add test for #3907 (#21069)

* add test for #3907

tests/misc/t3907.nim

@@ -0,0 +1,10 @@
+import std/assertions
+
+let a = 0
+let b = if false: -1 else: a
+doAssert b == 0
+
+let c: range[0..high(int)] = 0
+let d = if false: -1 else: c
+
+doAssert d == 0