1 files changed, 361 insertions, 0 deletions

diff --git a/crates/hir_expand/src/builtin_derive.rs b/crates/hir_expand/src/builtin_derive.rs
new file mode 100644
index 000000000..988a60d56
--- /dev/null
+++ b/crates/hir_expand/src/builtin_derive.rs
@@ -0,0 +1,361 @@
+//! Builtin derives.
+
+use log::debug;
+
+use parser::FragmentKind;
+use syntax::{
+    ast::{self, AstNode, GenericParamsOwner, ModuleItemOwner, NameOwner},
+    match_ast,
+};
+
+use crate::{db::AstDatabase, name, quote, LazyMacroId, MacroDefId, MacroDefKind};
+
+macro_rules! register_builtin {
+    ( $($trait:ident => $expand:ident),* ) => {
+        #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+        pub enum BuiltinDeriveExpander {
+            $($trait),*
+        }
+
+        impl BuiltinDeriveExpander {
+            pub fn expand(
+                &self,
+                db: &dyn AstDatabase,
+                id: LazyMacroId,
+                tt: &tt::Subtree,
+            ) -> Result<tt::Subtree, mbe::ExpandError> {
+                let expander = match *self {
+                    $( BuiltinDeriveExpander::$trait => $expand, )*
+                };
+                expander(db, id, tt)
+            }
+        }
+
+        pub fn find_builtin_derive(ident: &name::Name) -> Option<MacroDefId> {
+            let kind = match ident {
+                $( id if id == &name::name![$trait] => BuiltinDeriveExpander::$trait, )*
+                 _ => return None,
+            };
+
+            Some(MacroDefId { krate: None, ast_id: None, kind: MacroDefKind::BuiltInDerive(kind), local_inner: false })
+        }
+    };
+}
+
+register_builtin! {
+    Copy => copy_expand,
+    Clone => clone_expand,
+    Default => default_expand,
+    Debug => debug_expand,
+    Hash => hash_expand,
+    Ord => ord_expand,
+    PartialOrd => partial_ord_expand,
+    Eq => eq_expand,
+    PartialEq => partial_eq_expand
+}
+
+struct BasicAdtInfo {
+    name: tt::Ident,
+    type_params: usize,
+}
+
+fn parse_adt(tt: &tt::Subtree) -> Result<BasicAdtInfo, mbe::ExpandError> {
+    let (parsed, token_map) = mbe::token_tree_to_syntax_node(tt, FragmentKind::Items)?; // FragmentKind::Items doesn't parse attrs?
+    let macro_items = ast::MacroItems::cast(parsed.syntax_node()).ok_or_else(|| {
+        debug!("derive node didn't parse");
+        mbe::ExpandError::UnexpectedToken
+    })?;
+    let item = macro_items.items().next().ok_or_else(|| {
+        debug!("no module item parsed");
+        mbe::ExpandError::NoMatchingRule
+    })?;
+    let node = item.syntax();
+    let (name, params) = match_ast! {
+        match node {
+            ast::Struct(it) => (it.name(), it.generic_param_list()),
+            ast::Enum(it) => (it.name(), it.generic_param_list()),
+            ast::Union(it) => (it.name(), it.generic_param_list()),
+            _ => {
+                debug!("unexpected node is {:?}", node);
+                return Err(mbe::ExpandError::ConversionError)
+            },
+        }
+    };
+    let name = name.ok_or_else(|| {
+        debug!("parsed item has no name");
+        mbe::ExpandError::NoMatchingRule
+    })?;
+    let name_token_id = token_map.token_by_range(name.syntax().text_range()).ok_or_else(|| {
+        debug!("name token not found");
+        mbe::ExpandError::ConversionError
+    })?;
+    let name_token = tt::Ident { id: name_token_id, text: name.text().clone() };
+    let type_params = params.map_or(0, |type_param_list| type_param_list.type_params().count());
+    Ok(BasicAdtInfo { name: name_token, type_params })
+}
+
+fn make_type_args(n: usize, bound: Vec<tt::TokenTree>) -> Vec<tt::TokenTree> {
+    let mut result = Vec::<tt::TokenTree>::new();
+    result.push(
+        tt::Leaf::Punct(tt::Punct {
+            char: '<',
+            spacing: tt::Spacing::Alone,
+            id: tt::TokenId::unspecified(),
+        })
+        .into(),
+    );
+    for i in 0..n {
+        if i > 0 {
+            result.push(
+                tt::Leaf::Punct(tt::Punct {
+                    char: ',',
+                    spacing: tt::Spacing::Alone,
+                    id: tt::TokenId::unspecified(),
+                })
+                .into(),
+            );
+        }
+        result.push(
+            tt::Leaf::Ident(tt::Ident {
+                id: tt::TokenId::unspecified(),
+                text: format!("T{}", i).into(),
+            })
+            .into(),
+        );
+        result.extend(bound.iter().cloned());
+    }
+    result.push(
+        tt::Leaf::Punct(tt::Punct {
+            char: '>',
+            spacing: tt::Spacing::Alone,
+            id: tt::TokenId::unspecified(),
+        })
+        .into(),
+    );
+    result
+}
+
+fn expand_simple_derive(
+    tt: &tt::Subtree,
+    trait_path: tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let info = parse_adt(tt)?;
+    let name = info.name;
+    let trait_path_clone = trait_path.token_trees.clone();
+    let bound = (quote! { : ##trait_path_clone }).token_trees;
+    let type_params = make_type_args(info.type_params, bound);
+    let type_args = make_type_args(info.type_params, Vec::new());
+    let trait_path = trait_path.token_trees;
+    let expanded = quote! {
+        impl ##type_params ##trait_path for #name ##type_args {}
+    };
+    Ok(expanded)
+}
+
+fn find_builtin_crate(db: &dyn AstDatabase, id: LazyMacroId) -> tt::TokenTree {
+    // FIXME: make hygiene works for builtin derive macro
+    // such that $crate can be used here.
+    let cg = db.crate_graph();
+    let krate = db.lookup_intern_macro(id).krate;
+
+    // XXX
+    //  All crates except core itself should have a dependency on core,
+    //  We detect `core` by seeing whether it doesn't have such a dependency.
+    let tt = if cg[krate].dependencies.iter().any(|dep| &*dep.name == "core") {
+        quote! { core }
+    } else {
+        quote! { crate }
+    };
+
+    tt.token_trees[0].clone()
+}
+
+fn copy_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let krate = find_builtin_crate(db, id);
+    expand_simple_derive(tt, quote! { #krate::marker::Copy })
+}
+
+fn clone_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let krate = find_builtin_crate(db, id);
+    expand_simple_derive(tt, quote! { #krate::clone::Clone })
+}
+
+fn default_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let krate = find_builtin_crate(db, id);
+    expand_simple_derive(tt, quote! { #krate::default::Default })
+}
+
+fn debug_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let krate = find_builtin_crate(db, id);
+    expand_simple_derive(tt, quote! { #krate::fmt::Debug })
+}
+
+fn hash_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let krate = find_builtin_crate(db, id);
+    expand_simple_derive(tt, quote! { #krate::hash::Hash })
+}
+
+fn eq_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let krate = find_builtin_crate(db, id);
+    expand_simple_derive(tt, quote! { #krate::cmp::Eq })
+}
+
+fn partial_eq_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let krate = find_builtin_crate(db, id);
+    expand_simple_derive(tt, quote! { #krate::cmp::PartialEq })
+}
+
+fn ord_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let krate = find_builtin_crate(db, id);
+    expand_simple_derive(tt, quote! { #krate::cmp::Ord })
+}
+
+fn partial_ord_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> Result<tt::Subtree, mbe::ExpandError> {
+    let krate = find_builtin_crate(db, id);
+    expand_simple_derive(tt, quote! { #krate::cmp::PartialOrd })
+}
+
+#[cfg(test)]
+mod tests {
+    use base_db::{fixture::WithFixture, CrateId, SourceDatabase};
+    use name::{known, Name};
+
+    use crate::{test_db::TestDB, AstId, MacroCallId, MacroCallKind, MacroCallLoc};
+
+    use super::*;
+
+    fn expand_builtin_derive(s: &str, name: Name) -> String {
+        let def = find_builtin_derive(&name).unwrap();
+        let fixture = format!(
+            r#"//- /main.rs crate:main deps:core
+<|>
+{}
+//- /lib.rs crate:core
+// empty
+"#,
+            s
+        );
+
+        let (db, file_pos) = TestDB::with_position(&fixture);
+        let file_id = file_pos.file_id;
+        let parsed = db.parse(file_id);
+        let items: Vec<_> =
+            parsed.syntax_node().descendants().filter_map(ast::Item::cast).collect();
+
+        let ast_id_map = db.ast_id_map(file_id.into());
+
+        let attr_id = AstId::new(file_id.into(), ast_id_map.ast_id(&items[0]));
+
+        let loc = MacroCallLoc {
+            def,
+            krate: CrateId(0),
+            kind: MacroCallKind::Attr(attr_id, name.to_string()),
+        };
+
+        let id: MacroCallId = db.intern_macro(loc).into();
+        let parsed = db.parse_or_expand(id.as_file()).unwrap();
+
+        // FIXME text() for syntax nodes parsed from token tree looks weird
+        // because there's no whitespace, see below
+        parsed.text().to_string()
+    }
+
+    #[test]
+    fn test_copy_expand_simple() {
+        let expanded = expand_builtin_derive(
+            r#"
+        #[derive(Copy)]
+        struct Foo;
+"#,
+            known::Copy,
+        );
+
+        assert_eq!(expanded, "impl< >core::marker::CopyforFoo< >{}");
+    }
+
+    #[test]
+    fn test_copy_expand_with_type_params() {
+        let expanded = expand_builtin_derive(
+            r#"
+        #[derive(Copy)]
+        struct Foo<A, B>;
+"#,
+            known::Copy,
+        );
+
+        assert_eq!(
+            expanded,
+            "impl<T0:core::marker::Copy,T1:core::marker::Copy>core::marker::CopyforFoo<T0,T1>{}"
+        );
+    }
+
+    #[test]
+    fn test_copy_expand_with_lifetimes() {
+        let expanded = expand_builtin_derive(
+            r#"
+        #[derive(Copy)]
+        struct Foo<A, B, 'a, 'b>;
+"#,
+            known::Copy,
+        );
+
+        // We currently just ignore lifetimes
+
+        assert_eq!(
+            expanded,
+            "impl<T0:core::marker::Copy,T1:core::marker::Copy>core::marker::CopyforFoo<T0,T1>{}"
+        );
+    }
+
+    #[test]
+    fn test_clone_expand() {
+        let expanded = expand_builtin_derive(
+            r#"
+        #[derive(Clone)]
+        struct Foo<A, B>;
+"#,
+            known::Clone,
+        );
+
+        assert_eq!(
+            expanded,
+            "impl<T0:core::clone::Clone,T1:core::clone::Clone>core::clone::CloneforFoo<T0,T1>{}"
+        );
+    }
+}