Function to_expression_failed 

pub fn to_expression_failed(err: LanguageError, meta: &EvalMeta) -> CamelError

Map a LanguageError onto CamelError::ExpressionFailed using the trusted route metadata.

The class and position come from the error itself (defaulting to class Runtime, position None when the variant carries none). ConversionError populates conversion; when its target is a generic placeholder (see [GENERIC_TARGETS]) and meta.target is known, the placeholder is rewritten to the trusted destination. Runtime-derived strings (script map keys, exchange header keys) are never written into the ConversionDetail.