diff --git a/src/exec.cpp b/src/exec.cpp
index 5325e872a..5c6f36f68 100644
--- a/src/exec.cpp
+++ b/src/exec.cpp
@@ -382,45 +382,17 @@ static bool exec_internal_builtin_proc(parser_t &parser, const std::shared_ptr<j
     // If this is the first process, check the io redirections and see where we should
     // be reading from.
     if (pipe_read) {
-        local_builtin_stdin = pipe_read->pipe_fd();
+        local_builtin_stdin = pipe_read->source_fd;
     } else if (const auto in = proc_io_chain.io_for_fd(STDIN_FILENO)) {
-        switch (in->io_mode) {
-            case io_mode_t::fd: {
-                const io_fd_t *in_fd = static_cast<const io_fd_t *>(in.get());
-                // Ignore fd redirections from an fd other than the
-                // standard ones. e.g. in source <&3 don't actually read from fd 3,
-                // which is internal to fish. We still respect this redirection in
-                // that we pass it on as a block IO to the code that source runs,
-                // and therefore this is not an error.
-                if (in_fd->source_fd >= 0 && in_fd->source_fd < 3) {
-                    local_builtin_stdin = in_fd->source_fd;
-                }
-                break;
-            }
-            case io_mode_t::pipe: {
-                const io_pipe_t *in_pipe = static_cast<const io_pipe_t *>(in.get());
-                if (in_pipe->fd == STDIN_FILENO) {
-                    local_builtin_stdin = in_pipe->pipe_fd();
-                }
-                break;
-            }
-            case io_mode_t::file: {
-                const io_file_t *in_file = static_cast<const io_file_t *>(in.get());
-                local_builtin_stdin = in_file->file_fd();
-                break;
-            }
-            case io_mode_t::close: {
-                // FIXME: When requesting that stdin be closed, we really don't do
-                // anything. How should this be handled?
-                local_builtin_stdin = -1;
-
-                break;
-            }
-            default: {
-                local_builtin_stdin = -1;
-                debug(1, _(L"Unknown input redirection type %d"), in->io_mode);
-                break;
-            }
+        // Ignore fd redirections from an fd other than the
+        // standard ones. e.g. in source <&3 don't actually read from fd 3,
+        // which is internal to fish. We still respect this redirection in
+        // that we pass it on as a block IO to the code that source runs,
+        // and therefore this is not an error.
+        bool ignore_redirect =
+            in->io_mode == io_mode_t::fd && in->source_fd >= 0 && in->source_fd < 3;
+        if (!ignore_redirect) {
+            local_builtin_stdin = in->source_fd;
         }
     }
 
diff --git a/src/io.cpp b/src/io.cpp
index b00800c0d..9fa759f0d 100644
--- a/src/io.cpp
+++ b/src/io.cpp
@@ -28,11 +28,11 @@
 #define OPEN_MASK 0666
 
 io_data_t::~io_data_t() = default;
-
-io_file_t::io_file_t(int f, autoclose_fd_t file)
-    : io_data_t(io_mode_t::file, f, file_fd_.fd()), file_fd_(std::move(file)) {
-    assert(file_fd_.valid() && "File is not valid");
-}
+io_pipe_t::~io_pipe_t() = default;
+io_fd_t::~io_fd_t() = default;
+io_close_t::~io_close_t() = default;
+io_file_t::~io_file_t() = default;
+io_bufferfill_t::~io_bufferfill_t() = default;
 
 void io_close_t::print() const { std::fwprintf(stderr, L"close %d\n", fd); }
 
@@ -41,7 +41,7 @@ void io_fd_t::print() const { std::fwprintf(stderr, L"FD map %d -> %d\n", source
 void io_file_t::print() const { std::fwprintf(stderr, L"file (%d)\n", file_fd_.fd()); }
 
 void io_pipe_t::print() const {
-    std::fwprintf(stderr, L"pipe {%d} (input: %s)\n", pipe_fd(), is_input_ ? "yes" : "no");
+    std::fwprintf(stderr, L"pipe {%d} (input: %s)\n", source_fd, is_input_ ? "yes" : "no");
 }
 
 void io_bufferfill_t::print() const { std::fwprintf(stderr, L"bufferfill {%d}\n", write_fd_.fd()); }
@@ -207,12 +207,6 @@ std::shared_ptr<io_buffer_t> io_bufferfill_t::finish(std::shared_ptr<io_bufferfi
     return buffer;
 }
 
-io_pipe_t::~io_pipe_t() = default;
-io_fd_t::~io_fd_t() = default;
-io_close_t::~io_close_t() = default;
-io_file_t::~io_file_t() = default;
-io_bufferfill_t::~io_bufferfill_t() = default;
-
 io_buffer_t::~io_buffer_t() {
     assert(!fillthread_running() && "io_buffer_t destroyed with outstanding fillthread");
 }
diff --git a/src/io.h b/src/io.h
index b5319e70a..7503b664e 100644
--- a/src/io.h
+++ b/src/io.h
@@ -215,12 +215,13 @@ class io_file_t : public io_data_t {
    public:
     void print() const override;
 
-    io_file_t(int f, autoclose_fd_t file);
+    io_file_t(int fd, autoclose_fd_t file)
+        : io_data_t(io_mode_t::file, fd, file.fd()), file_fd_(std::move(file)) {
+        assert(file_fd_.valid() && "File is not valid");
+    }
 
     ~io_file_t() override;
 
-    int file_fd() const { return file_fd_.fd(); }
-
    private:
     // The fd for the file which we are writing to or reading from.
     autoclose_fd_t file_fd_;
@@ -240,11 +241,11 @@ class io_pipe_t : public io_data_t {
     io_pipe_t(int fd, bool is_input, autoclose_fd_t pipe_fd)
         : io_data_t(io_mode_t::pipe, fd, pipe_fd.fd()),
           pipe_fd_(std::move(pipe_fd)),
-          is_input_(is_input) {}
+          is_input_(is_input) {
+        assert(pipe_fd_.valid() && "Pipe is not valid");
+    }
 
     ~io_pipe_t() override;
-
-    int pipe_fd() const { return pipe_fd_.fd(); }
 };
 
 class io_buffer_t;
@@ -267,15 +268,14 @@ class io_bufferfill_t : public io_data_t {
     io_bufferfill_t(autoclose_fd_t write_fd, std::shared_ptr<io_buffer_t> buffer)
         : io_data_t(io_mode_t::bufferfill, STDOUT_FILENO, write_fd.fd()),
           write_fd_(std::move(write_fd)),
-          buffer_(std::move(buffer)) {}
+          buffer_(std::move(buffer)) {
+        assert(write_fd_.valid() && "fd is not valid");
+    }
 
     ~io_bufferfill_t() override;
 
     std::shared_ptr<io_buffer_t> buffer() const { return buffer_; }
 
-    /// \return the fd that, when written to, fills the buffer.
-    int write_fd() const { return write_fd_.fd(); }
-
     /// Create an io_bufferfill_t which, when written from, fills a buffer with the contents.
     /// \returns nullptr on failure, e.g. too many open fds.
     ///
diff --git a/src/redirection.cpp b/src/redirection.cpp
index 059dd65a4..92a01d04a 100644
--- a/src/redirection.cpp
+++ b/src/redirection.cpp
@@ -35,37 +35,11 @@ int redirection_spec_t::oflags() const {
 dup2_list_t dup2_list_t::resolve_chain(const io_chain_t &io_chain) {
     ASSERT_IS_NOT_FORKED_CHILD();
     dup2_list_t result;
-    for (const auto &io_ref : io_chain) {
-        switch (io_ref->io_mode) {
-            case io_mode_t::file: {
-                const io_file_t *io = static_cast<const io_file_t *>(io_ref.get());
-                result.add_dup2(io->file_fd(), io->fd);
-                break;
-            }
-
-            case io_mode_t::close: {
-                const io_close_t *io = static_cast<const io_close_t *>(io_ref.get());
-                result.add_close(io->fd);
-                break;
-            }
-
-            case io_mode_t::fd: {
-                const io_fd_t *io = static_cast<const io_fd_t *>(io_ref.get());
-                result.add_dup2(io->source_fd, io->fd);
-                break;
-            }
-
-            case io_mode_t::pipe: {
-                const io_pipe_t *io = static_cast<const io_pipe_t *>(io_ref.get());
-                result.add_dup2(io->pipe_fd(), io->fd);
-                break;
-            }
-
-            case io_mode_t::bufferfill: {
-                const io_bufferfill_t *io = static_cast<const io_bufferfill_t *>(io_ref.get());
-                result.add_dup2(io->write_fd(), io->fd);
-                break;
-            }
+    for (const auto &io : io_chain) {
+        if (io->source_fd < 0) {
+            result.add_close(io->fd);
+        } else {
+            result.add_dup2(io->source_fd, io->fd);
         }
     }
     return result;