16 Errors

This specification specifies the last possible moment an error occurs. A given implementation may generate errors sooner (e.g., at compile-time). Doing so may cause differences in behaviour among implementations. Notably, if runtime errors become catchable in future versions, a given error would not be catchable if an implementation generates the error at compile-time rather than runtime.

An ECMAScript compiler should detect errors at compile time in all code presented to it, even code that detailed analysis might prove to be "dead" (never executed). A programmer should not rely on the trick of placing code within an if (false) statement, for example, to try to suppress compile-time error detection.

In general, if a compiler can prove that a construct cannot execute without error under any circumstances, then it may issue a compile-time error even though the construct might never be executed at all.

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