'let' should not be allowed to be bound as a variable in a for-of loop or let/const decl

[DanielRosenwasser]

The following examples should trigger an early error in JS:

let let = 10;

const let = 10;

_{Note: a similar test exists in tests/cases/conformance/es6/for-ofStatements/for-of56.ts) for the following 3 examples}

for (var let of [1,2,3]) {
}

for (let let of [1,2,3]) {
}

for (const let of [1,2,3]) {
}

I'm not sure if the following should trigger an error:

var let = 10;
for (let of [1,2,3]) {
}

---

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13.2.1.1 Static Semantics: Early Errors

LexicalDeclaration : LetOrConst BindingList ;

• It is a Syntax Error if the BoundNames of BindingList contains "let".

---

13.6.4.1 Static Semantics: Early Errors

IterationStatement :

for ( ForDeclaration in Expression ) Statement

for ( ForDeclaration of AssignmentExpression ) Statement

• It is a Syntax Error if the BoundNames of ForDeclaration contains "let".

[yuit]

var let = 10;
for (let of [1,2,3]) {
}

This should trigger an early error from this grammar production

for ( [lookahead ≠ let ] LeftHandSideExpression[?Yield] of AssignmentExpression[In, ?Yield] ) 

[DanielRosenwasser]

Yup - it would be useful to have a test like

var let: number[] = []
let i = false
let s = 0
for (let[i] of [[1],[2],[3],[4],[5]]) {
    s += i
}

As well as one like this:

var let: number[] = []
let i = 0
let s = 0
for ((let[i]) of [1,2,3,4,5]) {
    s += let[i]
    i++
}

Neither of these should error.

[DanielRosenwasser]

💯