fix unexpected eof

+ unexpected eof handled

src/frontend/parser.ts

@@ -28,6 +28,8 @@ import { Position, Token, TokenType } from "./types";
  */
 export default class Parser {
   private tokens: Token[] = [];
+  private endTagStart?: Position;
+  private endTagEnd?: Position;
 
   /**
    * Determines if the parsing is complete and the EOF was reached.
@@ -206,6 +208,10 @@ export default class Parser {
     // Remove <trans> and </trans>, restore EOF
     this.tokens.shift();
     const last = this.tokens.pop() as Token;
+    if(last.type === TokenType.CloseTransTag) {
+      this.endTagStart = last.begin;
+      this.endTagEnd = last.end;
+    }
     this.tokens.push(new Token("EndOfFile", TokenType.EOF, last.end, last.end));
     return result;
   }
@@ -647,6 +653,10 @@ export default class Parser {
       case TokenType.SingleQuoteString:
       case TokenType.DoubleQuoteString:
         return new StringLiteral(this.consume());
+      case TokenType.EOF:
+        const start = this.endTagStart ?? tk.begin;
+        const end = this.endTagEnd ?? tk.end;
+        return new InvalidExpr("EOF", "Expected expression before the end of script.", start, end);
       default:
         // consume the token to prevent infinite loops
         const unk = this.consume();

test.jb

@@ -1,13 +1,3 @@
 <trans>
-  // user-defined system variable
-  someFlag = true;
-  $myGlobalVar = 'someFlag: ' + someFlag;
-  WriteToOperationLog($myGlobalVar);
-  if(someFlag,
-    $myGlobalVar = 'something',
-    $myGlobalVar = 'something else'
-  );
-  // assignment of an unknown token
-  $bad = 5345bnj435;
-  #x
+  x +
 </trans>

tests/typechecker/errors.test.ts

@@ -262,4 +262,12 @@ msg = Case(
     // Local variable 'x' hasn't been initialized
     expect(result.diagnostics[4].error).toStrictEqual(true);
   });
+
+  test('Missing RHS at the EOF.', function() {
+    const script = `<trans>x + </trans>`;
+    const result = typecheck(script);
+    expect(result.diagnostics.length).toStrictEqual(1);
+    // Expected expression before the end of script.
+    expect(result.diagnostics[0].error).toStrictEqual(true);
+  });
 });