fixes #1803

tests/iter/tshallowcopy_closures.nim

@@ -0,0 +1,31 @@
+discard """
+  ccodecheck: "!@('{' \\s* 'NI HEX3Astate;' \\s* '}')"
+"""
+
+# bug #1803
+type TaskFn = iterator (): float
+
+iterator a1(): float {.closure.} =
+    var k = 10
+    while k > 0:
+        echo "a1 ", k
+        dec k
+        yield 1.0
+
+
+iterator a2(): float {.closure.} =
+    var k = 15
+    while k > 0:
+        echo "a2 ", k
+        dec k
+        yield 2.0
+
+var
+  x = a1
+  y = a2
+  z: TaskFn
+
+discard x()
+z = x #shallowCopy(z, x)
+z = y #shallowCopy(z, y)
+discard x()