base.BlockIf[R]

mut .return(a: mut base.ReturnStmt[R]): mut base.Block[R],
mut .error(info: mut base.ReturnStmt[imm base.Info]): mut base.Block[R],
mut .do(r: mut base.ReturnStmt[imm base.Void]): mut base.Block[R],
mut .return(a: mut base.ReturnStmt[R]): mut base.Block[R],
mut .error(info: mut base.ReturnStmt[imm base.Info]): mut base.Block[R],
mut .do(r: mut base.ReturnStmt[imm base.Void]): mut base.Block[R],