10 files changed, 70 insertions, 4 deletions

diff --git a/crates/libsyntax2/src/grammar/expressions/atom.rs b/crates/libsyntax2/src/grammar/expressions/atom.rs
index 417366026..b0e270426 100644
--- a/crates/libsyntax2/src/grammar/expressions/atom.rs
+++ b/crates/libsyntax2/src/grammar/expressions/atom.rs
@@ -13,7 +13,7 @@ use super::*;
 //     let _ = b"e";
 //     let _ = br"f";
 // }
-const LITERAL_FIRST: TokenSet =
+pub(crate) const LITERAL_FIRST: TokenSet =
     token_set![TRUE_KW, FALSE_KW, INT_NUMBER, FLOAT_NUMBER, BYTE, CHAR,
                STRING, RAW_STRING, BYTE_STRING, RAW_BYTE_STRING];
 
diff --git a/crates/libsyntax2/src/grammar/expressions/mod.rs b/crates/libsyntax2/src/grammar/expressions/mod.rs
index e133c1d9b..59a0564d9 100644
--- a/crates/libsyntax2/src/grammar/expressions/mod.rs
+++ b/crates/libsyntax2/src/grammar/expressions/mod.rs
@@ -1,7 +1,7 @@
 mod atom;
 
 use super::*;
-pub(super) use self::atom::literal;
+pub(super) use self::atom::{literal, LITERAL_FIRST};
 
 const EXPR_FIRST: TokenSet = LHS_FIRST;
 
diff --git a/crates/libsyntax2/src/grammar/items/mod.rs b/crates/libsyntax2/src/grammar/items/mod.rs
index d236fb506..206c85280 100644
--- a/crates/libsyntax2/src/grammar/items/mod.rs
+++ b/crates/libsyntax2/src/grammar/items/mod.rs
@@ -250,8 +250,10 @@ fn function(p: &mut Parser, flavor: ItemFlavor) {
 
     // test fn_decl
     // trait T { fn foo(); }
-    if !p.eat(SEMI) {
+    if p.at(L_CURLY) {
         expressions::block(p);
+    } else {
+        p.expect(SEMI);
     }
 }
 
diff --git a/crates/libsyntax2/src/grammar/params.rs b/crates/libsyntax2/src/grammar/params.rs
index 5b1322b3a..bc0cb44ba 100644
--- a/crates/libsyntax2/src/grammar/params.rs
+++ b/crates/libsyntax2/src/grammar/params.rs
@@ -48,6 +48,10 @@ fn list_(p: &mut Parser, flavor: Flavor) {
         opt_self_param(p);
     }
     while !p.at(EOF) && !p.at(ket) {
+        if !VALUE_PARAMETER_FIRST.contains(p.current()) {
+            p.error("expected value parameter");
+            break;
+        }
         value_parameter(p, flavor);
         if !p.at(ket) {
             p.expect(COMMA);
@@ -57,6 +61,13 @@ fn list_(p: &mut Parser, flavor: Flavor) {
     m.complete(p, PARAM_LIST);
 }
 
+
+const VALUE_PARAMETER_FIRST: TokenSet =
+    token_set_union![
+        patterns::PATTERN_FIRST,
+        types::TYPE_FIRST,
+    ];
+
 fn value_parameter(p: &mut Parser, flavor: Flavor) {
     let m = p.start();
     match flavor {
diff --git a/crates/libsyntax2/src/grammar/paths.rs b/crates/libsyntax2/src/grammar/paths.rs
index 8f5e82d91..7c9fb8be2 100644
--- a/crates/libsyntax2/src/grammar/paths.rs
+++ b/crates/libsyntax2/src/grammar/paths.rs
@@ -1,5 +1,8 @@
 use super::*;
 
+pub(super) const PATH_FIRST: TokenSet =
+    token_set![IDENT, SELF_KW, SUPER_KW, COLONCOLON, L_ANGLE];
+
 pub(super) fn is_path_start(p: &Parser) -> bool {
     match p.current() {
         IDENT | SELF_KW | SUPER_KW | COLONCOLON => true,
diff --git a/crates/libsyntax2/src/grammar/patterns.rs b/crates/libsyntax2/src/grammar/patterns.rs
index 7ddbfa318..11852e0d3 100644
--- a/crates/libsyntax2/src/grammar/patterns.rs
+++ b/crates/libsyntax2/src/grammar/patterns.rs
@@ -1,5 +1,12 @@
 use super::*;
 
+pub(super) const PATTERN_FIRST: TokenSet =
+    token_set_union![
+        token_set![REF_KW, MUT_KW, L_PAREN, L_BRACK, AMP],
+        expressions::LITERAL_FIRST,
+        paths::PATH_FIRST,
+    ];
+
 pub(super) fn pattern(p: &mut Parser) {
     if let Some(lhs) = atom_pat(p) {
         // test range_pat
diff --git a/crates/libsyntax2/src/grammar/types.rs b/crates/libsyntax2/src/grammar/types.rs
index 2088a38e3..89030e66c 100644
--- a/crates/libsyntax2/src/grammar/types.rs
+++ b/crates/libsyntax2/src/grammar/types.rs
@@ -1,5 +1,13 @@
 use super::*;
 
+pub(super) const TYPE_FIRST: TokenSet =
+    token_set_union![
+        token_set![
+            L_PAREN, EXCL, STAR, L_BRACK, AMP, UNDERSCORE, FN_KW, UNSAFE_KW, EXTERN_KW, FOR_KW, IMPL_KW, DYN_KW, L_ANGLE,
+        ],
+        paths::PATH_FIRST,
+    ];
+
 pub(super) fn type_(p: &mut Parser) {
     match p.current() {
         L_PAREN => paren_or_tuple_type(p),
diff --git a/crates/libsyntax2/src/lib.rs b/crates/libsyntax2/src/lib.rs
index d3ecbe470..9f9f3ab3a 100644
--- a/crates/libsyntax2/src/lib.rs
+++ b/crates/libsyntax2/src/lib.rs
@@ -58,6 +58,10 @@ pub fn parse(text: &str) -> SyntaxNode {
     res
 }
 
+#[cfg(not(debug_assertions))]
+fn validate_block_structure(_: SyntaxNodeRef) {}
+
+#[cfg(debug_assertions)]
 fn validate_block_structure(root: SyntaxNodeRef) {
     let mut stack = Vec::new();
     for node in algo::walk::preorder(root) {
@@ -67,7 +71,12 @@ fn validate_block_structure(root: SyntaxNodeRef) {
             }
             SyntaxKind::R_CURLY => {
                 if let Some(pair) = stack.pop() {
-                    assert_eq!(node.parent(), pair.parent());
+                    assert_eq!(
+                        node.parent(),
+                        pair.parent(),
+                        "unpaired curleys:\n{}",
+                        utils::dump_tree(root),
+                    );
                     assert!(
                         node.next_sibling().is_none() && pair.prev_sibling().is_none(),
                         "floating curlys at {:?}\nfile:\n{}\nerror:\n{}\n",
diff --git a/crates/libsyntax2/tests/data/parser/err/0015_curly_in_params.rs b/crates/libsyntax2/tests/data/parser/err/0015_curly_in_params.rs
new file mode 100644
index 000000000..156e70251
--- /dev/null
+++ b/crates/libsyntax2/tests/data/parser/err/0015_curly_in_params.rs
@@ -0,0 +1,2 @@
+fn foo(}) {
+}
diff --git a/crates/libsyntax2/tests/data/parser/err/0015_curly_in_params.txt b/crates/libsyntax2/tests/data/parser/err/0015_curly_in_params.txt
new file mode 100644
index 000000000..841379797
--- /dev/null
+++ b/crates/libsyntax2/tests/data/parser/err/0015_curly_in_params.txt
@@ -0,0 +1,24 @@
+FILE@[0; 14)
+  FN_DEF@[0; 7)
+    FN_KW@[0; 2)
+    WHITESPACE@[2; 3)
+    NAME@[3; 6)
+      IDENT@[3; 6) "foo"
+    PARAM_LIST@[6; 7)
+      L_PAREN@[6; 7)
+      err: `expected value parameter`
+      err: `expected R_PAREN`
+      err: `expected SEMI`
+      err: `expected an item`
+  ERROR@[7; 8)
+    R_CURLY@[7; 8)
+    err: `expected an item`
+  ERROR@[8; 9)
+    R_PAREN@[8; 9)
+  WHITESPACE@[9; 10)
+  err: `expected an item`
+  ERROR@[10; 13)
+    L_CURLY@[10; 11)
+    WHITESPACE@[11; 12)
+    R_CURLY@[12; 13)
+  WHITESPACE@[13; 14)