Rewrite the core of the binding generator.

TL;DR: The binding generator is a mess as of right now. At first it was funny
(in a "this is challenging" sense) to improve on it, but this is not
sustainable.

The truth is that the current architecture of the binding generator is a huge
pile of hacks, so these few days I've been working on rewriting it with a few
goals.

 1) Have the hacks as contained and identified as possible. They're sometimes
    needed because how clang exposes the AST, but ideally those hacks are well
    identified and don't interact randomly with each others.

    As an example, in the current bindgen when scanning the parameters of a
    function that references a struct clones all the struct information, then if
    the struct name changes (because we mangle it), everything breaks.

 2) Support extending the bindgen output without having to deal with clang. The
    way I'm aiming to do this is separating completely the parsing stage from
    the code generation one, and providing a single id for each item the binding
    generator provides.

 3) No more random mutation of the internal representation from anywhere. That
    means no more Rc<RefCell<T>>, no more random circular references, no more
    borrow_state... nothing.

 4) No more deduplication of declarations before code generation.

    Current bindgen has a stage, called `tag_dup_decl`[1], that takes care of
    deduplicating declarations. That's completely buggy, and for C++ it's a
    complete mess, since we YOLO modify the world.

    I've managed to take rid of this using the clang canonical declaration, and
    the definition, to avoid scanning any type/item twice.

 5) Code generation should not modify any internal data structure. It can lookup
    things, traverse whatever it needs, but not modifying randomly.

 6) Each item should have a canonical name, and a single source of mangling
    logic, and that should be computed from the inmutable state, at code
    generation.

    I've put a few canonical_name stuff in the code generation phase, but it's
    still not complete, and should change if I implement namespaces.

Improvements pending until this can land:

 1) Add support for missing core stuff, mainly generating functions (note that
    we parse the signatures for types correctly though), bitfields, generating
    C++ methods.

 2) Add support for the necessary features that were added to work around some
    C++ pitfalls, like opaque types, etc...

 3) Add support for the sugar that Manish added recently.

 4) Optionally (and I guess this can land without it, because basically nobody
    uses it since it's so buggy), bring back namespace support.

These are not completely trivial, but I think I can do them quite easily with
the current architecture.

I'm putting the current state of affairs here as a request for comments... Any
thoughts? Note that there are still a few smells I want to eventually
re-redesign, like the ParseError::Recurse thing, but until that happens I'm
way happier with this kind of architecture.

I'm keeping the old `parser.rs` and `gen.rs` in tree just for reference while I
code, but they will go away.

[1]: https://github.com/Yamakaky/rust-bindgen/blob/master/src/gen.rs#L448

1 files changed, 141 insertions, 0 deletions

diff --git a/src/ir/annotations.rs b/src/ir/annotations.rs
new file mode 100644
index 00000000..cc61dbfd
--- /dev/null
+++ b/src/ir/annotations.rs
@@ -0,0 +1,141 @@
+use clang;
+
+#[derive(Copy, PartialEq, Clone, Debug)]
+pub enum FieldAccessorKind {
+    None,
+    Regular,
+    Unsafe,
+    Immutable,
+}
+
+/// Annotations for a given item, or a field.
+#[derive(Clone, PartialEq, Debug)]
+pub struct Annotations {
+    /// Whether this item is marked as opaque. Only applies to types.
+    opaque: bool,
+    /// Whether this item should be hidden from the output. Only applies to
+    /// types.
+    hide: bool,
+    /// Whether this type should be replaced by another. The name must be the
+    /// canonical name that that type would get.
+    use_instead_of: Option<String>,
+    /// Manually disable deriving copy/clone on this type. Only applies to
+    /// struct or union types.
+    disallow_copy: bool,
+    /// Whether fields should be marked as private or not. You can set this on
+    /// structs (it will apply to all the fields), or individual fields.
+    private_fields: Option<bool>,
+    /// The kind of accessor this field will have. Also can be applied to
+    /// structs so all the fields inside share it by default.
+    accessor_kind: Option<FieldAccessorKind>,
+}
+
+fn parse_accessor(s: &str) -> FieldAccessorKind {
+    match s {
+        "false" => FieldAccessorKind::None,
+        "unsafe" => FieldAccessorKind::Unsafe,
+        "immutable" => FieldAccessorKind::Immutable,
+        _ => FieldAccessorKind::Regular,
+    }
+}
+
+impl Default for Annotations {
+    fn default() -> Self {
+        Annotations {
+            opaque: false,
+            hide: false,
+            use_instead_of: None,
+            disallow_copy: false,
+            private_fields: None,
+            accessor_kind: None
+        }
+    }
+}
+
+impl Annotations {
+    pub fn new(cursor: &clang::Cursor) -> Option<Annotations> {
+        let mut anno = Annotations::default();
+        let mut matched_one = false;
+        anno.parse(&cursor.comment(), &mut matched_one);
+
+        if matched_one {
+            Some(anno)
+        } else {
+            None
+        }
+    }
+
+    pub fn hide(&self) -> bool {
+        self.hide
+    }
+
+    pub fn opaque(&self) -> bool {
+        self.opaque
+    }
+
+    /// For a given type, indicates the type it should replace.
+    ///
+    /// For example, in the following code:
+    ///
+    /// ```cpp
+    ///
+    /// /** <div rustbindgen replaces="Bar"></div> */
+    /// struct Foo { int x; };
+    ///
+    /// struct Bar { char foo; };
+    /// ```
+    ///
+    /// the generated code would look something like:
+    ///
+    /// ```rust
+    /// /** <div rustbindgen replaces="Bar"></div> */
+    /// struct Bar {
+    ///     int x;
+    /// };
+    /// ```
+    ///
+    /// That is, code for `Foo` is used to generate `Bar`.
+    pub fn use_instead_of(&self) -> Option<&str> {
+        self.use_instead_of.as_ref().map(|s| &**s)
+    }
+
+    pub fn disallow_copy(&self) -> bool {
+        self.disallow_copy
+    }
+
+    pub fn private_fields(&self) -> Option<bool> {
+        self.private_fields
+    }
+
+    pub fn accessor_kind(&self) -> Option<FieldAccessorKind> {
+        self.accessor_kind
+    }
+
+    fn parse(&mut self, comment: &clang::Comment, matched: &mut bool) {
+        use clangll::CXComment_HTMLStartTag;
+        if comment.kind() == CXComment_HTMLStartTag &&
+           comment.get_tag_name() == "div" &&
+           comment.get_num_tag_attrs() > 1 &&
+           comment.get_tag_attr_name(0) == "rustbindgen" {
+            *matched = true;
+            for i in 0..comment.get_num_tag_attrs() {
+                let value = comment.get_tag_attr_value(i);
+                let name = comment.get_tag_attr_name(i);
+                match name.as_str() {
+                    "opaque" => self.opaque = true,
+                    "hide" => self.hide = true,
+                    "nocopy" => self.disallow_copy = true,
+                    "replaces" => self.use_instead_of = Some(value),
+                    "private" => self.private_fields = Some(value != "false"),
+                    "accessor"
+                        => self.accessor_kind = Some(parse_accessor(&value)),
+                    _ => {},
+                }
+            }
+        }
+
+        for i in 0..comment.num_children() {
+            self.parse(&comment.get_child(i), matched);
+        }
+    }
+}