1 files changed, 224 insertions, 0 deletions

diff --git a/crates/ra_syntax/src/grammar/patterns.rs b/crates/ra_syntax/src/grammar/patterns.rs
new file mode 100644
index 000000000..420bae7a7
--- /dev/null
+++ b/crates/ra_syntax/src/grammar/patterns.rs
@@ -0,0 +1,224 @@
+use super::*;
+
+pub(super) const PATTERN_FIRST: TokenSet =
+    token_set_union![
+        token_set![REF_KW, MUT_KW, L_PAREN, L_BRACK, AMP, UNDERSCORE],
+        expressions::LITERAL_FIRST,
+        paths::PATH_FIRST,
+    ];
+
+pub(super) fn pattern(p: &mut Parser) {
+    pattern_r(p, PAT_RECOVERY_SET)
+}
+
+pub(super) fn pattern_r(p: &mut Parser, recovery_set: TokenSet) {
+    if let Some(lhs) = atom_pat(p, recovery_set) {
+        // test range_pat
+        // fn main() {
+        //     match 92 { 0 ... 100 => () }
+        // }
+        if p.at(DOTDOTDOT) {
+            let m = lhs.precede(p);
+            p.bump();
+            atom_pat(p, recovery_set);
+            m.complete(p, RANGE_PAT);
+        }
+    }
+}
+
+const PAT_RECOVERY_SET: TokenSet =
+    token_set![LET_KW, IF_KW, WHILE_KW, LOOP_KW, MATCH_KW, R_PAREN, COMMA];
+
+
+fn atom_pat(p: &mut Parser, recovery_set: TokenSet) -> Option<CompletedMarker> {
+    let la0 = p.nth(0);
+    let la1 = p.nth(1);
+    if la0 == REF_KW || la0 == MUT_KW
+        || (la0 == IDENT && !(la1 == COLONCOLON || la1 == L_PAREN || la1 == L_CURLY)) {
+        return Some(bind_pat(p, true));
+    }
+    if paths::is_path_start(p) {
+        return Some(path_pat(p));
+    }
+
+    // test literal_pattern
+    // fn main() {
+    //     match () {
+    //         92 => (),
+    //         'c' => (),
+    //         "hello" => (),
+    //     }
+    // }
+    match expressions::literal(p) {
+        Some(m) => return Some(m),
+        None => (),
+    }
+
+    let m = match la0 {
+        UNDERSCORE => placeholder_pat(p),
+        AMP => ref_pat(p),
+        L_PAREN => tuple_pat(p),
+        L_BRACK => slice_pat(p),
+        _ => {
+            p.err_recover("expected pattern", recovery_set);
+            return None;
+        }
+    };
+    Some(m)
+}
+
+// test path_part
+// fn foo() {
+//     let foo::Bar = ();
+//     let ::Bar = ();
+//     let Bar { .. } = ();
+//     let Bar(..) = ();
+// }
+fn path_pat(p: &mut Parser) -> CompletedMarker {
+    assert!(paths::is_path_start(p));
+    let m = p.start();
+    paths::expr_path(p);
+    let kind = match p.current() {
+        L_PAREN => {
+            tuple_pat_fields(p);
+            TUPLE_STRUCT_PAT
+        }
+        L_CURLY => {
+            field_pat_list(p);
+            STRUCT_PAT
+        }
+        _ => PATH_PAT
+    };
+    m.complete(p, kind)
+}
+
+// test tuple_pat_fields
+// fn foo() {
+//     let S() = ();
+//     let S(_) = ();
+//     let S(_,) = ();
+//     let S(_, .. , x) = ();
+// }
+fn tuple_pat_fields(p: &mut Parser) {
+    assert!(p.at(L_PAREN));
+    p.bump();
+    pat_list(p, R_PAREN);
+    p.expect(R_PAREN);
+}
+
+// test field_pat_list
+// fn foo() {
+//     let S {} = ();
+//     let S { f, ref mut g } = ();
+//     let S { h: _, ..} = ();
+//     let S { h: _, } = ();
+// }
+fn field_pat_list(p: &mut Parser) {
+    assert!(p.at(L_CURLY));
+    let m = p.start();
+    p.bump();
+    while !p.at(EOF) && !p.at(R_CURLY) {
+        match p.current() {
+            DOTDOT => p.bump(),
+            IDENT if p.nth(1) == COLON => {
+                p.bump();
+                p.bump();
+                pattern(p);
+            }
+            L_CURLY => error_block(p, "expected ident"),
+            _ => {
+                bind_pat(p, false);
+            }
+        }
+        if !p.at(R_CURLY) {
+            p.expect(COMMA);
+        }
+    }
+    p.expect(R_CURLY);
+    m.complete(p, FIELD_PAT_LIST);
+}
+
+// test placeholder_pat
+// fn main() { let _ = (); }
+fn placeholder_pat(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(UNDERSCORE));
+    let m = p.start();
+    p.bump();
+    m.complete(p, PLACEHOLDER_PAT)
+}
+
+// test ref_pat
+// fn main() {
+//     let &a = ();
+//     let &mut b = ();
+// }
+fn ref_pat(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(AMP));
+    let m = p.start();
+    p.bump();
+    p.eat(MUT_KW);
+    pattern(p);
+    m.complete(p, REF_PAT)
+}
+
+// test tuple_pat
+// fn main() {
+//     let (a, b, ..) = ();
+// }
+fn tuple_pat(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(L_PAREN));
+    let m = p.start();
+    tuple_pat_fields(p);
+    m.complete(p, TUPLE_PAT)
+}
+
+// test slice_pat
+// fn main() {
+//     let [a, b, ..] = [];
+// }
+fn slice_pat(p: &mut Parser) -> CompletedMarker {
+    assert!(p.at(L_BRACK));
+    let m = p.start();
+    p.bump();
+    pat_list(p, R_BRACK);
+    p.expect(R_BRACK);
+    m.complete(p, SLICE_PAT)
+}
+
+fn pat_list(p: &mut Parser, ket: SyntaxKind) {
+    while !p.at(EOF) && !p.at(ket) {
+        match p.current() {
+            DOTDOT => p.bump(),
+            _ => {
+                if !p.at_ts(PATTERN_FIRST) {
+                    p.error("expected a pattern");
+                    break;
+                }
+                pattern(p)
+            },
+        }
+        if !p.at(ket) {
+            p.expect(COMMA);
+        }
+    }
+}
+
+// test bind_pat
+// fn main() {
+//     let a = ();
+//     let mut b = ();
+//     let ref c = ();
+//     let ref mut d = ();
+//     let e @ _ = ();
+//     let ref mut f @ g @ _ = ();
+// }
+fn bind_pat(p: &mut Parser, with_at: bool) -> CompletedMarker {
+    let m = p.start();
+    p.eat(REF_KW);
+    p.eat(MUT_KW);
+    name(p);
+    if with_at && p.eat(AT) {
+        pattern(p);
+    }
+    m.complete(p, BIND_PAT)
+}