Improve const generics parsing

- Handle const generics type args
- Fix issue with const generic as first parameter in trait impl

3 files changed, 14 insertions, 2 deletions

diff --git a/crates/ra_parser/src/grammar/items/traits.rs b/crates/ra_parser/src/grammar/items/traits.rs
index 2c560e824..964fd3041 100644
--- a/crates/ra_parser/src/grammar/items/traits.rs
+++ b/crates/ra_parser/src/grammar/items/traits.rs
@@ -100,6 +100,8 @@ pub(crate) fn impl_item_list(p: &mut Parser) {
     m.complete(p, ITEM_LIST);
 }
 
+// test impl_type_params
+// impl<const N: u32> Bar<N> {}
 fn choose_type_params_over_qpath(p: &Parser) -> bool {
     // There's an ambiguity between generic parameters and qualified paths in impls.
     // If we see `<` it may start both, so we have to inspect some following tokens.
@@ -107,6 +109,7 @@ fn choose_type_params_over_qpath(p: &Parser) -> bool {
     // but not qualified paths (with one exception):
     //     `<` `>` - empty generic parameters
     //     `<` `#` - generic parameters with attributes
+    //     `<` `const` - const generic parameters
     //     `<` (LIFETIME|IDENT) `>` - single generic parameter
     //     `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
     //     `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
@@ -119,7 +122,7 @@ fn choose_type_params_over_qpath(p: &Parser) -> bool {
     if !p.at(T![<]) {
         return false;
     }
-    if p.nth(1) == T![#] || p.nth(1) == T![>] {
+    if p.nth(1) == T![#] || p.nth(1) == T![>] || p.nth(1) == CONST_KW {
         return true;
     }
     (p.nth(1) == LIFETIME || p.nth(1) == IDENT)
diff --git a/crates/ra_parser/src/grammar/type_args.rs b/crates/ra_parser/src/grammar/type_args.rs
index 7256c2697..33d9973e9 100644
--- a/crates/ra_parser/src/grammar/type_args.rs
+++ b/crates/ra_parser/src/grammar/type_args.rs
@@ -26,7 +26,7 @@ pub(super) fn opt_type_arg_list(p: &mut Parser, colon_colon_required: bool) {
 }
 
 // test type_arg
-// type A = B<'static, i32, Item=u64>;
+// type A = B<'static, i32, 1, { 2 }, Item=u64>;
 fn type_arg(p: &mut Parser) {
     let m = p.start();
     match p.current() {
@@ -47,6 +47,14 @@ fn type_arg(p: &mut Parser) {
             types::type_(p);
             m.complete(p, ASSOC_TYPE_ARG);
         }
+        T!['{'] => {
+            expressions::block(p);
+            m.complete(p, CONST_ARG);
+        }
+        k if k.is_literal() => {
+            p.bump(k);
+            m.complete(p, CONST_ARG);
+        }
         _ => {
             types::type_(p);
             m.complete(p, TYPE_ARG);
diff --git a/crates/ra_parser/src/syntax_kind/generated.rs b/crates/ra_parser/src/syntax_kind/generated.rs
index 262c545e4..4b301d67a 100644
--- a/crates/ra_parser/src/syntax_kind/generated.rs
+++ b/crates/ra_parser/src/syntax_kind/generated.rs
@@ -234,6 +234,7 @@ pub enum SyntaxKind {
     LIFETIME_ARG,
     TYPE_ARG,
     ASSOC_TYPE_ARG,
+    CONST_ARG,
     PARAM_LIST,
     PARAM,
     SELF_PARAM,