7 files changed, 92 insertions, 13 deletions

diff --git a/src/parser/grammar/items/traits.rs b/src/parser/grammar/items/traits.rs
index 7fd011ffd..c7450b761 100644
--- a/src/parser/grammar/items/traits.rs
+++ b/src/parser/grammar/items/traits.rs
@@ -14,7 +14,47 @@ pub(super) fn trait_item(p: &mut Parser) {
 pub(super) fn impl_item(p: &mut Parser) {
     assert!(p.at(IMPL_KW));
     p.bump();
-    p.expect(IDENT);
+    if choose_type_params_over_qpath(p) {
+        type_params::list(p);
+    }
+
+    // TODO: never type
+    // impl ! {}
+
+    // test impl_item_neg
+    // impl !Send for X {}
+    p.eat(EXCL);
+    types::type_(p);
+    if p.eat(FOR_KW) {
+        types::type_(p);
+    }
+    type_params::where_clause(p);
     p.expect(L_CURLY);
     p.expect(R_CURLY);
 }
+
+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.
+    // The following combinations can only start generics,
+    // but not qualified paths (with one exception):
+    //     `<` `>` - empty generic parameters
+    //     `<` `#` - generic parameters with attributes
+    //     `<` (LIFETIME|IDENT) `>` - single generic parameter
+    //     `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
+    //     `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
+    //     `<` (LIFETIME|IDENT) `=` - generic parameter with a default
+    // The only truly ambiguous case is
+    //     `<` IDENT `>` `::` IDENT ...
+    // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
+    // because this is what almost always expected in practice, qualified paths in impls
+    // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
+    if !p.at(L_ANGLE) {
+        return false;
+    }
+    if p.nth(1) == POUND || p.nth(1) == R_ANGLE {
+        return true;
+    }
+    (p.nth(1) == LIFETIME || p.nth(1) == IDENT)
+        && (p.nth(2) == R_ANGLE || p.nth(2) == COMMA || p.nth(2) == COLON || p.nth(2) == EQ)
+}
diff --git a/tests/data/parser/inline/0008_unsafe_impl.txt b/tests/data/parser/inline/0008_unsafe_impl.txt
index a88a447cb..d21782b45 100644
--- a/tests/data/parser/inline/0008_unsafe_impl.txt
+++ b/tests/data/parser/inline/0008_unsafe_impl.txt
@@ -3,9 +3,13 @@ FILE@[0; 19)
     UNSAFE_KW@[0; 6)
     WHITESPACE@[6; 7)
     IMPL_KW@[7; 11)
-    WHITESPACE@[11; 12)
-    IDENT@[12; 15) "Foo"
-    WHITESPACE@[15; 16)
+    PATH_TYPE@[11; 16)
+      PATH@[11; 16)
+        PATH_SEGMENT@[11; 16)
+          NAME_REF@[11; 16)
+            WHITESPACE@[11; 12)
+            IDENT@[12; 15) "Foo"
+            WHITESPACE@[15; 16)
     L_CURLY@[16; 17)
     R_CURLY@[17; 18)
     WHITESPACE@[18; 19)
diff --git a/tests/data/parser/inline/0010_unsafe_default_impl.txt b/tests/data/parser/inline/0010_unsafe_default_impl.txt
index 7450381cb..a89008c8a 100644
--- a/tests/data/parser/inline/0010_unsafe_default_impl.txt
+++ b/tests/data/parser/inline/0010_unsafe_default_impl.txt
@@ -5,9 +5,13 @@ FILE@[0; 27)
     DEFAULT_KW@[7; 14)
     WHITESPACE@[14; 15)
     IMPL_KW@[15; 19)
-    WHITESPACE@[19; 20)
-    IDENT@[20; 23) "Foo"
-    WHITESPACE@[23; 24)
+    PATH_TYPE@[19; 24)
+      PATH@[19; 24)
+        PATH_SEGMENT@[19; 24)
+          NAME_REF@[19; 24)
+            WHITESPACE@[19; 20)
+            IDENT@[20; 23) "Foo"
+            WHITESPACE@[23; 24)
     L_CURLY@[24; 25)
     R_CURLY@[25; 26)
     WHITESPACE@[26; 27)
diff --git a/tests/data/parser/inline/0046_default_impl.txt b/tests/data/parser/inline/0046_default_impl.txt
index bc17bcaff..3718aea3b 100644
--- a/tests/data/parser/inline/0046_default_impl.txt
+++ b/tests/data/parser/inline/0046_default_impl.txt
@@ -3,9 +3,13 @@ FILE@[0; 20)
     DEFAULT_KW@[0; 7)
     WHITESPACE@[7; 8)
     IMPL_KW@[8; 12)
-    WHITESPACE@[12; 13)
-    IDENT@[13; 16) "Foo"
-    WHITESPACE@[16; 17)
+    PATH_TYPE@[12; 17)
+      PATH@[12; 17)
+        PATH_SEGMENT@[12; 17)
+          NAME_REF@[12; 17)
+            WHITESPACE@[12; 13)
+            IDENT@[13; 16) "Foo"
+            WHITESPACE@[16; 17)
     L_CURLY@[17; 18)
     R_CURLY@[18; 19)
     WHITESPACE@[19; 20)
diff --git a/tests/data/parser/inline/0047_impl_item.txt b/tests/data/parser/inline/0047_impl_item.txt
index a7f3155e1..90f11e8a2 100644
--- a/tests/data/parser/inline/0047_impl_item.txt
+++ b/tests/data/parser/inline/0047_impl_item.txt
@@ -1,9 +1,13 @@
 FILE@[0; 12)
   IMPL_ITEM@[0; 12)
     IMPL_KW@[0; 4)
-    WHITESPACE@[4; 5)
-    IDENT@[5; 8) "Foo"
-    WHITESPACE@[8; 9)
+    PATH_TYPE@[4; 9)
+      PATH@[4; 9)
+        PATH_SEGMENT@[4; 9)
+          NAME_REF@[4; 9)
+            WHITESPACE@[4; 5)
+            IDENT@[5; 8) "Foo"
+            WHITESPACE@[8; 9)
     L_CURLY@[9; 10)
     R_CURLY@[10; 11)
     WHITESPACE@[11; 12)
diff --git a/tests/data/parser/inline/0048_impl_item_neg.rs b/tests/data/parser/inline/0048_impl_item_neg.rs
new file mode 100644
index 000000000..b7527c870
--- /dev/null
+++ b/tests/data/parser/inline/0048_impl_item_neg.rs
@@ -0,0 +1 @@
+impl !Send for X {}
diff --git a/tests/data/parser/inline/0048_impl_item_neg.txt b/tests/data/parser/inline/0048_impl_item_neg.txt
new file mode 100644
index 000000000..1b7581434
--- /dev/null
+++ b/tests/data/parser/inline/0048_impl_item_neg.txt
@@ -0,0 +1,22 @@
+FILE@[0; 20)
+  IMPL_ITEM@[0; 20)
+    IMPL_KW@[0; 4)
+    WHITESPACE@[4; 5)
+    EXCL@[5; 6)
+    PATH_TYPE@[6; 11)
+      PATH@[6; 11)
+        PATH_SEGMENT@[6; 11)
+          NAME_REF@[6; 11)
+            IDENT@[6; 10) "Send"
+            WHITESPACE@[10; 11)
+    FOR_KW@[11; 14)
+    PATH_TYPE@[14; 17)
+      PATH@[14; 17)
+        PATH_SEGMENT@[14; 17)
+          NAME_REF@[14; 17)
+            WHITESPACE@[14; 15)
+            IDENT@[15; 16) "X"
+            WHITESPACE@[16; 17)
+    L_CURLY@[17; 18)
+    R_CURLY@[18; 19)
+    WHITESPACE@[19; 20)