2 files changed, 494 insertions, 0 deletions

diff --git a/src/grammar/expressions/atom.rs b/src/grammar/expressions/atom.rs
new file mode 100644
index 000000000..95c811730
--- /dev/null
+++ b/src/grammar/expressions/atom.rs
@@ -0,0 +1,239 @@
+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";
+// }
+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 !LITERAL_FIRST.contains(p.current()) {
+        return None;
+    }
+    let m = p.start();
+    p.bump();
+    Some(m.complete(p, LITERAL))
+}
+
+pub(super) const ATOM_EXPR_FIRST: TokenSet =
+    token_set_union![
+        LITERAL_FIRST,
+        token_set![L_PAREN, PIPE, MOVE_KW, IF_KW, MATCH_KW, UNSAFE_KW, L_CURLY, RETURN_KW,
+                   IDENT, SELF_KW, SUPER_KW, COLONCOLON ],
+    ];
+
+pub(super) fn atom_expr(p: &mut Parser) -> Option<CompletedMarker> {
+    match literal(p) {
+        Some(m) => return Some(m),
+        None => (),
+    }
+    if paths::is_path_start(p) {
+        return Some(path_expr(p));
+    }
+    let la = p.nth(1);
+    let done = match p.current() {
+        L_PAREN => tuple_expr(p),
+        PIPE => lambda_expr(p),
+        MOVE_KW if la == PIPE => lambda_expr(p),
+        IF_KW => if_expr(p),
+        MATCH_KW => match_expr(p),
+        UNSAFE_KW if la == L_CURLY => block_expr(p),
+        L_CURLY => block_expr(p),
+        RETURN_KW => return_expr(p),
+        _ => {
+            p.err_and_bump("expected expression");
+            return None;
+        }
+    };
+    Some(done)
+}
+
+fn tuple_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(L_PAREN));
+    let m = p.start();
+    p.expect(L_PAREN);
+    p.expect(R_PAREN);
+    m.complete(p, TUPLE_EXPR)
+}
+
+// test lambda_expr
+// fn foo() {
+//     || ();
+//     || -> i32 { 92 };
+//     |x| x;
+//     move |x: i32,| x;
+// }
+fn lambda_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(PIPE) || (p.at(MOVE_KW) && p.nth(1) == PIPE));
+    let m = p.start();
+    p.eat(MOVE_KW);
+    params::param_list_opt_types(p);
+    if fn_ret_type(p) {
+        block(p);
+    } else {
+        expr(p)
+    }
+    m.complete(p, LAMBDA_EXPR)
+}
+
+// test if_expr
+// fn foo() {
+//     if true {};
+//     if true {} else {};
+//     if true {} else if false {} else {}
+// }
+fn if_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(IF_KW));
+    let m = p.start();
+    if_head(p);
+    block(p);
+    if p.at(ELSE_KW) {
+        p.bump();
+        if p.at(IF_KW) {
+            if_expr(p);
+        } else {
+            block(p);
+        }
+    }
+    m.complete(p, IF_EXPR)
+}
+
+fn if_head(p: &mut Parser) {
+    assert!(p.at(IF_KW));
+    p.bump();
+    expr(p);
+}
+
+// test match_expr
+// fn foo() {
+//     match () { };
+// }
+fn match_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(MATCH_KW));
+    let m = p.start();
+    p.bump();
+    expr(p);
+    p.eat(L_CURLY);
+    while !p.at(EOF) && !p.at(R_CURLY) {
+        match_arm(p);
+        if !p.at(R_CURLY) {
+            p.expect(COMMA);
+        }
+    }
+    p.expect(R_CURLY);
+    m.complete(p, MATCH_EXPR)
+}
+
+// test match_arm
+// fn foo() {
+//     match () {
+//         _ => (),
+//         X | Y if Z => (),
+//     };
+// }
+fn match_arm(p: &mut Parser) {
+    let m = p.start();
+    loop {
+        patterns::pattern(p);
+        if !p.eat(PIPE) {
+            break;
+        }
+    }
+    if p.at(IF_KW) {
+        if_head(p)
+    }
+    p.expect(FAT_ARROW);
+    expr(p);
+    m.complete(p, MATCH_ARM);
+}
+
+// test block_expr
+// fn foo() {
+//     {};
+//     unsafe {};
+// }
+pub(super) fn block_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(L_CURLY) || p.at(UNSAFE_KW) && p.nth(1) == L_CURLY);
+    let m = p.start();
+    p.eat(UNSAFE_KW);
+    p.bump();
+    while !p.at(EOF) && !p.at(R_CURLY) {
+        match p.current() {
+            LET_KW => let_stmt(p),
+            _ => {
+                // test block_items
+                // fn a() { fn b() {} }
+                let m = p.start();
+                match items::maybe_item(p) {
+                    items::MaybeItem::Item(kind) => {
+                        m.complete(p, kind);
+                    }
+                    items::MaybeItem::Modifiers => {
+                        m.abandon(p);
+                        p.error("expected an item");
+                    }
+                    // test pub_expr
+                    // fn foo() { pub 92; } //FIXME
+                    items::MaybeItem::None => {
+                        expressions::expr(p);
+                        if p.eat(SEMI) {
+                            m.complete(p, EXPR_STMT);
+                        } else {
+                            m.abandon(p);
+                        }
+                    }
+                }
+            }
+        }
+    }
+    p.expect(R_CURLY);
+    m.complete(p, BLOCK_EXPR)
+}
+
+// test let_stmt;
+// fn foo() {
+//     let a;
+//     let b: i32;
+//     let c = 92;
+//     let d: i32 = 92;
+// }
+fn let_stmt(p: &mut Parser) {
+    assert!(p.at(LET_KW));
+    let m = p.start();
+    p.bump();
+    patterns::pattern(p);
+    if p.at(COLON) {
+        types::ascription(p);
+    }
+    if p.eat(EQ) {
+        expressions::expr(p);
+    }
+    p.expect(SEMI);
+    m.complete(p, LET_STMT);
+}
+
+// test return_expr
+// fn foo() {
+//     return;
+//     return 92;
+// }
+fn return_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(RETURN_KW));
+    let m = p.start();
+    p.bump();
+    if EXPR_FIRST.contains(p.current()) {
+        expr(p);
+    }
+    m.complete(p, RETURN_EXPR)
+}
diff --git a/src/grammar/expressions/mod.rs b/src/grammar/expressions/mod.rs
new file mode 100644
index 000000000..f2b0c36f5
--- /dev/null
+++ b/src/grammar/expressions/mod.rs
@@ -0,0 +1,255 @@
+mod atom;
+
+use super::*;
+pub(super) use self::atom::literal;
+
+const EXPR_FIRST: TokenSet = UNARY_EXPR_FIRST;
+
+pub(super) fn expr(p: &mut Parser) {
+    expr_bp(p, 1)
+}
+
+// test block
+// fn a() {}
+// fn b() { let _ = 1; }
+// fn c() { 1; 2; }
+// fn d() { 1; 2 }
+pub(super) fn block(p: &mut Parser) {
+    if !p.at(L_CURLY) {
+        p.error("expected block");
+        return;
+    }
+    atom::block_expr(p);
+}
+
+// test expr_binding_power
+// fn foo() {
+//     1 + 2 * 3 == 1 * 2 + 3
+// }
+fn bp_of(op: SyntaxKind) -> u8 {
+    match op {
+        EQEQ | NEQ => 1,
+        MINUS | PLUS => 2,
+        STAR | SLASH => 3,
+        _ => 0
+    }
+}
+
+// Parses expression with binding power of at least bp.
+fn expr_bp(p: &mut Parser, bp: u8) {
+    let mut lhs = match unary_expr(p) {
+        Some(lhs) => lhs,
+        None => return,
+    };
+
+    loop {
+        let op_bp = bp_of(p.current());
+        if op_bp < bp {
+            break;
+        }
+        lhs = bin_expr(p, lhs, op_bp);
+    }
+}
+
+const UNARY_EXPR_FIRST: TokenSet =
+    token_set_union![
+        token_set![AMPERSAND, STAR, EXCL],
+        atom::ATOM_EXPR_FIRST,
+    ];
+
+fn unary_expr(p: &mut Parser) -> Option<CompletedMarker> {
+    let done = match p.current() {
+        AMPERSAND => ref_expr(p),
+        STAR => deref_expr(p),
+        EXCL => not_expr(p),
+        _ => {
+            let lhs = atom::atom_expr(p)?;
+            postfix_expr(p, lhs)
+        }
+    };
+    Some(done)
+}
+
+fn postfix_expr(p: &mut Parser, mut lhs: CompletedMarker) -> CompletedMarker {
+    loop {
+        lhs = match p.current() {
+            L_PAREN => call_expr(p, lhs),
+            DOT if p.nth(1) == IDENT => if p.nth(2) == L_PAREN {
+                method_call_expr(p, lhs)
+            } else {
+                field_expr(p, lhs)
+            },
+            DOT if p.nth(1) == INT_NUMBER => field_expr(p, lhs),
+            QUESTION => try_expr(p, lhs),
+            _ => break,
+        }
+    }
+    lhs
+}
+
+// test ref_expr
+// fn foo() {
+//     let _ = &1;
+//     let _ = &mut &f();
+// }
+fn ref_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(AMPERSAND));
+    let m = p.start();
+    p.bump();
+    p.eat(MUT_KW);
+    expr(p);
+    m.complete(p, REF_EXPR)
+}
+
+// test deref_expr
+// fn foo() {
+//     **&1;
+// }
+fn deref_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(STAR));
+    let m = p.start();
+    p.bump();
+    expr(p);
+    m.complete(p, DEREF_EXPR)
+}
+
+// test not_expr
+// fn foo() {
+//     !!true;
+// }
+fn not_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(EXCL));
+    let m = p.start();
+    p.bump();
+    expr(p);
+    m.complete(p, NOT_EXPR)
+}
+
+// test call_expr
+// fn foo() {
+//     let _ = f();
+//     let _ = f()(1)(1, 2,);
+// }
+fn call_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
+    assert!(p.at(L_PAREN));
+    let m = lhs.precede(p);
+    arg_list(p);
+    m.complete(p, CALL_EXPR)
+}
+
+// test method_call_expr
+// fn foo() {
+//     x.foo();
+//     y.bar(1, 2,);
+// }
+fn method_call_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
+    assert!(p.at(DOT) && p.nth(1) == IDENT && p.nth(2) == L_PAREN);
+    let m = lhs.precede(p);
+    p.bump();
+    name_ref(p);
+    arg_list(p);
+    m.complete(p, METHOD_CALL_EXPR)
+}
+
+// test field_expr
+// fn foo() {
+//     x.foo;
+//     x.0.bar;
+// }
+fn field_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
+    assert!(p.at(DOT) && (p.nth(1) == IDENT || p.nth(1) == INT_NUMBER));
+    let m = lhs.precede(p);
+    p.bump();
+    if p.at(IDENT) {
+        name_ref(p)
+    } else {
+        p.bump()
+    }
+    m.complete(p, FIELD_EXPR)
+}
+
+// test try_expr
+// fn foo() {
+//     x?;
+// }
+fn try_expr(p: &mut Parser, lhs: CompletedMarker) -> CompletedMarker {
+    assert!(p.at(QUESTION));
+    let m = lhs.precede(p);
+    p.bump();
+    m.complete(p, TRY_EXPR)
+}
+
+fn arg_list(p: &mut Parser) {
+    assert!(p.at(L_PAREN));
+    let m = p.start();
+    p.bump();
+    while !p.at(R_PAREN) && !p.at(EOF) {
+        expr(p);
+        if !p.at(R_PAREN) && !p.expect(COMMA) {
+            break;
+        }
+    }
+    p.eat(R_PAREN);
+    m.complete(p, ARG_LIST);
+}
+
+// test path_expr
+// fn foo() {
+//     let _ = a;
+//     let _ = a::b;
+//     let _ = ::a::<b>;
+// }
+fn path_expr(p: &mut Parser) -> CompletedMarker {
+    assert!(paths::is_path_start(p));
+    let m = p.start();
+    paths::expr_path(p);
+    if p.at(L_CURLY) {
+        struct_lit(p);
+        m.complete(p, STRUCT_LIT)
+    } else {
+        m.complete(p, PATH_EXPR)
+    }
+}
+
+// test struct_lit
+// fn foo() {
+//     S {};
+//     S { x, y: 32, };
+//     S { x, y: 32, ..Default::default() };
+// }
+fn struct_lit(p: &mut Parser) {
+    assert!(p.at(L_CURLY));
+    p.bump();
+    while !p.at(EOF) && !p.at(R_CURLY) {
+        match p.current() {
+            IDENT => {
+                let m = p.start();
+                name_ref(p);
+                if p.eat(COLON) {
+                    expr(p);
+                }
+                m.complete(p, STRUCT_LIT_FIELD);
+            }
+            DOTDOT => {
+                p.bump();
+                expr(p);
+            }
+            _ => p.err_and_bump("expected identifier"),
+        }
+        if !p.at(R_CURLY) {
+            p.expect(COMMA);
+        }
+    }
+    p.expect(R_CURLY);
+}
+
+fn bin_expr(p: &mut Parser, lhs: CompletedMarker, bp: u8) -> CompletedMarker {
+    assert!(match p.current() {
+        MINUS | PLUS | STAR | SLASH | EQEQ | NEQ => true,
+        _ => false,
+    });
+    let m = lhs.precede(p);
+    p.bump();
+    expr_bp(p, bp);
+    m.complete(p, BIN_EXPR)
+}