Editorial: Correct usage of 'Let'/'Set' in algorithms

[kimjg1119]

There are some algorithms where same variable is defined twice:

• 15.10.2 Static Semantics: HasCallInTailPosition
• 15.5.5 Runtime Semantics: Evaluation

Both algorithms define a (target) variable at the beginning, thus the declarations afterward are redeclaration which should be fixed.

Please note that this is a continuation of PR #2365.

HasCallInTailPosition, CaseBlock

1. Let _has_ be *false*.
2. If the first |CaseClauses| is present, let _has_ be HasCallInTailPosition of the first |CaseClauses| with argument _call_.
3. If _has_ is *true*, return *true*.
4. Let _has_ be HasCallInTailPosition of |DefaultClause| with argument _call_.
5. If _has_ is *true*, return *true*.
6. If the second |CaseClauses| is present, let _has_ be HasCallInTailPosition of the second |CaseClauses| with argument _call_.
7. Return _has_.

The variable has is defined in step 1. However, in steps 2, 4, and 6, there may be duplication since let is used to modify the value instead of set.

Evaluation, YieldExpression

1. Let _generatorKind_ be GetGeneratorKind().
2. Let _exprRef_ be ? Evaluation of |AssignmentExpression|.
3. Let _value_ be ? GetValue(_exprRef_).
...
7. Repeat,
  a. If _received_.[[Type]] is ~normal~, then
    ...
  b. Else if _received_.[[Type]] is ~throw~, then
    ...
  c. Else,
    i. Assert: _received_.[[Type]] is ~return~. 
    ii. Let _return_ be ? GetMethod(_iterator_, *"return"*).
    iii. If _return_ is *undefined*, then
      1. Let _value_ be _received_.[[Value]].
      2. If _generatorKind_ is ~async~, then
        a. Set _value_ to ? Await(_value_).
      3. Return Completion Record { [[Type]]: ~return~, [[Value]]: _value_, [[Target]]: ~empty~ }.
    ...
    viii. If _done_ is *true*, then
      1. Let _value_ be ? IteratorValue(_innerReturnResult_).
      2. Return Completion Record { [[Type]]: ~return~, [[Value]]: _value_, [[Target]]: ~empty~ }.
    ix. If _generatorKind_ is ~async~, set _received_ to Completion(AsyncGeneratorYield(? IteratorValue(_innerReturnResult_))).
    x. Else, set _received_ to Completion(GeneratorYield(_innerReturnResult_)).

The variable value is defined in step 3. However, in step 7.c.iii.1, value may be redefined since the spec uses Let to change the value, rather than Set. This potential redefinition may also occur in step 7.c.viii.1.

[ljharb]

@kimjg1119 would you please register as a contributor?

[kimjg1119]

@kimjg1119 would you please register as a contributor?

Submitted. Thank you for letting me know!