1 files changed, 432 insertions, 0 deletions

diff --git a/crates/parser/src/grammar/items.rs b/crates/parser/src/grammar/items.rs
new file mode 100644
index 000000000..d091b0fbb
--- /dev/null
+++ b/crates/parser/src/grammar/items.rs
@@ -0,0 +1,432 @@
+//! FIXME: write short doc here
+
+mod consts;
+mod adt;
+mod traits;
+mod use_item;
+
+pub(crate) use self::{
+    adt::{enum_variant_list, record_field_def_list},
+    expressions::{match_arm_list, record_field_list},
+    traits::{impl_item_list, trait_item_list},
+    use_item::use_tree_list,
+};
+use super::*;
+
+// test mod_contents
+// fn foo() {}
+// macro_rules! foo {}
+// foo::bar!();
+// super::baz! {}
+// struct S;
+pub(super) fn mod_contents(p: &mut Parser, stop_on_r_curly: bool) {
+    attributes::inner_attributes(p);
+    while !(stop_on_r_curly && p.at(T!['}']) || p.at(EOF)) {
+        item_or_macro(p, stop_on_r_curly)
+    }
+}
+
+pub(super) const ITEM_RECOVERY_SET: TokenSet = token_set![
+    FN_KW, STRUCT_KW, ENUM_KW, IMPL_KW, TRAIT_KW, CONST_KW, STATIC_KW, LET_KW, MOD_KW, PUB_KW,
+    CRATE_KW, USE_KW, MACRO_KW
+];
+
+pub(super) fn item_or_macro(p: &mut Parser, stop_on_r_curly: bool) {
+    let m = p.start();
+    attributes::outer_attributes(p);
+    let m = match maybe_item(p, m) {
+        Ok(()) => {
+            if p.at(T![;]) {
+                p.err_and_bump(
+                    "expected item, found `;`\n\
+                     consider removing this semicolon",
+                );
+            }
+            return;
+        }
+        Err(m) => m,
+    };
+    if paths::is_use_path_start(p) {
+        match macro_call(p) {
+            BlockLike::Block => (),
+            BlockLike::NotBlock => {
+                p.expect(T![;]);
+            }
+        }
+        m.complete(p, MACRO_CALL);
+    } else {
+        m.abandon(p);
+        if p.at(T!['{']) {
+            error_block(p, "expected an item");
+        } else if p.at(T!['}']) && !stop_on_r_curly {
+            let e = p.start();
+            p.error("unmatched `}`");
+            p.bump(T!['}']);
+            e.complete(p, ERROR);
+        } else if !p.at(EOF) && !p.at(T!['}']) {
+            p.err_and_bump("expected an item");
+        } else {
+            p.error("expected an item");
+        }
+    }
+}
+
+pub(super) fn maybe_item(p: &mut Parser, m: Marker) -> Result<(), Marker> {
+    // test_err pub_expr
+    // fn foo() { pub 92; }
+    let has_visibility = opt_visibility(p);
+
+    let m = match items_without_modifiers(p, m) {
+        Ok(()) => return Ok(()),
+        Err(m) => m,
+    };
+
+    let mut has_mods = false;
+
+    // modifiers
+    has_mods |= p.eat(T![const]);
+
+    // test_err async_without_semicolon
+    // fn foo() { let _ = async {} }
+    if p.at(T![async]) && p.nth(1) != T!['{'] && p.nth(1) != T![move] && p.nth(1) != T![|] {
+        p.eat(T![async]);
+        has_mods = true;
+    }
+
+    // test_err unsafe_block_in_mod
+    // fn foo(){} unsafe { } fn bar(){}
+    if p.at(T![unsafe]) && p.nth(1) != T!['{'] {
+        p.eat(T![unsafe]);
+        has_mods = true;
+    }
+
+    if p.at(T![extern]) {
+        has_mods = true;
+        abi(p);
+    }
+    if p.at(IDENT) && p.at_contextual_kw("auto") && p.nth(1) == T![trait] {
+        p.bump_remap(T![auto]);
+        has_mods = true;
+    }
+
+    // test default_item
+    // default impl T for Foo {}
+    if p.at(IDENT) && p.at_contextual_kw("default") {
+        match p.nth(1) {
+            T![fn] | T![type] | T![const] | T![impl] => {
+                p.bump_remap(T![default]);
+                has_mods = true;
+            }
+            T![unsafe] => {
+                // test default_unsafe_item
+                // default unsafe impl T for Foo {
+                //     default unsafe fn foo() {}
+                // }
+                if matches!(p.nth(2), T![impl] | T![fn]) {
+                    p.bump_remap(T![default]);
+                    p.bump(T![unsafe]);
+                    has_mods = true;
+                }
+            }
+            _ => (),
+        }
+    }
+
+    // test existential_type
+    // existential type Foo: Fn() -> usize;
+    if p.at(IDENT) && p.at_contextual_kw("existential") && p.nth(1) == T![type] {
+        p.bump_remap(T![existential]);
+        has_mods = true;
+    }
+
+    // items
+    match p.current() {
+        // test fn
+        // fn foo() {}
+        T![fn] => {
+            fn_def(p);
+            m.complete(p, FN);
+        }
+
+        // test trait
+        // trait T {}
+        T![trait] => {
+            traits::trait_def(p);
+            m.complete(p, TRAIT);
+        }
+
+        T![const] => {
+            consts::const_def(p, m);
+        }
+
+        // test impl
+        // impl T for S {}
+        T![impl] => {
+            traits::impl_def(p);
+            m.complete(p, IMPL);
+        }
+
+        T![type] => {
+            type_def(p, m);
+        }
+        _ => {
+            if !has_visibility && !has_mods {
+                return Err(m);
+            } else {
+                if has_mods {
+                    p.error("expected existential, fn, trait or impl");
+                } else {
+                    p.error("expected an item");
+                }
+                m.complete(p, ERROR);
+            }
+        }
+    }
+    Ok(())
+}
+
+fn items_without_modifiers(p: &mut Parser, m: Marker) -> Result<(), Marker> {
+    let la = p.nth(1);
+    match p.current() {
+        // test extern_crate
+        // extern crate foo;
+        T![extern] if la == T![crate] => extern_crate_item(p, m),
+        T![type] => {
+            type_def(p, m);
+        }
+        T![mod] => mod_item(p, m),
+        T![struct] => {
+            // test struct_items
+            // struct Foo;
+            // struct Foo {}
+            // struct Foo();
+            // struct Foo(String, usize);
+            // struct Foo {
+            //     a: i32,
+            //     b: f32,
+            // }
+            adt::struct_def(p, m);
+        }
+        // test pub_macro_def
+        // pub macro m($:ident) {}
+        T![macro] => {
+            macro_def(p, m);
+        }
+        IDENT if p.at_contextual_kw("union") && p.nth(1) == IDENT => {
+            // test union_items
+            // union Foo {}
+            // union Foo {
+            //     a: i32,
+            //     b: f32,
+            // }
+            adt::union_def(p, m);
+        }
+        T![enum] => adt::enum_def(p, m),
+        T![use] => use_item::use_item(p, m),
+        T![const] if (la == IDENT || la == T![_] || la == T![mut]) => consts::const_def(p, m),
+        T![static] => consts::static_def(p, m),
+        // test extern_block
+        // extern {}
+        T![extern]
+            if la == T!['{'] || ((la == STRING || la == RAW_STRING) && p.nth(2) == T!['{']) =>
+        {
+            abi(p);
+            extern_item_list(p);
+            m.complete(p, EXTERN_BLOCK);
+        }
+        _ => return Err(m),
+    };
+    Ok(())
+}
+
+fn extern_crate_item(p: &mut Parser, m: Marker) {
+    assert!(p.at(T![extern]));
+    p.bump(T![extern]);
+    assert!(p.at(T![crate]));
+    p.bump(T![crate]);
+
+    if p.at(T![self]) {
+        p.bump(T![self]);
+    } else {
+        name_ref(p);
+    }
+
+    opt_alias(p);
+    p.expect(T![;]);
+    m.complete(p, EXTERN_CRATE);
+}
+
+pub(crate) fn extern_item_list(p: &mut Parser) {
+    assert!(p.at(T!['{']));
+    let m = p.start();
+    p.bump(T!['{']);
+    mod_contents(p, true);
+    p.expect(T!['}']);
+    m.complete(p, EXTERN_ITEM_LIST);
+}
+
+fn fn_def(p: &mut Parser) {
+    assert!(p.at(T![fn]));
+    p.bump(T![fn]);
+
+    name_r(p, ITEM_RECOVERY_SET);
+    // test function_type_params
+    // fn foo<T: Clone + Copy>(){}
+    type_params::opt_type_param_list(p);
+
+    if p.at(T!['(']) {
+        params::param_list_fn_def(p);
+    } else {
+        p.error("expected function arguments");
+    }
+    // test function_ret_type
+    // fn foo() {}
+    // fn bar() -> () {}
+    opt_fn_ret_type(p);
+
+    // test function_where_clause
+    // fn foo<T>() where T: Copy {}
+    type_params::opt_where_clause(p);
+
+    // test fn_decl
+    // trait T { fn foo(); }
+    if p.at(T![;]) {
+        p.bump(T![;]);
+    } else {
+        expressions::block_expr(p)
+    }
+}
+
+// test type_item
+// type Foo = Bar;
+fn type_def(p: &mut Parser, m: Marker) {
+    assert!(p.at(T![type]));
+    p.bump(T![type]);
+
+    name(p);
+
+    // test type_item_type_params
+    // type Result<T> = ();
+    type_params::opt_type_param_list(p);
+
+    if p.at(T![:]) {
+        type_params::bounds(p);
+    }
+
+    // test type_item_where_clause
+    // type Foo where Foo: Copy = ();
+    type_params::opt_where_clause(p);
+    if p.eat(T![=]) {
+        types::type_(p);
+    }
+    p.expect(T![;]);
+    m.complete(p, TYPE_ALIAS);
+}
+
+pub(crate) fn mod_item(p: &mut Parser, m: Marker) {
+    assert!(p.at(T![mod]));
+    p.bump(T![mod]);
+
+    name(p);
+    if p.at(T!['{']) {
+        mod_item_list(p);
+    } else if !p.eat(T![;]) {
+        p.error("expected `;` or `{`");
+    }
+    m.complete(p, MODULE);
+}
+
+pub(crate) fn mod_item_list(p: &mut Parser) {
+    assert!(p.at(T!['{']));
+    let m = p.start();
+    p.bump(T!['{']);
+    mod_contents(p, true);
+    p.expect(T!['}']);
+    m.complete(p, ITEM_LIST);
+}
+
+// test macro_def
+// macro m { ($i:ident) => {} }
+// macro m($i:ident) {}
+fn macro_def(p: &mut Parser, m: Marker) {
+    p.expect(T![macro]);
+    name_r(p, ITEM_RECOVERY_SET);
+    if p.at(T!['{']) {
+        token_tree(p);
+    } else if !p.at(T!['(']) {
+        p.error("unmatched `(`");
+    } else {
+        let m = p.start();
+        token_tree(p);
+        match p.current() {
+            T!['{'] | T!['['] | T!['('] => token_tree(p),
+            _ => p.error("expected `{`, `[`, `(`"),
+        }
+        m.complete(p, TOKEN_TREE);
+    }
+
+    m.complete(p, MACRO_DEF);
+}
+
+fn macro_call(p: &mut Parser) -> BlockLike {
+    assert!(paths::is_use_path_start(p));
+    paths::use_path(p);
+    macro_call_after_excl(p)
+}
+
+pub(super) fn macro_call_after_excl(p: &mut Parser) -> BlockLike {
+    p.expect(T![!]);
+    if p.at(IDENT) {
+        name(p);
+    }
+    // Special-case `macro_rules! try`.
+    // This is a hack until we do proper edition support
+
+    // test try_macro_rules
+    // macro_rules! try { () => {} }
+    if p.at(T![try]) {
+        let m = p.start();
+        p.bump_remap(IDENT);
+        m.complete(p, NAME);
+    }
+
+    match p.current() {
+        T!['{'] => {
+            token_tree(p);
+            BlockLike::Block
+        }
+        T!['('] | T!['['] => {
+            token_tree(p);
+            BlockLike::NotBlock
+        }
+        _ => {
+            p.error("expected `{`, `[`, `(`");
+            BlockLike::NotBlock
+        }
+    }
+}
+
+pub(crate) fn token_tree(p: &mut Parser) {
+    let closing_paren_kind = match p.current() {
+        T!['{'] => T!['}'],
+        T!['('] => T![')'],
+        T!['['] => T![']'],
+        _ => unreachable!(),
+    };
+    let m = p.start();
+    p.bump_any();
+    while !p.at(EOF) && !p.at(closing_paren_kind) {
+        match p.current() {
+            T!['{'] | T!['('] | T!['['] => token_tree(p),
+            T!['}'] => {
+                p.error("unmatched `}`");
+                m.complete(p, TOKEN_TREE);
+                return;
+            }
+            T![')'] | T![']'] => p.err_and_bump("unmatched brace"),
+            _ => p.bump_any(),
+        }
+    }
+    p.expect(closing_paren_kind);
+    m.complete(p, TOKEN_TREE);
+}