|MethodDefinition| is defined in
In certain contexts, |ObjectLiteral| is used as a cover grammar for a more restricted secondary grammar. The |CoverInitializedName| production is necessary to fully cover these secondary grammars. However, use of this production results in an early Syntax Error in normal contexts where an actual |ObjectLiteral| is expected.
-For example, consider:
-
- let o = {f = 1};
- `{f = 1}` is parsed as an |ObjectLiteral| with a |CoverInitializedName|, which results in a Syntax Error via one of the early error rules in the next section.
-In contrast, consider:
-
- ({f = 1} = {f: 2});
- Here, `{f = 1}` is again initially parsed as an |ObjectLiteral| with a |CoverInitializedName|, but since it's the |LeftHandSideExpression| of an |AssignmentExpression|, it must cover an |AssignmentPattern|, so the |ObjectLiteral| and |CoverInitializedName| are not subject to early error rules. Instead, `{f = 1}` is reparsed as an |ObjectAssignmentPattern| with an |AssignmentProperty|, and there is no Syntax Error.
+See the next section for the significance of |CoverInitializedName|.
This production exists so that |ObjectLiteral| can serve as a cover grammar for |ObjectAssignmentPattern|. It cannot occur in an actual object initializer.
+Elsewhere in this specification, there are early error rules that, under certain circumstances, require that a |LeftHandSideExpression| must cover an |AssignmentPattern|. Consequently, |ObjectLiteral| serves as a cover grammar for |ObjectAssignmentPattern|. The |CoverInitializedName| production is necessary to fully cover |AssignmentProperty|, but is not valid within an actual object initializer.
+Specifically, in a context where an actual |ObjectLiteral| is expected, the above early error rule prevents the use of |CoverInitializedName|. But in cases where |ObjectLiteral| is used as a cover grammar, the semantics of "must cover" state that the Parse Nodes within the |ObjectLiteral| are not subject to early error rules, and so |CoverInitializedName| is allowed.
+For example, consider:
+
+ let o = {f = 1};
+ `{f = 1}` is parsed as an |ObjectLiteral| with a |CoverInitializedName|, which results in a Syntax Error via this early error rule.
+In contrast, consider:
+
+ ({f = 1} = {f: 2});
+ Here, `{f = 1}` is again initially parsed as an |ObjectLiteral| with a |CoverInitializedName|, but since it's the |LeftHandSideExpression| of an |AssignmentExpression|, it must cover an |AssignmentPattern|, so the |ObjectLiteral| and |CoverInitializedName| are not subject to early error rules. Instead, `{f = 1}` is reparsed as an |ObjectAssignmentPattern| with an |AssignmentProperty|, and there is no Syntax Error.