1 files changed, 611 insertions, 0 deletions

diff --git a/crates/parser/src/grammar/expressions/atom.rs b/crates/parser/src/grammar/expressions/atom.rs
new file mode 100644
index 000000000..0b01d3bc6
--- /dev/null
+++ b/crates/parser/src/grammar/expressions/atom.rs
@@ -0,0 +1,611 @@
+//! FIXME: write short doc here
+
+use super::*;
+
+// test expr_literals
+// fn foo() {
+//     let _ = true;
+//     let _ = false;
+//     let _ = 1;
+//     let _ = 2.0;
+//     let _ = b'a';
+//     let _ = 'b';
+//     let _ = "c";
+//     let _ = r"d";
+//     let _ = b"e";
+//     let _ = br"f";
+// }
+pub(crate) const LITERAL_FIRST: TokenSet = token_set![
+    TRUE_KW,
+    FALSE_KW,
+    INT_NUMBER,
+    FLOAT_NUMBER,
+    BYTE,
+    CHAR,
+    STRING,
+    RAW_STRING,
+    BYTE_STRING,
+    RAW_BYTE_STRING
+];
+
+pub(crate) fn literal(p: &mut Parser) -> Option<CompletedMarker> {
+    if !p.at_ts(LITERAL_FIRST) {
+        return None;
+    }
+    let m = p.start();
+    p.bump_any();
+    Some(m.complete(p, LITERAL))
+}
+
+// E.g. for after the break in `if break {}`, this should not match
+pub(super) const ATOM_EXPR_FIRST: TokenSet =
+    LITERAL_FIRST.union(paths::PATH_FIRST).union(token_set![
+        T!['('],
+        T!['{'],
+        T!['['],
+        L_DOLLAR,
+        T![|],
+        T![move],
+        T![box],
+        T![if],
+        T![while],
+        T![match],
+        T![unsafe],
+        T![return],
+        T![break],
+        T![continue],
+        T![async],
+        T![try],
+        T![loop],
+        T![for],
+        LIFETIME,
+    ]);
+
+const EXPR_RECOVERY_SET: TokenSet = token_set![LET_KW, R_DOLLAR];
+
+pub(super) fn atom_expr(p: &mut Parser, r: Restrictions) -> Option<(CompletedMarker, BlockLike)> {
+    if let Some(m) = literal(p) {
+        return Some((m, BlockLike::NotBlock));
+    }
+    if paths::is_path_start(p) {
+        return Some(path_expr(p, r));
+    }
+    let la = p.nth(1);
+    let done = match p.current() {
+        T!['('] => tuple_expr(p),
+        T!['['] => array_expr(p),
+        L_DOLLAR => meta_var_expr(p),
+        T![|] => lambda_expr(p),
+        T![move] if la == T![|] => lambda_expr(p),
+        T![async] if la == T![|] || (la == T![move] && p.nth(2) == T![|]) => lambda_expr(p),
+        T![if] => if_expr(p),
+
+        T![loop] => loop_expr(p, None),
+        T![box] => box_expr(p, None),
+        T![for] => for_expr(p, None),
+        T![while] => while_expr(p, None),
+        T![try] => try_block_expr(p, None),
+        LIFETIME if la == T![:] => {
+            let m = p.start();
+            label(p);
+            match p.current() {
+                T![loop] => loop_expr(p, Some(m)),
+                T![for] => for_expr(p, Some(m)),
+                T![while] => while_expr(p, Some(m)),
+                // test labeled_block
+                // fn f() { 'label: {}; }
+                T!['{'] => {
+                    block_expr(p);
+                    m.complete(p, EFFECT_EXPR)
+                }
+                _ => {
+                    // test_err misplaced_label_err
+                    // fn main() {
+                    //     'loop: impl
+                    // }
+                    p.error("expected a loop");
+                    m.complete(p, ERROR);
+                    return None;
+                }
+            }
+        }
+        T![async] if la == T!['{'] || (la == T![move] && p.nth(2) == T!['{']) => {
+            let m = p.start();
+            p.bump(T![async]);
+            p.eat(T![move]);
+            block_expr(p);
+            m.complete(p, EFFECT_EXPR)
+        }
+        T![match] => match_expr(p),
+        // test unsafe_block
+        // fn f() { unsafe { } }
+        T![unsafe] if la == T!['{'] => {
+            let m = p.start();
+            p.bump(T![unsafe]);
+            block_expr(p);
+            m.complete(p, EFFECT_EXPR)
+        }
+        T!['{'] => {
+            // test for_range_from
+            // fn foo() {
+            //    for x in 0 .. {
+            //        break;
+            //    }
+            // }
+            block_expr_unchecked(p)
+        }
+        T![return] => return_expr(p),
+        T![continue] => continue_expr(p),
+        T![break] => break_expr(p, r),
+        _ => {
+            p.err_recover("expected expression", EXPR_RECOVERY_SET);
+            return None;
+        }
+    };
+    let blocklike = match done.kind() {
+        IF_EXPR | WHILE_EXPR | FOR_EXPR | LOOP_EXPR | MATCH_EXPR | BLOCK_EXPR | EFFECT_EXPR => {
+            BlockLike::Block
+        }
+        _ => BlockLike::NotBlock,
+    };
+    Some((done, blocklike))
+}
+
+// test tuple_expr
+// fn foo() {
+//     ();
+//     (1);
+//     (1,);
+// }
+fn tuple_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(T!['(']));
+    let m = p.start();
+    p.expect(T!['(']);
+
+    let mut saw_comma = false;
+    let mut saw_expr = false;
+    while !p.at(EOF) && !p.at(T![')']) {
+        saw_expr = true;
+        if !p.at_ts(EXPR_FIRST) {
+            p.error("expected expression");
+            break;
+        }
+        expr(p);
+        if !p.at(T![')']) {
+            saw_comma = true;
+            p.expect(T![,]);
+        }
+    }
+    p.expect(T![')']);
+    m.complete(p, if saw_expr && !saw_comma { PAREN_EXPR } else { TUPLE_EXPR })
+}
+
+// test array_expr
+// fn foo() {
+//     [];
+//     [1];
+//     [1, 2,];
+//     [1; 2];
+// }
+fn array_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(T!['[']));
+    let m = p.start();
+
+    let mut n_exprs = 0u32;
+    let mut has_semi = false;
+
+    p.bump(T!['[']);
+    while !p.at(EOF) && !p.at(T![']']) {
+        n_exprs += 1;
+
+        // test array_attrs
+        // const A: &[i64] = &[1, #[cfg(test)] 2];
+        if !expr_with_attrs(p) {
+            break;
+        }
+
+        if n_exprs == 1 && p.eat(T![;]) {
+            has_semi = true;
+            continue;
+        }
+
+        if has_semi || !p.at(T![']']) && !p.expect(T![,]) {
+            break;
+        }
+    }
+    p.expect(T![']']);
+
+    m.complete(p, ARRAY_EXPR)
+}
+
+// test lambda_expr
+// fn foo() {
+//     || ();
+//     || -> i32 { 92 };
+//     |x| x;
+//     move |x: i32,| x;
+//     async || {};
+//     move || {};
+//     async move || {};
+// }
+fn lambda_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(
+        p.at(T![|])
+            || (p.at(T![move]) && p.nth(1) == T![|])
+            || (p.at(T![async]) && p.nth(1) == T![|])
+            || (p.at(T![async]) && p.nth(1) == T![move] && p.nth(2) == T![|])
+    );
+    let m = p.start();
+    p.eat(T![async]);
+    p.eat(T![move]);
+    params::param_list_closure(p);
+    if opt_fn_ret_type(p) {
+        // test lambda_ret_block
+        // fn main() { || -> i32 { 92 }(); }
+        block_expr(p);
+    } else {
+        if p.at_ts(EXPR_FIRST) {
+            expr(p);
+        } else {
+            p.error("expected expression");
+        }
+    }
+    m.complete(p, CLOSURE_EXPR)
+}
+
+// test if_expr
+// fn foo() {
+//     if true {};
+//     if true {} else {};
+//     if true {} else if false {} else {};
+//     if S {};
+//     if { true } { } else { };
+// }
+fn if_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(T![if]));
+    let m = p.start();
+    p.bump(T![if]);
+    cond(p);
+    block_expr(p);
+    if p.at(T![else]) {
+        p.bump(T![else]);
+        if p.at(T![if]) {
+            if_expr(p);
+        } else {
+            block_expr(p);
+        }
+    }
+    m.complete(p, IF_EXPR)
+}
+
+// test label
+// fn foo() {
+//     'a: loop {}
+//     'b: while true {}
+//     'c: for x in () {}
+// }
+fn label(p: &mut Parser) {
+    assert!(p.at(LIFETIME) && p.nth(1) == T![:]);
+    let m = p.start();
+    p.bump(LIFETIME);
+    p.bump_any();
+    m.complete(p, LABEL);
+}
+
+// test loop_expr
+// fn foo() {
+//     loop {};
+// }
+fn loop_expr(p: &mut Parser, m: Option<Marker>) -> CompletedMarker {
+    assert!(p.at(T![loop]));
+    let m = m.unwrap_or_else(|| p.start());
+    p.bump(T![loop]);
+    block_expr(p);
+    m.complete(p, LOOP_EXPR)
+}
+
+// test while_expr
+// fn foo() {
+//     while true {};
+//     while let Some(x) = it.next() {};
+//     while { true } {};
+// }
+fn while_expr(p: &mut Parser, m: Option<Marker>) -> CompletedMarker {
+    assert!(p.at(T![while]));
+    let m = m.unwrap_or_else(|| p.start());
+    p.bump(T![while]);
+    cond(p);
+    block_expr(p);
+    m.complete(p, WHILE_EXPR)
+}
+
+// test for_expr
+// fn foo() {
+//     for x in [] {};
+// }
+fn for_expr(p: &mut Parser, m: Option<Marker>) -> CompletedMarker {
+    assert!(p.at(T![for]));
+    let m = m.unwrap_or_else(|| p.start());
+    p.bump(T![for]);
+    patterns::pattern(p);
+    p.expect(T![in]);
+    expr_no_struct(p);
+    block_expr(p);
+    m.complete(p, FOR_EXPR)
+}
+
+// test cond
+// fn foo() { if let Some(_) = None {} }
+// fn bar() {
+//     if let Some(_) | Some(_) = None {}
+//     if let | Some(_) = None {}
+//     while let Some(_) | Some(_) = None {}
+//     while let | Some(_) = None {}
+// }
+fn cond(p: &mut Parser) {
+    let m = p.start();
+    if p.eat(T![let]) {
+        patterns::pattern_top(p);
+        p.expect(T![=]);
+    }
+    expr_no_struct(p);
+    m.complete(p, CONDITION);
+}
+
+// test match_expr
+// fn foo() {
+//     match () { };
+//     match S {};
+//     match { } { _ => () };
+//     match { S {} } {};
+// }
+fn match_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(T![match]));
+    let m = p.start();
+    p.bump(T![match]);
+    expr_no_struct(p);
+    if p.at(T!['{']) {
+        match_arm_list(p);
+    } else {
+        p.error("expected `{`")
+    }
+    m.complete(p, MATCH_EXPR)
+}
+
+pub(crate) fn match_arm_list(p: &mut Parser) {
+    assert!(p.at(T!['{']));
+    let m = p.start();
+    p.eat(T!['{']);
+
+    // test match_arms_inner_attribute
+    // fn foo() {
+    //     match () {
+    //         #![doc("Inner attribute")]
+    //         #![doc("Can be")]
+    //         #![doc("Stacked")]
+    //         _ => (),
+    //     }
+    // }
+    attributes::inner_attributes(p);
+
+    while !p.at(EOF) && !p.at(T!['}']) {
+        if p.at(T!['{']) {
+            error_block(p, "expected match arm");
+            continue;
+        }
+
+        // test match_arms_commas
+        // fn foo() {
+        //     match () {
+        //         _ => (),
+        //         _ => {}
+        //         _ => ()
+        //     }
+        // }
+        if match_arm(p).is_block() {
+            p.eat(T![,]);
+        } else if !p.at(T!['}']) {
+            p.expect(T![,]);
+        }
+    }
+    p.expect(T!['}']);
+    m.complete(p, MATCH_ARM_LIST);
+}
+
+// test match_arm
+// fn foo() {
+//     match () {
+//         _ => (),
+//         _ if Test > Test{field: 0} => (),
+//         X | Y if Z => (),
+//         | X | Y if Z => (),
+//         | X => (),
+//     };
+// }
+fn match_arm(p: &mut Parser) -> BlockLike {
+    let m = p.start();
+    // test match_arms_outer_attributes
+    // fn foo() {
+    //     match () {
+    //         #[cfg(feature = "some")]
+    //         _ => (),
+    //         #[cfg(feature = "other")]
+    //         _ => (),
+    //         #[cfg(feature = "many")]
+    //         #[cfg(feature = "attributes")]
+    //         #[cfg(feature = "before")]
+    //         _ => (),
+    //     }
+    // }
+    attributes::outer_attributes(p);
+
+    patterns::pattern_top_r(p, TokenSet::EMPTY);
+    if p.at(T![if]) {
+        match_guard(p);
+    }
+    p.expect(T![=>]);
+    let blocklike = expr_stmt(p).1;
+    m.complete(p, MATCH_ARM);
+    blocklike
+}
+
+// test match_guard
+// fn foo() {
+//     match () {
+//         _ if foo => (),
+//     }
+// }
+fn match_guard(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(T![if]));
+    let m = p.start();
+    p.bump(T![if]);
+    expr(p);
+    m.complete(p, MATCH_GUARD)
+}
+
+// test block
+// fn a() {}
+// fn b() { let _ = 1; }
+// fn c() { 1; 2; }
+// fn d() { 1; 2 }
+pub(crate) fn block_expr(p: &mut Parser) {
+    if !p.at(T!['{']) {
+        p.error("expected a block");
+        return;
+    }
+    block_expr_unchecked(p);
+}
+
+fn block_expr_unchecked(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(T!['{']));
+    let m = p.start();
+    p.bump(T!['{']);
+    expr_block_contents(p);
+    p.expect(T!['}']);
+    m.complete(p, BLOCK_EXPR)
+}
+
+// test return_expr
+// fn foo() {
+//     return;
+//     return 92;
+// }
+fn return_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(T![return]));
+    let m = p.start();
+    p.bump(T![return]);
+    if p.at_ts(EXPR_FIRST) {
+        expr(p);
+    }
+    m.complete(p, RETURN_EXPR)
+}
+
+// test continue_expr
+// fn foo() {
+//     loop {
+//         continue;
+//         continue 'l;
+//     }
+// }
+fn continue_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(T![continue]));
+    let m = p.start();
+    p.bump(T![continue]);
+    p.eat(LIFETIME);
+    m.complete(p, CONTINUE_EXPR)
+}
+
+// test break_expr
+// fn foo() {
+//     loop {
+//         break;
+//         break 'l;
+//         break 92;
+//         break 'l 92;
+//     }
+// }
+fn break_expr(p: &mut Parser, r: Restrictions) -> CompletedMarker {
+    assert!(p.at(T![break]));
+    let m = p.start();
+    p.bump(T![break]);
+    p.eat(LIFETIME);
+    // test break_ambiguity
+    // fn foo(){
+    //     if break {}
+    //     while break {}
+    //     for i in break {}
+    //     match break {}
+    // }
+    if p.at_ts(EXPR_FIRST) && !(r.forbid_structs && p.at(T!['{'])) {
+        expr(p);
+    }
+    m.complete(p, BREAK_EXPR)
+}
+
+// test try_block_expr
+// fn foo() {
+//     let _ = try {};
+// }
+fn try_block_expr(p: &mut Parser, m: Option<Marker>) -> CompletedMarker {
+    assert!(p.at(T![try]));
+    let m = m.unwrap_or_else(|| p.start());
+    // Special-case `try!` as macro.
+    // This is a hack until we do proper edition support
+    if p.nth_at(1, T![!]) {
+        // test try_macro_fallback
+        // fn foo() { try!(Ok(())); }
+        let path = p.start();
+        let path_segment = p.start();
+        let name_ref = p.start();
+        p.bump_remap(IDENT);
+        name_ref.complete(p, NAME_REF);
+        path_segment.complete(p, PATH_SEGMENT);
+        path.complete(p, PATH);
+        let _block_like = items::macro_call_after_excl(p);
+        return m.complete(p, MACRO_CALL);
+    }
+
+    p.bump(T![try]);
+    block_expr(p);
+    m.complete(p, EFFECT_EXPR)
+}
+
+// test box_expr
+// fn foo() {
+//     let x = box 1i32;
+//     let y = (box 1i32, box 2i32);
+//     let z = Foo(box 1i32, box 2i32);
+// }
+fn box_expr(p: &mut Parser, m: Option<Marker>) -> CompletedMarker {
+    assert!(p.at(T![box]));
+    let m = m.unwrap_or_else(|| p.start());
+    p.bump(T![box]);
+    if p.at_ts(EXPR_FIRST) {
+        expr(p);
+    }
+    m.complete(p, BOX_EXPR)
+}
+
+/// Expression from `$var` macro expansion, wrapped in dollars
+fn meta_var_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(L_DOLLAR));
+    let m = p.start();
+    p.bump(L_DOLLAR);
+    let (completed, _is_block) =
+        expr_bp(p, Restrictions { forbid_structs: false, prefer_stmt: false }, 1);
+
+    match (completed, p.current()) {
+        (Some(it), R_DOLLAR) => {
+            p.bump(R_DOLLAR);
+            m.abandon(p);
+            it
+        }
+        _ => {
+            while !p.at(R_DOLLAR) {
+                p.bump_any()
+            }
+            p.bump(R_DOLLAR);
+            m.complete(p, ERROR)
+        }
+    }
+}