mozilla/pdf.js · error · FormatError

PostScript function: a procedure block must be followed by '

Error message

PostScript function: a procedure block must be followed by 'if' or '{…} ifelse'.

What it means

Error "PostScript function: a procedure block must be followed by 'if' or '{…} ifelse'." thrown in mozilla/pdf.js.

Source

Thrown at src/core/postscript/ast.js:294

          break;

        case TOKEN.lbrace: {
          // Start of a sub-procedure: must be followed by 'if' or '{ } ifelse'.
          this._advance();
          const thenBlock = this._parseBlock();
          this._expect(TOKEN.rbrace);

          if (this._token.id === TOKEN.if) {
            this._advance();
            instructions.push(new PsIf(thenBlock));
          } else if (this._token.id === TOKEN.lbrace) {
            this._advance();
            const elseBlock = this._parseBlock();
            this._expect(TOKEN.rbrace);
            this._expect(TOKEN.ifelse);
            instructions.push(new PsIfElse(thenBlock, elseBlock));
          } else {
            throw new FormatError(
              "PostScript function: a procedure block must be followed by 'if' or '{…} ifelse'."
            );
          }
          break;
        }

        case TOKEN.rbrace:
        case TOKEN.eof:
          // End of this block; let the caller consume the '}'.
          return new PsBlock(instructions);

        case TOKEN.if:
        case TOKEN.ifelse:
          // 'if'/'ifelse' without a preceding block.
          throw new FormatError(
            `PostScript function: unexpected '${tok.value}' operator.`
          );

View on GitHub (pinned to 5903d58d58)

Solutions

1. In the Type 4 function, follow each procedure block with `if` or use the `{...} {...} ifelse` form; a bare procedure is not allowed.

When it happens

Trigger: Thrown at src/core/postscript/ast.js:294 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of mozilla/pdf.js@5903d58d58 (2026-08-13). Data as JSON: /api/errors/9918dec314ed9301. Report an issue: GitHub.