable.} = discard
+proc test2(): int {.discardable.} = discard
+
+if true:
+  test1()
+else:
+  test2()
diff --git a/tests/iter/t8041.nim b/tests/iter/t8041.nim
new file mode 100644
index 0000000000..c87134cfca
--- /dev/null
+++ b/tests/iter/t8041.nim
@@ -0,0 +1,7 @@
+iterator xy[T](a: T, b: set[T]): T =
+  if a in b:
+    yield a
+
+for a in xy(1'i8, {}):
+  for b in xy(a, {}):
+    echo a
diff --git a/tests/pragmas/tcustom_pragma.nim b/tests/pragmas/tcustom_pragma.nim
index 33a4a7e65e..cd1edccf67 100644
--- a/tests/pragmas/tcustom_pragma.nim
+++ b/tests/pragmas/tcustom_pragma.nim
@@ -137,4 +137,12 @@ block:
   static:
     assert hasIntSerKey
     assert strSerKey == "string"
-    assert nestedItemDefVal == "Nimmers of the world, unite!"
\ No newline at end of file
+    assert nestedItemDefVal == "Nimmers of the world, unite!"
+
+block:
+  template simpleAttr {.pragma.}
+
+  type Annotated {.simpleAttr.} = object
+
+  proc generic_proc[T]() =
+    assert Annotated.hasCustomPragma(simpleAttr)
\ No newline at end of file
diff --git a/tests/sets/t2669.nim b/tests/sets/t2669.nim
new file mode 100644
index 0000000000..6b8eb0f54c
--- /dev/null
+++ b/tests/sets/t2669.nim
@@ -0,0 +1,6 @@
+discard """
+line: 6
+errormsg: "cannot convert 6 to range 1..5(int8)"
+"""
+
+var c: set[range[1i8..5i8]] = {1i8, 2i8, 6i8}
diff --git a/tests/vm/tvmmisc.nim b/tests/vm/tvmmisc.nim
index 80f5aeee00..6a8084647f 100644
--- a/tests/vm/tvmmisc.nim
+++ b/tests/vm/tvmmisc.nim
@@ -89,4 +89,62 @@ block:
     proc f(size: int): int =
       var some = newStringOfCap(size)
       result = size
-    doAssert f(4) == 4
\ No newline at end of file
+    doAssert f(4) == 4
+
+# #6689
+block:
+  static:
+    proc foo(): int = 0
+    var f: proc(): int
+    doAssert f.isNil
+    f = foo
+    doAssert(not f.isNil)
+
+block:
+  static:
+    var x: ref ref int
+    new(x)
+    doAssert(not x.isNil)
+
+# #7871
+static:
+  type Obj = object
+    field: int
+  var s = newSeq[Obj](1)
+  var o = Obj()
+  s[0] = o
+  o.field = 2
+  doAssert s[0].field == 0
+
+# #8125
+static:
+   let def_iter_var = ident("it")
+
+# #8142
+static:
+  type Obj = object
+    names: string
+
+  proc pushName(o: var Obj) =
+    var s = ""
+    s.add("FOOBAR")
+    o.names.add(s)
+
+  var o = Obj()
+  o.names = ""
+  o.pushName()
+  o.pushName()
+  doAssert o.names == "FOOBARFOOBAR"
+
+# #8154
+import parseutils
+
+static:
+  type Obj = object
+    i: int
+
+  proc foo(): Obj =
+    discard parseInt("1", result.i, 0)
+
+  static:
+    doAssert foo().i == 1