DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Mercurial (cdf352f02ac4)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342
//! Template declaration and instantiation related things.
//!
//! The nomenclature surrounding templates is often confusing, so here are a few
//! brief definitions:
//!
//! * "Template definition": a class/struct/alias/function definition that takes
//! generic template parameters. For example:
//!
//! ```c++
//! template<typename T>
//! class List<T> {
//!     // ...
//! };
//! ```
//!
//! * "Template instantiation": an instantiation is a use of a template with
//! concrete template arguments. For example, `List<int>`.
//!
//! * "Template specialization": an alternative template definition providing a
//! custom definition for instantiations with the matching template
//! arguments. This C++ feature is unsupported by bindgen. For example:
//!
//! ```c++
//! template<>
//! class List<int> {
//!     // Special layout for int lists...
//! };
//! ```

use super::context::{BindgenContext, ItemId, TypeId};
use super::item::{IsOpaque, Item, ItemAncestors, ItemCanonicalPath};
use super::traversal::{EdgeKind, Trace, Tracer};
use clang;
use parse::ClangItemParser;

/// Template declaration (and such declaration's template parameters) related
/// methods.
///
/// This trait's methods distinguish between `None` and `Some([])` for
/// declarations that are not templates and template declarations with zero
/// parameters, in general.
///
/// Consider this example:
///
/// ```c++
/// template <typename T, typename U>
/// class Foo {
///     T use_of_t;
///     U use_of_u;
///
///     template <typename V>
///     using Bar = V*;
///
///     class Inner {
///         T        x;
///         U        y;
///         Bar<int> z;
///     };
///
///     template <typename W>
///     class Lol {
///         // No use of W, but here's a use of T.
///         T t;
///     };
///
///     template <typename X>
///     class Wtf {
///         // X is not used because W is not used.
///         Lol<X> lololol;
///     };
/// };
///
/// class Qux {
///     int y;
/// };
/// ```
///
/// The following table depicts the results of each trait method when invoked on
/// each of the declarations above:
///
/// +------+----------------------+--------------------------+------------------------+----
/// |Decl. | self_template_params | num_self_template_params | all_template_parameters| ...
/// +------+----------------------+--------------------------+------------------------+----
/// |Foo   | [T, U]               | 2                        | [T, U]                 | ...
/// |Bar   | [V]                  | 1                        | [T, U, V]              | ...
/// |Inner | []                   | 0                        | [T, U]                 | ...
/// |Lol   | [W]                  | 1                        | [T, U, W]              | ...
/// |Wtf   | [X]                  | 1                        | [T, U, X]              | ...
/// |Qux   | []                   | 0                        | []                     | ...
/// +------+----------------------+--------------------------+------------------------+----
///
/// ----+------+-----+----------------------+
/// ... |Decl. | ... | used_template_params |
/// ----+------+-----+----------------------+
/// ... |Foo   | ... | [T, U]               |
/// ... |Bar   | ... | [V]                  |
/// ... |Inner | ... | []                   |
/// ... |Lol   | ... | [T]                  |
/// ... |Wtf   | ... | [T]                  |
/// ... |Qux   | ... | []                   |
/// ----+------+-----+----------------------+
pub trait TemplateParameters: Sized {
    /// Get the set of `ItemId`s that make up this template declaration's free
    /// template parameters.
    ///
    /// Note that these might *not* all be named types: C++ allows
    /// constant-value template parameters as well as template-template
    /// parameters. Of course, Rust does not allow generic parameters to be
    /// anything but types, so we must treat them as opaque, and avoid
    /// instantiating them.
    fn self_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId>;

    /// Get the number of free template parameters this template declaration
    /// has.
    fn num_self_template_params(&self, ctx: &BindgenContext) -> usize {
        self.self_template_params(ctx).len()
    }

    /// Get the complete set of template parameters that can affect this
    /// declaration.
    ///
    /// Note that this item doesn't need to be a template declaration itself for
    /// `Some` to be returned here (in contrast to `self_template_params`). If
    /// this item is a member of a template declaration, then the parent's
    /// template parameters are included here.
    ///
    /// In the example above, `Inner` depends on both of the `T` and `U` type
    /// parameters, even though it is not itself a template declaration and
    /// therefore has no type parameters itself. Perhaps it helps to think about
    /// how we would fully reference such a member type in C++:
    /// `Foo<int,char>::Inner`. `Foo` *must* be instantiated with template
    /// arguments before we can gain access to the `Inner` member type.
    fn all_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId>
    where
        Self: ItemAncestors,
    {
        let ancestors: Vec<_> = self.ancestors(ctx).collect();
        ancestors
            .into_iter()
            .rev()
            .flat_map(|id| id.self_template_params(ctx).into_iter())
            .collect()
    }

    /// Get only the set of template parameters that this item uses. This is a
    /// subset of `all_template_params` and does not necessarily contain any of
    /// `self_template_params`.
    fn used_template_params(&self, ctx: &BindgenContext) -> Vec<TypeId>
    where
        Self: AsRef<ItemId>,
    {
        assert!(
            ctx.in_codegen_phase(),
            "template parameter usage is not computed until codegen"
        );

        let id = *self.as_ref();
        ctx.resolve_item(id)
            .all_template_params(ctx)
            .into_iter()
            .filter(|p| ctx.uses_template_parameter(id, *p))
            .collect()
    }
}

/// A trait for things which may or may not be a named template type parameter.
pub trait AsTemplateParam {
    /// Any extra information the implementor might need to make this decision.
    type Extra;

    /// Convert this thing to the item id of a named template type parameter.
    fn as_template_param(
        &self,
        ctx: &BindgenContext,
        extra: &Self::Extra,
    ) -> Option<TypeId>;

    /// Is this a named template type parameter?
    fn is_template_param(
        &self,
        ctx: &BindgenContext,
        extra: &Self::Extra,
    ) -> bool {
        self.as_template_param(ctx, extra).is_some()
    }
}

/// A concrete instantiation of a generic template.
#[derive(Clone, Debug)]
pub struct TemplateInstantiation {
    /// The template definition which this is instantiating.
    definition: TypeId,
    /// The concrete template arguments, which will be substituted in the
    /// definition for the generic template parameters.
    args: Vec<TypeId>,
}

impl TemplateInstantiation {
    /// Construct a new template instantiation from the given parts.
    pub fn new<I>(definition: TypeId, args: I) -> TemplateInstantiation
    where
        I: IntoIterator<Item = TypeId>,
    {
        TemplateInstantiation {
            definition,
            args: args.into_iter().collect(),
        }
    }

    /// Get the template definition for this instantiation.
    pub fn template_definition(&self) -> TypeId {
        self.definition
    }

    /// Get the concrete template arguments used in this instantiation.
    pub fn template_arguments(&self) -> &[TypeId] {
        &self.args[..]
    }

    /// Parse a `TemplateInstantiation` from a clang `Type`.
    pub fn from_ty(
        ty: &clang::Type,
        ctx: &mut BindgenContext,
    ) -> Option<TemplateInstantiation> {
        use clang_sys::*;

        let template_args = ty.template_args().map_or(vec![], |args| match ty
            .canonical_type()
            .template_args()
        {
            Some(canonical_args) => {
                let arg_count = args.len();
                args.chain(canonical_args.skip(arg_count))
                    .filter(|t| t.kind() != CXType_Invalid)
                    .map(|t| {
                        Item::from_ty_or_ref(t, t.declaration(), None, ctx)
                    })
                    .collect()
            }
            None => args
                .filter(|t| t.kind() != CXType_Invalid)
                .map(|t| Item::from_ty_or_ref(t, t.declaration(), None, ctx))
                .collect(),
        });

        let declaration = ty.declaration();
        let definition = if declaration.kind() == CXCursor_TypeAliasTemplateDecl
        {
            Some(declaration)
        } else {
            declaration.specialized().or_else(|| {
                let mut template_ref = None;
                ty.declaration().visit(|child| {
                    if child.kind() == CXCursor_TemplateRef {
                        template_ref = Some(child);
                        return CXVisit_Break;
                    }

                    // Instantiations of template aliases might have the
                    // TemplateRef to the template alias definition arbitrarily
                    // deep, so we need to recurse here and not only visit
                    // direct children.
                    CXChildVisit_Recurse
                });

                template_ref.and_then(|cur| cur.referenced())
            })
        };

        let definition = match definition {
            Some(def) => def,
            None => {
                if !ty.declaration().is_builtin() {
                    warn!(
                        "Could not find template definition for template \
                         instantiation"
                    );
                }
                return None;
            }
        };

        let template_definition =
            Item::from_ty_or_ref(definition.cur_type(), definition, None, ctx);

        Some(TemplateInstantiation::new(
            template_definition,
            template_args,
        ))
    }
}

impl IsOpaque for TemplateInstantiation {
    type Extra = Item;

    /// Is this an opaque template instantiation?
    fn is_opaque(&self, ctx: &BindgenContext, item: &Item) -> bool {
        if self.template_definition().is_opaque(ctx, &()) {
            return true;
        }

        // TODO(#774): This doesn't properly handle opaque instantiations where
        // an argument is itself an instantiation because `canonical_name` does
        // not insert the template arguments into the name, ie it for nested
        // template arguments it creates "Foo" instead of "Foo<int>". The fully
        // correct fix is to make `canonical_{name,path}` include template
        // arguments properly.

        let mut path = item.canonical_path(ctx);
        let args: Vec<_> = self
            .template_arguments()
            .iter()
            .map(|arg| {
                let arg_path = arg.canonical_path(ctx);
                arg_path[1..].join("::")
            })
            .collect();
        {
            let last = path.last_mut().unwrap();
            last.push('<');
            last.push_str(&args.join(", "));
            last.push('>');
        }

        ctx.opaque_by_name(&path)
    }
}

impl Trace for TemplateInstantiation {
    type Extra = ();

    fn trace<T>(&self, _ctx: &BindgenContext, tracer: &mut T, _: &())
    where
        T: Tracer,
    {
        tracer
            .visit_kind(self.definition.into(), EdgeKind::TemplateDeclaration);
        for arg in self.template_arguments() {
            tracer.visit_kind(arg.into(), EdgeKind::TemplateArgument);
        }
    }
}