5 files changed, 569 insertions, 0 deletions

diff --git a/src/grammar/items/consts.rs b/src/grammar/items/consts.rs
new file mode 100644
index 000000000..ca26a7814
--- /dev/null
+++ b/src/grammar/items/consts.rs
@@ -0,0 +1,20 @@
+use super::*;
+
+pub(super) fn static_item(p: &mut Parser) {
+    const_or_static(p, STATIC_KW)
+}
+
+pub(super) fn const_item(p: &mut Parser) {
+    const_or_static(p, CONST_KW)
+}
+
+fn const_or_static(p: &mut Parser, kw: SyntaxKind) {
+    assert!(p.at(kw));
+    p.bump();
+    p.eat(MUT_KW); // TODO: validator to forbid const mut
+    name(p);
+    types::ascription(p);
+    p.expect(EQ);
+    expressions::expr(p);
+    p.expect(SEMI);
+}
diff --git a/src/grammar/items/mod.rs b/src/grammar/items/mod.rs
new file mode 100644
index 000000000..d5f75f13d
--- /dev/null
+++ b/src/grammar/items/mod.rs
@@ -0,0 +1,290 @@
+use super::*;
+
+mod consts;
+mod structs;
+mod traits;
+mod use_item;
+
+pub(super) fn mod_contents(p: &mut Parser, stop_on_r_curly: bool) {
+    attributes::inner_attributes(p);
+    while !p.at(EOF) && !(stop_on_r_curly && p.at(R_CURLY)) {
+        item(p);
+    }
+}
+
+pub(super) const ITEM_FIRST: TokenSet =
+    token_set![EXTERN_KW, MOD_KW, USE_KW, STRUCT_KW, ENUM_KW, FN_KW, PUB_KW, POUND];
+
+pub(super) fn item(p: &mut Parser) {
+    let item = p.start();
+    attributes::outer_attributes(p);
+    visibility(p);
+    let la = p.nth(1);
+    let item_kind = match p.current() {
+        USE_KW => {
+            use_item::use_item(p);
+            USE_ITEM
+        }
+        // test extern_crate
+        // extern crate foo;
+        EXTERN_KW if la == CRATE_KW => {
+            extern_crate_item(p);
+            EXTERN_CRATE_ITEM
+        }
+        EXTERN_KW => {
+            abi(p);
+            match p.current() {
+                // test extern_fn
+                // extern fn foo() {}
+                FN_KW => {
+                    fn_item(p);
+                    FN_ITEM
+                }
+                // test extern_block
+                // extern {}
+                L_CURLY => {
+                    extern_block(p);
+                    EXTERN_BLOCK
+                }
+                // test extern_struct
+                // extern struct Foo;
+                _ => {
+                    item.abandon(p);
+                    p.error("expected `fn` or `{`");
+                    return;
+                }
+            }
+        }
+        STATIC_KW => {
+            consts::static_item(p);
+            STATIC_ITEM
+        }
+        CONST_KW => match p.nth(1) {
+            // test const_fn
+            // const fn foo() {}
+            FN_KW => {
+                p.bump();
+                fn_item(p);
+                FN_ITEM
+            }
+            // test const_unsafe_fn
+            // const unsafe fn foo() {}
+            UNSAFE_KW if p.nth(2) == FN_KW => {
+                p.bump();
+                p.bump();
+                fn_item(p);
+                FN_ITEM
+            }
+            _ => {
+                consts::const_item(p);
+                CONST_ITEM
+            }
+        },
+        UNSAFE_KW => {
+            p.bump();
+            let la = p.nth(1);
+            match p.current() {
+                // test unsafe_trait
+                // unsafe trait T {}
+                TRAIT_KW => {
+                    traits::trait_item(p);
+                    TRAIT_ITEM
+                }
+
+                // test unsafe_auto_trait
+                // unsafe auto trait T {}
+                IDENT if p.at_contextual_kw("auto") && la == TRAIT_KW => {
+                    p.bump_remap(AUTO_KW);
+                    traits::trait_item(p);
+                    TRAIT_ITEM
+                }
+
+                // test unsafe_impl
+                // unsafe impl Foo {}
+                IMPL_KW => {
+                    traits::impl_item(p);
+                    IMPL_ITEM
+                }
+
+                // test unsafe_default_impl
+                // unsafe default impl Foo {}
+                IDENT if p.at_contextual_kw("default") && la == IMPL_KW => {
+                    p.bump_remap(DEFAULT_KW);
+                    traits::impl_item(p);
+                    IMPL_ITEM
+                }
+
+                // test unsafe_extern_fn
+                // unsafe extern "C" fn foo() {}
+                EXTERN_KW => {
+                    abi(p);
+                    if !p.at(FN_KW) {
+                        item.abandon(p);
+                        p.error("expected function");
+                        return;
+                    }
+                    fn_item(p);
+                    FN_ITEM
+                }
+
+                // test unsafe_fn
+                // unsafe fn foo() {}
+                FN_KW => {
+                    fn_item(p);
+                    FN_ITEM
+                }
+
+                t => {
+                    item.abandon(p);
+                    let message = "expected `trait`, `impl` or `fn`";
+
+                    // test unsafe_block_in_mod
+                    // fn foo(){} unsafe { } fn bar(){}
+                    if t == L_CURLY {
+                        error_block(p, message);
+                    } else {
+                        p.error(message);
+                    }
+                    return;
+                }
+            }
+        }
+        TRAIT_KW => {
+            traits::trait_item(p);
+            TRAIT_ITEM
+        }
+        // test auto_trait
+        // auto trait T {}
+        IDENT if p.at_contextual_kw("auto") && la == TRAIT_KW => {
+            p.bump_remap(AUTO_KW);
+            traits::trait_item(p);
+            TRAIT_ITEM
+        }
+        IMPL_KW => {
+            traits::impl_item(p);
+            IMPL_ITEM
+        }
+        // test default_impl
+        // default impl Foo {}
+        IDENT if p.at_contextual_kw("default") && la == IMPL_KW => {
+            p.bump_remap(DEFAULT_KW);
+            traits::impl_item(p);
+            IMPL_ITEM
+        }
+
+        FN_KW => {
+            fn_item(p);
+            FN_ITEM
+        }
+        TYPE_KW => {
+            type_item(p);
+            TYPE_ITEM
+        }
+        MOD_KW => {
+            mod_item(p);
+            MOD_ITEM
+        }
+        STRUCT_KW => {
+            structs::struct_item(p);
+            STRUCT_ITEM
+        }
+        ENUM_KW => {
+            structs::enum_item(p);
+            ENUM_ITEM
+        }
+        L_CURLY => {
+            item.abandon(p);
+            error_block(p, "expected item");
+            return;
+        }
+        err_token => {
+            item.abandon(p);
+            let message = if err_token == SEMI {
+                //TODO: if the item is incomplete, this message is misleading
+                "expected item, found `;`\n\
+                 consider removing this semicolon"
+            } else {
+                "expected item"
+            };
+            p.err_and_bump(message);
+            return;
+        }
+    };
+    item.complete(p, item_kind);
+}
+
+fn extern_crate_item(p: &mut Parser) {
+    assert!(p.at(EXTERN_KW));
+    p.bump();
+    assert!(p.at(CRATE_KW));
+    p.bump();
+    name(p);
+    alias(p);
+    p.expect(SEMI);
+}
+
+fn extern_block(p: &mut Parser) {
+    assert!(p.at(L_CURLY));
+    p.bump();
+    p.expect(R_CURLY);
+}
+
+fn fn_item(p: &mut Parser) {
+    assert!(p.at(FN_KW));
+    p.bump();
+
+    name(p);
+    // test fn_item_type_params
+    // fn foo<T: Clone + Copy>(){}
+    type_params::type_param_list(p);
+
+    if p.at(L_PAREN) {
+        params::param_list(p);
+    } else {
+        p.error("expected function arguments");
+    }
+    // test fn_item_ret_type
+    // fn foo() {}
+    // fn bar() -> () {}
+    fn_ret_type(p);
+
+    // test fn_item_where_clause
+    // fn foo<T>() where T: Copy {}
+    type_params::where_clause(p);
+
+    expressions::block(p);
+}
+
+// test type_item
+// type Foo = Bar;
+fn type_item(p: &mut Parser) {
+    assert!(p.at(TYPE_KW));
+    p.bump();
+
+    name(p);
+
+    // test type_item_type_params
+    // type Result<T> = ();
+    type_params::type_param_list(p);
+
+    // test type_item_where_clause
+    // type Foo where Foo: Copy = ();
+    type_params::where_clause(p);
+
+    p.expect(EQ);
+    types::type_(p);
+    p.expect(SEMI);
+}
+
+fn mod_item(p: &mut Parser) {
+    assert!(p.at(MOD_KW));
+    p.bump();
+
+    name(p);
+    if !p.eat(SEMI) {
+        if p.expect(L_CURLY) {
+            mod_contents(p, true);
+            p.expect(R_CURLY);
+        }
+    }
+}
diff --git a/src/grammar/items/structs.rs b/src/grammar/items/structs.rs
new file mode 100644
index 000000000..7ced542a4
--- /dev/null
+++ b/src/grammar/items/structs.rs
@@ -0,0 +1,116 @@
+use super::*;
+
+pub(super) fn struct_item(p: &mut Parser) {
+    assert!(p.at(STRUCT_KW));
+    p.bump();
+
+    name(p);
+    type_params::type_param_list(p);
+    match p.current() {
+        WHERE_KW => {
+            type_params::where_clause(p);
+            match p.current() {
+                SEMI => {
+                    p.bump();
+                    return;
+                }
+                L_CURLY => named_fields(p),
+                _ => {
+                    //TODO: special case `(` error message
+                    p.error("expected `;` or `{`");
+                    return;
+                }
+            }
+        }
+        SEMI => {
+            p.bump();
+            return;
+        }
+        L_CURLY => named_fields(p),
+        L_PAREN => {
+            pos_fields(p);
+            p.expect(SEMI);
+        }
+        _ => {
+            p.error("expected `;`, `{`, or `(`");
+            return;
+        }
+    }
+}
+
+pub(super) fn enum_item(p: &mut Parser) {
+    assert!(p.at(ENUM_KW));
+    p.bump();
+    name(p);
+    type_params::type_param_list(p);
+    type_params::where_clause(p);
+    if p.expect(L_CURLY) {
+        while !p.at(EOF) && !p.at(R_CURLY) {
+            let var = p.start();
+            attributes::outer_attributes(p);
+            if p.at(IDENT) {
+                p.bump();
+                match p.current() {
+                    L_CURLY => named_fields(p),
+                    L_PAREN => pos_fields(p),
+                    EQ => {
+                        p.bump();
+                        expressions::expr(p);
+                    }
+                    _ => (),
+                }
+                var.complete(p, ENUM_VARIANT);
+            } else {
+                var.abandon(p);
+                p.err_and_bump("expected enum variant");
+            }
+            if !p.at(R_CURLY) {
+                p.expect(COMMA);
+            }
+        }
+        p.expect(R_CURLY);
+    }
+}
+
+fn named_fields(p: &mut Parser) {
+    assert!(p.at(L_CURLY));
+    p.bump();
+    while !p.at(R_CURLY) && !p.at(EOF) {
+        named_field(p);
+        if !p.at(R_CURLY) {
+            p.expect(COMMA);
+        }
+    }
+    p.expect(R_CURLY);
+
+    fn named_field(p: &mut Parser) {
+        let field = p.start();
+        visibility(p);
+        if p.at(IDENT) {
+            name(p);
+            p.expect(COLON);
+            types::type_(p);
+            field.complete(p, NAMED_FIELD);
+        } else {
+            field.abandon(p);
+            p.err_and_bump("expected field declaration");
+        }
+    }
+}
+
+fn pos_fields(p: &mut Parser) {
+    if !p.expect(L_PAREN) {
+        return;
+    }
+    while !p.at(R_PAREN) && !p.at(EOF) {
+        let pos_field = p.start();
+        visibility(p);
+        types::type_(p);
+        pos_field.complete(p, POS_FIELD);
+
+        if !p.at(R_PAREN) {
+            p.expect(COMMA);
+        }
+    }
+    p.expect(R_PAREN);
+}
diff --git a/src/grammar/items/traits.rs b/src/grammar/items/traits.rs
new file mode 100644
index 000000000..bda13e565
--- /dev/null
+++ b/src/grammar/items/traits.rs
@@ -0,0 +1,77 @@
+use super::*;
+
+// test trait_item
+// trait T<U>: Hash + Clone where U: Copy {}
+pub(super) fn trait_item(p: &mut Parser) {
+    assert!(p.at(TRAIT_KW));
+    p.bump();
+    name(p);
+    type_params::type_param_list(p);
+    if p.at(COLON) {
+        type_params::bounds(p);
+    }
+    type_params::where_clause(p);
+    p.expect(L_CURLY);
+    p.expect(R_CURLY);
+}
+
+// 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::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::where_clause(p);
+    p.expect(L_CURLY);
+
+    // test impl_item_items
+    // impl F {
+    //     type A = i32;
+    //     const B: i32 = 92;
+    //     fn foo() {}
+    //     fn bar(&self) {}
+    // }
+    while !p.at(EOF) && !p.at(R_CURLY) {
+        item(p);
+    }
+    p.expect(R_CURLY);
+}
+
+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)
+}
diff --git a/src/grammar/items/use_item.rs b/src/grammar/items/use_item.rs
new file mode 100644
index 000000000..a3f7f0da8
--- /dev/null
+++ b/src/grammar/items/use_item.rs
@@ -0,0 +1,66 @@
+use super::*;
+
+pub(super) fn use_item(p: &mut Parser) {
+    assert!(p.at(USE_KW));
+    p.bump();
+    use_tree(p);
+    p.expect(SEMI);
+}
+
+fn use_tree(p: &mut Parser) {
+    let la = p.nth(1);
+    let m = p.start();
+    match (p.current(), la) {
+        (STAR, _) => p.bump(),
+        (COLONCOLON, STAR) => {
+            p.bump();
+            p.bump();
+        }
+        (L_CURLY, _) | (COLONCOLON, L_CURLY) => {
+            if p.at(COLONCOLON) {
+                p.bump();
+            }
+            nested_trees(p);
+        }
+        _ if paths::is_path_start(p) => {
+            paths::use_path(p);
+            match p.current() {
+                AS_KW => {
+                    alias(p);
+                }
+                COLONCOLON => {
+                    p.bump();
+                    match p.current() {
+                        STAR => {
+                            p.bump();
+                        }
+                        L_CURLY => nested_trees(p),
+                        _ => {
+                            // is this unreachable?
+                            p.error("expected `{` or `*`");
+                        }
+                    }
+                }
+                _ => (),
+            }
+        }
+        _ => {
+            m.abandon(p);
+            p.err_and_bump("expected one of `*`, `::`, `{`, `self`, `super`, `indent`");
+            return;
+        }
+    }
+    m.complete(p, USE_TREE);
+}
+
+fn nested_trees(p: &mut Parser) {
+    assert!(p.at(L_CURLY));
+    p.bump();
+    while !p.at(EOF) && !p.at(R_CURLY) {
+        use_tree(p);
+        if !p.at(R_CURLY) {
+            p.expect(COMMA);
+        }
+    }
+    p.expect(R_CURLY);
+}