1 files changed, 117 insertions, 0 deletions

diff --git a/crates/ra_syntax/src/grammar/items/traits.rs b/crates/ra_syntax/src/grammar/items/traits.rs
new file mode 100644
index 000000000..c21cfb1a9
--- /dev/null
+++ b/crates/ra_syntax/src/grammar/items/traits.rs
@@ -0,0 +1,117 @@
+use super::*;
+
+// test trait_item
+// trait T<U>: Hash + Clone where U: Copy {}
+pub(super) fn trait_def(p: &mut Parser) {
+    assert!(p.at(TRAIT_KW));
+    p.bump();
+    name_r(p, ITEM_RECOVERY_SET);
+    type_params::opt_type_param_list(p);
+    if p.at(COLON) {
+        type_params::bounds(p);
+    }
+    type_params::opt_where_clause(p);
+    if p.at(L_CURLY) {
+        trait_item_list(p);
+    } else {
+        p.error("expected `{`");
+    }
+}
+
+// test trait_item_list
+// impl F {
+//     type A: Clone;
+//     const B: i32;
+//     fn foo() {}
+//     fn bar(&self);
+// }
+pub(crate) fn trait_item_list(p: &mut Parser) {
+    assert!(p.at(L_CURLY));
+    let m = p.start();
+    p.bump();
+    while !p.at(EOF) && !p.at(R_CURLY) {
+        if p.at(L_CURLY) {
+            error_block(p, "expected an item");
+            continue;
+        }
+        item_or_macro(p, true, ItemFlavor::Trait);
+    }
+    p.expect(R_CURLY);
+    m.complete(p, ITEM_LIST);
+}
+
+// test impl_item
+// impl Foo {}
+pub(super) fn impl_item(p: &mut Parser) {
+    assert!(p.at(IMPL_KW));
+    p.bump();
+    if choose_type_params_over_qpath(p) {
+        type_params::opt_type_param_list(p);
+    }
+
+    // TODO: never type
+    // impl ! {}
+
+    // test impl_item_neg
+    // impl !Send for X {}
+    p.eat(EXCL);
+    types::type_(p);
+    if p.eat(FOR_KW) {
+        types::type_(p);
+    }
+    type_params::opt_where_clause(p);
+    if p.at(L_CURLY) {
+        impl_item_list(p);
+    } else {
+        p.error("expected `{`");
+    }
+}
+
+// test impl_item_list
+// impl F {
+//     type A = i32;
+//     const B: i32 = 92;
+//     fn foo() {}
+//     fn bar(&self) {}
+// }
+pub(crate) fn impl_item_list(p: &mut Parser) {
+    assert!(p.at(L_CURLY));
+    let m = p.start();
+    p.bump();
+
+    while !p.at(EOF) && !p.at(R_CURLY) {
+        if p.at(L_CURLY) {
+            error_block(p, "expected an item");
+            continue;
+        }
+        item_or_macro(p, true, ItemFlavor::Mod);
+    }
+    p.expect(R_CURLY);
+    m.complete(p, ITEM_LIST);
+}
+
+fn choose_type_params_over_qpath(p: &Parser) -> bool {
+    // There's an ambiguity between generic parameters and qualified paths in impls.
+    // If we see `<` it may start both, so we have to inspect some following tokens.
+    // The following combinations can only start generics,
+    // but not qualified paths (with one exception):
+    //     `<` `>` - empty generic parameters
+    //     `<` `#` - generic parameters with attributes
+    //     `<` (LIFETIME|IDENT) `>` - single generic parameter
+    //     `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
+    //     `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
+    //     `<` (LIFETIME|IDENT) `=` - generic parameter with a default
+    // The only truly ambiguous case is
+    //     `<` IDENT `>` `::` IDENT ...
+    // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
+    // because this is what almost always expected in practice, qualified paths in impls
+    // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
+    if !p.at(L_ANGLE) {
+        return false;
+    }
+    if p.nth(1) == POUND || p.nth(1) == R_ANGLE {
+        return true;
+    }
+    (p.nth(1) == LIFETIME || p.nth(1) == IDENT)
+        && (p.nth(2) == R_ANGLE || p.nth(2) == COMMA || p.nth(2) == COLON || p.nth(2) == EQ)
+}