add tests for recently closed issues (#10722)

tests/iter/titer12.nim

@@ -0,0 +1,82 @@
+discard """
+output: '''
+Selecting 2
+1.0
+Selecting 4
+2.0
+'''
+"""
+
+
+# bug #5522
+import macros, sugar, sequtils
+
+proc tryS(f: () -> void): void =
+  (try: f() except: discard)
+
+template trySTImpl(body: untyped): untyped =
+  tryS do() -> auto:
+    `body`
+
+macro tryST*(body: untyped): untyped =
+  var b = if body.kind == nnkDo: body[^1] else: body
+  result = quote do:
+    trySTImpl((block:
+      `b`
+    ))
+
+iterator testIt(): int {.closure.} =
+  for x in 0..10:
+    yield x
+
+var xs = newSeq[int]()
+proc test = tryST do:
+  for x in testIt():
+    xs.add(x)
+
+test()
+
+doAssert xs == toSeq(0..10)
+
+
+
+# bug #5690
+proc filter[T](it: (iterator : T), f: proc(x: T): bool): (iterator : T) =
+  return iterator (): T {.closure.} =
+    for x in it():
+      if f(x): 
+        yield x
+
+proc len[T](it : iterator : T) : Natural =
+  for i in it():
+    result += 1
+
+proc simpleSeqIterator(s :seq[int]) : iterator : int =
+  iterator it: int {.closure.} =
+    for x in s:
+      yield x
+  result = it
+
+let a = newSeq[int](99)
+
+doAssert len(simpleSeqIterator(a).filter(proc(x : int) : bool = true)) == 99
+
+
+
+# bug #5340
+proc where[A](input: seq[A], filter: (A) -> bool): iterator (): A =
+  result = iterator (): A {.closure.} = 
+    for item in input:
+      if filter(item):
+        yield item
+
+proc select[A,B](input: iterator(): A {.closure.}, selector: (A) -> B): iterator (): B {.closure.} = 
+  result = iterator (): B =
+    for item in input():
+      echo "Selecting " & $item
+      yield selector(item)
+
+let query = @[1,2,3,4].where(x=>x mod 2==0).select((x)=>x/2)
+
+for i in query():
+  echo $i