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'DO' expected

Velox reports 'DO' expected after the controlling part of a for, while or with statement when the required do keyword is absent.

Required forms​

for Index := First to Last do
  Statement;

while Condition do
  Statement;

with RecordOrObject do
  Statement;

A repeat ... until Condition loop does not use do.

Example​

procedure ScriptEvent(var Value: Variant);
var
  Index: Integer;
begin
  for Index := 1 to 3 // Error: 'DO' expected
    Value := Index;
end;

Add the keyword between the loop range and body:

for Index := 1 to 3 do
  Value := Index;

Use a compound statement when the body contains several statements:

while HasMore do
begin
  ReadNext;
  ProcessCurrent;
end;

How Velox detects it​

The modified PascalScript compiler emits ecDoExpected in ProcessFor, ProcessWhile and ProcessWith after their control expression has been parsed. Velox reports the current token where do should have appeared.

If the control expression is incomplete, the highlighted first body token may be a consequence rather than the root cause. Check missing parentheses, the to/downto keyword and the loop-control assignment before inserting do mechanically.

Common causes​

  • Omitting do after a for range or while condition.
  • Writing then, copied from an if statement.
  • Adding do to a repeat loop and thereby shifting later parsing.
  • Starting the loop body before completing the condition.
  • Forgetting do after a with expression because it is not visually a loop.

Correction procedure​

  1. Identify the owning for, while or with keyword.
  2. Complete its control clause first.
  3. Add exactly one do before the body statement.
  4. Wrap a multi-statement body in begin..end.
  5. Recompile and resolve the earliest remaining structural diagnostic.
  • for loop — :=, to/downto and counter behaviour.
  • while loop — pre-test condition behaviour.
  • repeat loop — the loop form that does not use do.
  • with — record/class member context.

External references​