Merge #1393

1393: fix: support existential type r=matklad a=csmoe

Closes https://github.com/rust-analyzer/rust-analyzer/issues/1387
r? @matklad 

Co-authored-by: csmoe <[email protected]>

2 files changed, 17 insertions, 3 deletions

diff --git a/crates/ra_parser/src/grammar/items.rs b/crates/ra_parser/src/grammar/items.rs
index 7718fbe6a..e85147e9e 100644
--- a/crates/ra_parser/src/grammar/items.rs
+++ b/crates/ra_parser/src/grammar/items.rs
@@ -107,6 +107,10 @@ pub(super) fn maybe_item(p: &mut Parser, m: Marker, flavor: ItemFlavor) -> Resul
         p.bump_remap(T![default]);
         has_mods = true;
     }
+    if p.at(IDENT) && p.at_contextual_kw("existential") && p.nth(1) == T![type] {
+        p.bump_remap(T![existential]);
+        has_mods = true;
+    }
 
     // items
     match p.current() {
@@ -165,12 +169,17 @@ pub(super) fn maybe_item(p: &mut Parser, m: Marker, flavor: ItemFlavor) -> Resul
             traits::impl_block(p);
             m.complete(p, IMPL_BLOCK);
         }
+        // test existential_type
+        // existential type Foo: Fn() -> usize;
+        T![type] => {
+            type_def(p, m);
+        }
         _ => {
             if !has_visibility && !has_mods {
                 return Err(m);
             } else {
                 if has_mods {
-                    p.error("expected fn, trait or impl");
+                    p.error("expected existential, fn, trait or impl");
                 } else {
                     p.error("expected an item");
                 }
@@ -187,7 +196,9 @@ fn items_without_modifiers(p: &mut Parser, m: Marker) -> Result<(), Marker> {
         // test extern_crate
         // extern crate foo;
         T![extern] if la == T![crate] => extern_crate_item(p, m),
-        T![type] => type_def(p, m),
+        T![type] => {
+            type_def(p, m);
+        }
         T![mod] => mod_item(p, m),
         T![struct] => {
             // test struct_items
@@ -308,7 +319,6 @@ fn type_def(p: &mut Parser, m: Marker) {
     // test type_item_where_clause
     // type Foo where Foo: Copy = ();
     type_params::opt_where_clause(p);
-
     if p.eat(T![=]) {
         types::type_(p);
     }
diff --git a/crates/ra_parser/src/syntax_kind/generated.rs b/crates/ra_parser/src/syntax_kind/generated.rs
index 2c021f3e9..036415eac 100644
--- a/crates/ra_parser/src/syntax_kind/generated.rs
+++ b/crates/ra_parser/src/syntax_kind/generated.rs
@@ -106,6 +106,7 @@ pub enum SyntaxKind {
     TRY_KW,
     AUTO_KW,
     DEFAULT_KW,
+    EXISTENTIAL_KW,
     UNION_KW,
     INT_NUMBER,
     FLOAT_NUMBER,
@@ -336,6 +337,7 @@ macro_rules! T {
     (try) => { $crate::SyntaxKind::TRY_KW };
     (auto) => { $crate::SyntaxKind::AUTO_KW };
     (default) => { $crate::SyntaxKind::DEFAULT_KW };
+    (existential) => { $crate::SyntaxKind::EXISTENTIAL_KW };
     (union) => { $crate::SyntaxKind::UNION_KW };
 }
 
@@ -394,6 +396,7 @@ impl SyntaxKind {
             | TRY_KW
             | AUTO_KW
             | DEFAULT_KW
+            | EXISTENTIAL_KW
             | UNION_KW
                 => true,
             _ => false
@@ -566,6 +569,7 @@ impl SyntaxKind {
             TRY_KW => &SyntaxInfo { name: "TRY_KW" },
             AUTO_KW => &SyntaxInfo { name: "AUTO_KW" },
             DEFAULT_KW => &SyntaxInfo { name: "DEFAULT_KW" },
+            EXISTENTIAL_KW => &SyntaxInfo { name: "EXISTENTIAL_KW" },
             UNION_KW => &SyntaxInfo { name: "UNION_KW" },
             INT_NUMBER => &SyntaxInfo { name: "INT_NUMBER" },
             FLOAT_NUMBER => &SyntaxInfo { name: "FLOAT_NUMBER" },