fixes #1562, fixes #1543

tests/template/twrongmapit.nim

@@ -0,0 +1,32 @@
+discard """
+  errormsg: "'"
+  file: "sequtils.nim"
+  line: 416
+"""
+# unfortunately our tester doesn't support multiple lines of compiler
+# error messages yet...
+
+# bug #1562
+type Foo* {.pure, final.} = object
+  elt: float
+
+template defineOpAssign(T: expr, op: expr) {.immediate.} =
+  proc op*(v: var T, w: T) {.inline.} =
+    for i in 0..1:
+      op(v.elt, w.elt)
+
+const ATTEMPT = 0
+
+when ATTEMPT == 0:
+  # FAILS: defining `/=` with template calling template
+  # ERROR about sem.nim line 144
+  template defineOpAssigns(T: expr) {.immediate.} =
+    mixin `/=`
+    defineOpAssign(T, `/=`)
+
+  defineOpAssigns(Foo)
+
+# bug #1543
+import sequtils
+
+(var i= @[""];i).mapIt(it)