close #3482 no more cgen error with typed templates (#18094)

Author: timotheecour

tests/misc/t3482.nim

@@ -0,0 +1,15 @@
+discard """
+  action: reject
+  nimout: "t3482.nim(13, 8) Error: undeclared identifier: 'output'"
+"""
+# bug #3482 (correct behavior since 1.4.0, cgen error in 1.2.0)
+template foo*(body: typed) =
+  if true:
+    body
+
+proc test =
+  foo:
+    var output = ""
+  echo output.len
+
+test()