fix: improve diagnose for invalid generic function call

Fixes AssemblyScript#2780

Author: HerrCai0907

src/parser.ts

@@ -4278,6 +4278,23 @@ 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)
+          ) {
+            // detect 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;
         }

tests/parser/diagnose-generic.ts

@@ -0,0 +1,9 @@
+true<false>(true);
+a<12345>() => {};
+1 < 2,3,4 > (1,2,3);
+{
+  a<12345>();
+}
+{
+  1 + a<12345>() + 1;
+}

tests/parser/diagnose-generic.ts.fixture.ts

@@ -0,0 +1,7 @@
+true < false > (true);
+a < 12345 > () => {};
+1 < 2,3,4 > (1,2,3);
+{}
+{}
+// ERROR 1110: "Type expected." in diagnose-generic.ts(5,5+5)
+// ERROR 1110: "Type expected." in diagnose-generic.ts(8,9+5)