From 341def6bd78cca63b729d56027e1598eef1e2bc8 Mon Sep 17 00:00:00 2001
From: Congcong Cai <congcong.cai@bmw.com>
Date: Mon, 6 Nov 2023 15:11:59 +0800
Subject: [PATCH] fix: improve diagnose for invalid generic function call

Fixes #2780
---
 src/parser.ts                               | 18 ++++++++++++++++++
 tests/parser/diagnose-generic.ts            | 10 ++++++++++
 tests/parser/diagnose-generic.ts.fixture.ts |  8 ++++++++
 3 files changed, 36 insertions(+)
 create mode 100644 tests/parser/diagnose-generic.ts
 create mode 100644 tests/parser/diagnose-generic.ts.fixture.ts

diff --git a/src/parser.ts b/src/parser.ts
index 58050e837e..81e83e3f88 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -4278,6 +4278,24 @@ export class Parser extends DiagnosticEmitter {
         case Token.In: {
           let next = this.parseExpression(tn, nextPrecedence + 1);
           if (!next) return null;
+          let state = tn.mark();
+          if (
+            expr.kind != NodeKind.Literal &&
+            token == Token.LessThan &&
+            tn.skip(Token.GreaterThan) &&
+            tn.skip(Token.OpenParen) &&
+            tn.skip(Token.CloseParen) &&
+            !(tn.skip(Token.Equals_GreaterThan) || tn.skip(Token.Colon))
+          ) {
+            // detect Expr '<' Expr '>' '(' ')'
+            //   except Expr '<' Expr '>' '(' ')' '=>'
+            //   except Expr '<' Expr '>' '(' ')' ':'
+            this.error(DiagnosticCode.Type_expected, next.range);
+            tn.discard(state);
+            return null;
+          }
+          tn.reset(state);
+          tn.discard(state);
           expr = Node.createBinaryExpression(token, expr, next, tn.range(startPos, tn.pos));
           break;
         }
diff --git a/tests/parser/diagnose-generic.ts b/tests/parser/diagnose-generic.ts
new file mode 100644
index 0000000000..66fd949457
--- /dev/null
+++ b/tests/parser/diagnose-generic.ts
@@ -0,0 +1,10 @@
+true<false>(true);
+a<12345>() => {};
+a<12345>() : void => {};
+1 < 2,3,4 > (1,2,3);
+{
+  a<12345>();
+}
+{
+  1 + a<12345>() + 1;
+}
diff --git a/tests/parser/diagnose-generic.ts.fixture.ts b/tests/parser/diagnose-generic.ts.fixture.ts
new file mode 100644
index 0000000000..e2c0bf6eb7
--- /dev/null
+++ b/tests/parser/diagnose-generic.ts.fixture.ts
@@ -0,0 +1,8 @@
+true < false > (true);
+a < 12345 > () => {};
+a < 12345 > (): void => {};
+1 < 2,3,4 > (1,2,3);
+{}
+{}
+// ERROR 1110: "Type expected." in diagnose-generic.ts(6,5+5)
+// ERROR 1110: "Type expected." in diagnose-generic.ts(9,9+5)