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]>

7 files changed, 53 insertions, 6 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" },
diff --git a/crates/ra_syntax/src/grammar.ron b/crates/ra_syntax/src/grammar.ron
index 1c2714307..eab55058b 100644
--- a/crates/ra_syntax/src/grammar.ron
+++ b/crates/ra_syntax/src/grammar.ron
@@ -100,6 +100,7 @@ Grammar(
     contextual_keywords: [
         "auto",
         "default",
+        "existential",
         "union",
     ],
     literals: [
diff --git a/crates/ra_syntax/tests/data/parser/err/0011_extern_struct.txt b/crates/ra_syntax/tests/data/parser/err/0011_extern_struct.txt
index 033dac2aa..381147dc0 100644
--- a/crates/ra_syntax/tests/data/parser/err/0011_extern_struct.txt
+++ b/crates/ra_syntax/tests/data/parser/err/0011_extern_struct.txt
@@ -10,4 +10,4 @@ SOURCE_FILE@[0; 19)
       IDENT@[14; 17) "Foo"
     SEMI@[17; 18) ";"
   WHITESPACE@[18; 19) "\n"
-error 6: expected fn, trait or impl
+error 6: expected existential, fn, trait or impl
diff --git a/crates/ra_syntax/tests/data/parser/inline/err/0010_wrong_order_fns.txt b/crates/ra_syntax/tests/data/parser/inline/err/0010_wrong_order_fns.txt
index 9eb4c9b36..b1ef210d3 100644
--- a/crates/ra_syntax/tests/data/parser/inline/err/0010_wrong_order_fns.txt
+++ b/crates/ra_syntax/tests/data/parser/inline/err/0010_wrong_order_fns.txt
@@ -35,5 +35,5 @@ SOURCE_FILE@[0; 50)
       L_CURLY@[47; 48) "{"
       R_CURLY@[48; 49) "}"
   WHITESPACE@[49; 50) "\n"
-error 5: expected fn, trait or impl
-error 31: expected fn, trait or impl
+error 5: expected existential, fn, trait or impl
+error 31: expected existential, fn, trait or impl
diff --git a/crates/ra_syntax/tests/data/parser/inline/ok/0131_existential_type.rs b/crates/ra_syntax/tests/data/parser/inline/ok/0131_existential_type.rs
new file mode 100644
index 000000000..23baf7145
--- /dev/null
+++ b/crates/ra_syntax/tests/data/parser/inline/ok/0131_existential_type.rs
@@ -0,0 +1 @@
+existential type Foo: Fn() -> usize;
diff --git a/crates/ra_syntax/tests/data/parser/inline/ok/0131_existential_type.txt b/crates/ra_syntax/tests/data/parser/inline/ok/0131_existential_type.txt
new file mode 100644
index 000000000..6bfac985a
--- /dev/null
+++ b/crates/ra_syntax/tests/data/parser/inline/ok/0131_existential_type.txt
@@ -0,0 +1,31 @@
+SOURCE_FILE@[0; 37)
+  TYPE_ALIAS_DEF@[0; 36)
+    EXISTENTIAL_KW@[0; 11) "existential"
+    WHITESPACE@[11; 12) " "
+    TYPE_KW@[12; 16) "type"
+    WHITESPACE@[16; 17) " "
+    NAME@[17; 20)
+      IDENT@[17; 20) "Foo"
+    COLON@[20; 21) ":"
+    WHITESPACE@[21; 22) " "
+    TYPE_BOUND_LIST@[22; 35)
+      TYPE_BOUND@[22; 35)
+        PATH_TYPE@[22; 35)
+          PATH@[22; 35)
+            PATH_SEGMENT@[22; 35)
+              NAME_REF@[22; 24)
+                IDENT@[22; 24) "Fn"
+              PARAM_LIST@[24; 26)
+                L_PAREN@[24; 25) "("
+                R_PAREN@[25; 26) ")"
+              WHITESPACE@[26; 27) " "
+              RET_TYPE@[27; 35)
+                THIN_ARROW@[27; 29) "->"
+                WHITESPACE@[29; 30) " "
+                PATH_TYPE@[30; 35)
+                  PATH@[30; 35)
+                    PATH_SEGMENT@[30; 35)
+                      NAME_REF@[30; 35)
+                        IDENT@[30; 35) "usize"
+    SEMI@[35; 36) ";"
+  WHITESPACE@[36; 37) "\n"