+redef class AExpr
+ # Get `self` as a `String`.
+ # Return null if not a string.
+ fun as_string: nullable String
+ do
+ if not self isa AStringFormExpr then return null
+ return self.value.as(not null)
+ end
+
+ # Get `self` as an `Int`.
+ # Return null if not an integer.
+ fun as_int: nullable Int
+ do
+ if not self isa AIntExpr then return null
+ return self.value.as(not null)
+ end
+
+ # Get `self` as a single identifier.
+ # Return null if not a single identifier.
+ fun as_id: nullable String
+ do
+ if self isa AMethidExpr then
+ return self.collect_text
+ end
+ if not self isa ACallExpr then return null
+ if not self.n_expr isa AImplicitSelfExpr then return null
+ if not self.n_args.n_exprs.is_empty then return null
+ return self.n_id.text
+ end
+end
+
+