2.1.16 [ECMA-262/6] Section 12.4.1 Static Semantics: Early Errors

V0045: Postfix increment or decrement gives an early Syntax Error if applied to an immutable binding

The specification states:

 12.4.1 Static Semantics: Early Errors
         PostfixExpression :
             LeftHandSideExpression ++
             LeftHandSideExpression --
     • It is an early Reference Error if IsValidSimpleAssignmentTarget of 
     LeftHandSideExpression is false.

IE11 Mode (All versions)

It is an early SyntaxError if LeftHandSideExpression is an immutable binding reference (i.e. a const declared variable).