9 files changed, 213 insertions, 15 deletions

diff --git a/crates/libsyntax2/src/grammar/paths.rs b/crates/libsyntax2/src/grammar/paths.rs
index c277e2a6b..aa5ecf4b8 100644
--- a/crates/libsyntax2/src/grammar/paths.rs
+++ b/crates/libsyntax2/src/grammar/paths.rs
@@ -62,7 +62,7 @@ fn path_segment(p: &mut Parser, mode: Mode, first: bool) {
         }
         SELF_KW | SUPER_KW => p.bump(),
         _ => {
-            p.error("expected identifier");
+            p.err_and_bump("expected identifier");
         }
     };
     segment.complete(p, PATH_SEGMENT);
diff --git a/crates/libsyntax2/src/grammar/patterns.rs b/crates/libsyntax2/src/grammar/patterns.rs
index 436f3b26d..220f36db7 100644
--- a/crates/libsyntax2/src/grammar/patterns.rs
+++ b/crates/libsyntax2/src/grammar/patterns.rs
@@ -60,6 +60,7 @@ fn atom_pat(p: &mut Parser) -> Option<CompletedMarker> {
 //     let Bar(..) = ();
 // }
 fn path_pat(p: &mut Parser) -> CompletedMarker {
+    assert!(paths::is_path_start(p));
     let m = p.start();
     paths::expr_path(p);
     let kind = match p.current() {
@@ -116,8 +117,11 @@ fn struct_pat_fields(p: &mut Parser) {
                 p.bump();
                 pattern(p);
             }
-            _ => {
+            REF_KW | MUT_KW | IDENT => {
                 bind_pat(p, false);
+            },
+            _ => {
+                p.err_and_bump("expected ident");
             }
         }
         if !p.at(R_CURLY) {
diff --git a/crates/libsyntax2/src/grammar/type_params.rs b/crates/libsyntax2/src/grammar/type_params.rs
index 0a3e8fd07..32b69dc5b 100644
--- a/crates/libsyntax2/src/grammar/type_params.rs
+++ b/crates/libsyntax2/src/grammar/type_params.rs
@@ -121,7 +121,12 @@ fn where_predicate(p: &mut Parser) {
         lifetime_bounds(p)
     } else {
         types::path_type(p);
-        bounds(p);
+        if p.at(COLON) {
+            bounds(p);
+        } else {
+            p.error("expected colon")
+        }
+
     }
     m.complete(p, WHERE_PRED);
 }
diff --git a/crates/libsyntax2/src/grammar/types.rs b/crates/libsyntax2/src/grammar/types.rs
index 5ba3fcca0..88631fefe 100644
--- a/crates/libsyntax2/src/grammar/types.rs
+++ b/crates/libsyntax2/src/grammar/types.rs
@@ -166,8 +166,11 @@ fn fn_pointer_type(p: &mut Parser) {
         p.error("expected `fn`");
         return;
     }
-
-    params::param_list_opt_patterns(p);
+    if p.at(L_PAREN) {
+        params::param_list_opt_patterns(p);
+    } else {
+        p.error("expected parameters")
+    }
     // test fn_pointer_type_with_ret
     // type F = fn() -> ();
     fn_ret_type(p);
diff --git a/crates/libsyntax2/tests/data/parser/err/0004_use_path_bad_segment.txt b/crates/libsyntax2/tests/data/parser/err/0004_use_path_bad_segment.txt
index c6ae68103..64aa07801 100644
--- a/crates/libsyntax2/tests/data/parser/err/0004_use_path_bad_segment.txt
+++ b/crates/libsyntax2/tests/data/parser/err/0004_use_path_bad_segment.txt
@@ -1,20 +1,16 @@
 FILE@[0; 12)
-  USE_ITEM@[0; 9)
+  USE_ITEM@[0; 12)
     USE_KW@[0; 3)
     WHITESPACE@[3; 4)
-    USE_TREE@[4; 9)
-      PATH@[4; 9)
+    USE_TREE@[4; 11)
+      PATH@[4; 11)
         PATH@[4; 7)
           PATH_SEGMENT@[4; 7)
             NAME_REF@[4; 7)
               IDENT@[4; 7) "foo"
         COLONCOLON@[7; 9)
         err: `expected identifier`
-        err: `expected SEMI`
-        err: `expected an item`
-        PATH_SEGMENT@[9; 9)
-  ERROR@[9; 11)
-    INT_NUMBER@[9; 11) "92"
-    err: `expected an item`
-  ERROR@[11; 12)
+        PATH_SEGMENT@[9; 11)
+          ERROR@[9; 11)
+            INT_NUMBER@[9; 11) "92"
     SEMI@[11; 12)
diff --git a/crates/libsyntax2/tests/data/parser/err/0014_where_no_bounds.rs b/crates/libsyntax2/tests/data/parser/err/0014_where_no_bounds.rs
new file mode 100644
index 000000000..75c1d2f98
--- /dev/null
+++ b/crates/libsyntax2/tests/data/parser/err/0014_where_no_bounds.rs
@@ -0,0 +1 @@
+fn foo<T>() where T {}
diff --git a/crates/libsyntax2/tests/data/parser/err/0014_where_no_bounds.txt b/crates/libsyntax2/tests/data/parser/err/0014_where_no_bounds.txt
new file mode 100644
index 000000000..61444a88d
--- /dev/null
+++ b/crates/libsyntax2/tests/data/parser/err/0014_where_no_bounds.txt
@@ -0,0 +1,31 @@
+FILE@[0; 23)
+  FUNCTION@[0; 22)
+    FN_KW@[0; 2)
+    WHITESPACE@[2; 3)
+    NAME@[3; 6)
+      IDENT@[3; 6) "foo"
+    TYPE_PARAM_LIST@[6; 9)
+      L_ANGLE@[6; 7)
+      TYPE_PARAM@[7; 8)
+        NAME@[7; 8)
+          IDENT@[7; 8) "T"
+      R_ANGLE@[8; 9)
+    PARAM_LIST@[9; 11)
+      L_PAREN@[9; 10)
+      R_PAREN@[10; 11)
+    WHITESPACE@[11; 12)
+    WHERE_CLAUSE@[12; 19)
+      WHERE_KW@[12; 17)
+      WHITESPACE@[17; 18)
+      WHERE_PRED@[18; 19)
+        PATH_TYPE@[18; 19)
+          PATH@[18; 19)
+            PATH_SEGMENT@[18; 19)
+              NAME_REF@[18; 19)
+                IDENT@[18; 19) "T"
+                err: `expected colon`
+    WHITESPACE@[19; 20)
+    BLOCK_EXPR@[20; 22)
+      L_CURLY@[20; 21)
+      R_CURLY@[21; 22)
+  WHITESPACE@[22; 23)
diff --git a/crates/libsyntax2/tests/data/parser/ok/0030_traits.rs b/crates/libsyntax2/tests/data/parser/ok/0030_traits.rs
new file mode 100644
index 000000000..23c4be0e1
--- /dev/null
+++ b/crates/libsyntax2/tests/data/parser/ok/0030_traits.rs
@@ -0,0 +1,11 @@
+pub trait WriteMessage {
+    fn write_message(&FrontendMessage);
+}
+
+trait Runnable {
+    fn handler();
+}
+
+trait TraitWithExpr {
+    fn fn_with_expr(x: [i32; 1]);
+}
diff --git a/crates/libsyntax2/tests/data/parser/ok/0030_traits.txt b/crates/libsyntax2/tests/data/parser/ok/0030_traits.txt
new file mode 100644
index 000000000..8abcb01e0
--- /dev/null
+++ b/crates/libsyntax2/tests/data/parser/ok/0030_traits.txt
@@ -0,0 +1,147 @@
+FILE@[0; 164)
+  TRAIT@[0; 164)
+    VISIBILITY@[0; 3)
+      PUB_KW@[0; 3)
+    WHITESPACE@[3; 4)
+    TRAIT_KW@[4; 9)
+    WHITESPACE@[9; 10)
+    NAME@[10; 22)
+      IDENT@[10; 22) "WriteMessage"
+    WHITESPACE@[22; 23)
+    L_CURLY@[23; 24)
+    WHITESPACE@[24; 29)
+    FUNCTION@[29; 164)
+      FN_KW@[29; 31)
+      WHITESPACE@[31; 32)
+      NAME@[32; 45)
+        IDENT@[32; 45) "write_message"
+      PARAM_LIST@[45; 164)
+        L_PAREN@[45; 46)
+        PARAM@[46; 63)
+          REF_PAT@[46; 62)
+            AMP@[46; 47)
+            BIND_PAT@[47; 62)
+              NAME@[47; 62)
+                IDENT@[47; 62) "FrontendMessage"
+                err: `expected COLON`
+                err: `expected type`
+          ERROR@[62; 63)
+            R_PAREN@[62; 63)
+            err: `expected COMMA`
+            err: `expected pattern`
+        PARAM@[63; 66)
+          ERROR@[63; 64)
+            SEMI@[63; 64)
+            err: `expected COLON`
+          WHITESPACE@[64; 65)
+          err: `expected type`
+          ERROR@[65; 66)
+            R_CURLY@[65; 66)
+            err: `expected COMMA`
+        WHITESPACE@[66; 68)
+        err: `expected pattern`
+        PARAM@[68; 82)
+          ERROR@[68; 73)
+            TRAIT_KW@[68; 73)
+            err: `expected COLON`
+          WHITESPACE@[73; 74)
+          PATH_TYPE@[74; 82)
+            PATH@[74; 82)
+              PATH_SEGMENT@[74; 82)
+                NAME_REF@[74; 82)
+                  IDENT@[74; 82) "Runnable"
+                  err: `expected COMMA`
+        WHITESPACE@[82; 83)
+        err: `expected pattern`
+        PARAM@[83; 91)
+          ERROR@[83; 84)
+            L_CURLY@[83; 84)
+            err: `expected COLON`
+          WHITESPACE@[84; 89)
+          FN_POINTER_TYPE@[89; 91)
+            FN_KW@[89; 91)
+            err: `expected parameters`
+            err: `expected COMMA`
+        WHITESPACE@[91; 92)
+        PARAM@[92; 102)
+          TUPLE_STRUCT_PAT@[92; 101)
+            PATH@[92; 99)
+              PATH_SEGMENT@[92; 99)
+                NAME_REF@[92; 99)
+                  IDENT@[92; 99) "handler"
+            L_PAREN@[99; 100)
+            R_PAREN@[100; 101)
+            err: `expected COLON`
+            err: `expected type`
+          ERROR@[101; 102)
+            SEMI@[101; 102)
+            err: `expected COMMA`
+        WHITESPACE@[102; 103)
+        err: `expected pattern`
+        PARAM@[103; 111)
+          ERROR@[103; 104)
+            R_CURLY@[103; 104)
+            err: `expected COLON`
+          WHITESPACE@[104; 106)
+          err: `expected type`
+          ERROR@[106; 111)
+            TRAIT_KW@[106; 111)
+            err: `expected COMMA`
+        WHITESPACE@[111; 112)
+        PARAM@[112; 164)
+          STRUCT_PAT@[112; 163)
+            PATH@[112; 125)
+              PATH_SEGMENT@[112; 125)
+                NAME_REF@[112; 125)
+                  IDENT@[112; 125) "TraitWithExpr"
+            WHITESPACE@[125; 126)
+            L_CURLY@[126; 127)
+            WHITESPACE@[127; 132)
+            err: `expected ident`
+            ERROR@[132; 134)
+              FN_KW@[132; 134)
+              err: `expected COMMA`
+            WHITESPACE@[134; 135)
+            BIND_PAT@[135; 147)
+              NAME@[135; 147)
+                IDENT@[135; 147) "fn_with_expr"
+                err: `expected COMMA`
+                err: `expected ident`
+            ERROR@[147; 148)
+              L_PAREN@[147; 148)
+              err: `expected COMMA`
+            IDENT@[148; 149) "x"
+            COLON@[149; 150)
+            WHITESPACE@[150; 151)
+            SLICE_PAT@[151; 159)
+              L_BRACK@[151; 152)
+              BIND_PAT@[152; 155)
+                NAME@[152; 155)
+                  IDENT@[152; 155) "i32"
+                  err: `expected COMMA`
+                  err: `expected pattern`
+              ERROR@[155; 156)
+                SEMI@[155; 156)
+                err: `expected COMMA`
+              WHITESPACE@[156; 157)
+              LITERAL@[157; 158)
+                INT_NUMBER@[157; 158) "1"
+              R_BRACK@[158; 159)
+              err: `expected COMMA`
+              err: `expected ident`
+            ERROR@[159; 160)
+              R_PAREN@[159; 160)
+              err: `expected COMMA`
+              err: `expected ident`
+            ERROR@[160; 161)
+              SEMI@[160; 161)
+            WHITESPACE@[161; 162)
+            R_CURLY@[162; 163)
+            err: `expected COLON`
+          WHITESPACE@[163; 164)
+          err: `expected type`
+          err: `expected COMMA`
+          err: `expected R_PAREN`
+          err: `expected block`
+          err: `expected R_CURLY`
+          ERROR@[164; 164)