close #5540 generic object with generic field evaluated too early (#18062)

tests/misc/t5540.nim

@@ -0,0 +1,45 @@
+# bug #5540; works in 1.2.0
+# fails in 1.0 (Error: cannot generate VM code for)
+# fails in 0.18.0 (Error: type mismatch: got <type T>)
+
+block:
+  type
+    Fruit = object
+    Yellow = object
+      a: int
+  template getColor(x: typedesc[Fruit]): typedesc = Yellow
+  type
+    Banana[T] = object
+      b: T
+      a: getColor(Fruit)
+    Apple[T] = object
+      a: T
+      b: getColor(T)
+  block:
+    var x: Banana[int]
+    doAssert x.b == 0
+    doAssert x.a is Yellow
+  block:
+    var x: Apple[Fruit]
+    doAssert x.b is Yellow
+
+block:
+  type
+    Fruit = object
+    Yellow = object
+      a: int
+    
+  template getColor(x: typedesc[Fruit]): typedesc = Yellow
+
+  type
+    Banana[T] = object
+      b: T
+      a: getColor(Fruit)
+
+    Apple[T] = object
+      a: T
+      b: getColor(T)
+      
+  var x: Banana[int]
+  x.b = 13
+  x.a.a = 17