8 files changed, 52 insertions, 57 deletions

diff --git a/crates/ra_syntax/src/grammar.rs b/crates/ra_syntax/src/grammar.rs
index 06a37d648..060c0ccdf 100644
--- a/crates/ra_syntax/src/grammar.rs
+++ b/crates/ra_syntax/src/grammar.rs
@@ -150,7 +150,7 @@ fn name_r(p: &mut Parser, recovery: TokenSet) {
 }
 
 fn name(p: &mut Parser) {
-    name_r(p, TokenSet::EMPTY)
+    name_r(p, TokenSet::empty())
 }
 
 fn name_ref(p: &mut Parser) {
diff --git a/crates/ra_syntax/src/grammar/expressions.rs b/crates/ra_syntax/src/grammar/expressions.rs
index 2d1f17491..2236555e0 100644
--- a/crates/ra_syntax/src/grammar/expressions.rs
+++ b/crates/ra_syntax/src/grammar/expressions.rs
@@ -211,10 +211,8 @@ fn expr_bp(p: &mut Parser, r: Restrictions, bp: u8) -> BlockLike {
     BlockLike::NotBlock
 }
 
-const LHS_FIRST: TokenSet = token_set_union![
-    token_set![AMP, STAR, EXCL, DOTDOT, DOTDOTEQ, MINUS],
-    atom::ATOM_EXPR_FIRST,
-];
+const LHS_FIRST: TokenSet =
+    atom::ATOM_EXPR_FIRST.union(token_set![AMP, STAR, EXCL, DOTDOT, DOTDOTEQ, MINUS]);
 
 fn lhs(p: &mut Parser, r: Restrictions) -> Option<(CompletedMarker, BlockLike)> {
     let m;
diff --git a/crates/ra_syntax/src/grammar/expressions/atom.rs b/crates/ra_syntax/src/grammar/expressions/atom.rs
index 31b09ac5b..167a76551 100644
--- a/crates/ra_syntax/src/grammar/expressions/atom.rs
+++ b/crates/ra_syntax/src/grammar/expressions/atom.rs
@@ -36,29 +36,26 @@ pub(crate) fn literal(p: &mut Parser) -> Option<CompletedMarker> {
 }
 
 // E.g. for after the break in `if break {}`, this should not match
-pub(super) const ATOM_EXPR_FIRST: TokenSet = token_set_union![
-    LITERAL_FIRST,
-    token_set![
-        L_PAREN,
-        L_CURLY,
-        L_BRACK,
-        PIPE,
-        MOVE_KW,
-        IF_KW,
-        WHILE_KW,
-        MATCH_KW,
-        UNSAFE_KW,
-        RETURN_KW,
-        IDENT,
-        SELF_KW,
-        SUPER_KW,
-        CRATE_KW,
-        COLONCOLON,
-        BREAK_KW,
-        CONTINUE_KW,
-        LIFETIME
-    ],
-];
+pub(super) const ATOM_EXPR_FIRST: TokenSet = LITERAL_FIRST.union(token_set![
+    L_PAREN,
+    L_CURLY,
+    L_BRACK,
+    PIPE,
+    MOVE_KW,
+    IF_KW,
+    WHILE_KW,
+    MATCH_KW,
+    UNSAFE_KW,
+    RETURN_KW,
+    IDENT,
+    SELF_KW,
+    SUPER_KW,
+    CRATE_KW,
+    COLONCOLON,
+    BREAK_KW,
+    CONTINUE_KW,
+    LIFETIME,
+]);
 
 const EXPR_RECOVERY_SET: TokenSet = token_set![LET_KW];
 
@@ -363,7 +360,7 @@ pub(crate) fn match_arm_list(p: &mut Parser) {
 fn match_arm(p: &mut Parser) -> BlockLike {
     let m = p.start();
     p.eat(PIPE);
-    patterns::pattern_r(p, TokenSet::EMPTY);
+    patterns::pattern_r(p, TokenSet::empty());
     while p.eat(PIPE) {
         patterns::pattern(p);
     }
diff --git a/crates/ra_syntax/src/grammar/params.rs b/crates/ra_syntax/src/grammar/params.rs
index b71a72ca3..658fc5820 100644
--- a/crates/ra_syntax/src/grammar/params.rs
+++ b/crates/ra_syntax/src/grammar/params.rs
@@ -61,8 +61,7 @@ fn list_(p: &mut Parser, flavor: Flavor) {
     m.complete(p, PARAM_LIST);
 }
 
-const VALUE_PARAMETER_FIRST: TokenSet =
-    token_set_union![patterns::PATTERN_FIRST, types::TYPE_FIRST,];
+const VALUE_PARAMETER_FIRST: TokenSet = patterns::PATTERN_FIRST.union(types::TYPE_FIRST);
 
 fn value_parameter(p: &mut Parser, flavor: Flavor) {
     let m = p.start();
diff --git a/crates/ra_syntax/src/grammar/patterns.rs b/crates/ra_syntax/src/grammar/patterns.rs
index 692ffbb8c..7820c4e02 100644
--- a/crates/ra_syntax/src/grammar/patterns.rs
+++ b/crates/ra_syntax/src/grammar/patterns.rs
@@ -1,10 +1,10 @@
 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) const PATTERN_FIRST: TokenSet = expressions::LITERAL_FIRST
+    .union(paths::PATH_FIRST)
+    .union(token_set![
+        REF_KW, MUT_KW, L_PAREN, L_BRACK, AMP, UNDERSCORE
+    ]);
 
 pub(super) fn pattern(p: &mut Parser) {
     pattern_r(p, PAT_RECOVERY_SET)
diff --git a/crates/ra_syntax/src/grammar/types.rs b/crates/ra_syntax/src/grammar/types.rs
index a933b986b..21d89d83b 100644
--- a/crates/ra_syntax/src/grammar/types.rs
+++ b/crates/ra_syntax/src/grammar/types.rs
@@ -1,12 +1,9 @@
 use super::*;
 
-pub(super) const TYPE_FIRST: TokenSet = token_set_union![
-    token_set![
-        L_PAREN, EXCL, STAR, L_BRACK, AMP, UNDERSCORE, FN_KW, UNSAFE_KW, EXTERN_KW, FOR_KW,
-        IMPL_KW, DYN_KW, L_ANGLE,
-    ],
-    paths::PATH_FIRST,
-];
+pub(super) const TYPE_FIRST: TokenSet = paths::PATH_FIRST.union(token_set![
+    L_PAREN, EXCL, STAR, L_BRACK, AMP, UNDERSCORE, FN_KW, UNSAFE_KW, EXTERN_KW, FOR_KW, IMPL_KW,
+    DYN_KW, L_ANGLE,
+]);
 
 const TYPE_RECOVERY_SET: TokenSet = token_set![R_PAREN, COMMA];
 
diff --git a/crates/ra_syntax/src/parser_api.rs b/crates/ra_syntax/src/parser_api.rs
index 3487aef85..3148371c5 100644
--- a/crates/ra_syntax/src/parser_api.rs
+++ b/crates/ra_syntax/src/parser_api.rs
@@ -112,7 +112,7 @@ impl<'t> Parser<'t> {
 
     /// Create an error node and consume the next token.
     pub(crate) fn err_and_bump(&mut self, message: &str) {
-        self.err_recover(message, TokenSet::EMPTY);
+        self.err_recover(message, TokenSet::empty());
     }
 
     /// Create an error node and consume the next token.
diff --git a/crates/ra_syntax/src/token_set.rs b/crates/ra_syntax/src/token_set.rs
index d407dfa48..b3fe633e0 100644
--- a/crates/ra_syntax/src/token_set.rs
+++ b/crates/ra_syntax/src/token_set.rs
@@ -1,30 +1,34 @@
 use crate::SyntaxKind;
 
 #[derive(Clone, Copy)]
-pub(crate) struct TokenSet(pub(crate) u128);
-
-fn mask(kind: SyntaxKind) -> u128 {
-    1u128 << (kind as usize)
-}
+pub(crate) struct TokenSet(u128);
 
 impl TokenSet {
-    pub const EMPTY: TokenSet = TokenSet(0);
+    pub const fn empty() -> TokenSet {
+        TokenSet(0)
+    }
+
+    pub const fn singleton(kind: SyntaxKind) -> TokenSet {
+        TokenSet(mask(kind))
+    }
+
+    pub const fn union(self, other: TokenSet) -> TokenSet {
+        TokenSet(self.0 | other.0)
+    }
 
     pub fn contains(&self, kind: SyntaxKind) -> bool {
         self.0 & mask(kind) != 0
     }
 }
 
-#[macro_export]
-macro_rules! token_set {
-    ($($t:ident),*) => { TokenSet($(1u128 << ($t as usize))|*) };
-    ($($t:ident),* ,) => { token_set!($($t),*) };
+const fn mask(kind: SyntaxKind) -> u128 {
+    1u128 << (kind as usize)
 }
 
 #[macro_export]
-macro_rules! token_set_union {
-    ($($ts:expr),*) => { TokenSet($($ts.0)|*) };
-    ($($ts:expr),* ,) => { token_set_union!($($ts),*) };
+macro_rules! token_set {
+    ($($t:ident),*) => { TokenSet::empty()$(.union(TokenSet::singleton($t)))* };
+    ($($t:ident),* ,) => { token_set!($($t),*) };
 }
 
 #[test]