Macro impl_supports_fn 

impl_supports_fn!() { /* proc-macro */ }

Implement a built-in SQL function support marker for specific argument counts.

This macro is intended for custom drivers to opt into the built-in SQL functions that query!/query_lazy! validate at compile time (e.g. COUNT, SUBSTRING, DATE). See supported for which functions are available.

Syntax

impl_supports_fn!(DriverType, SupportsTrait, arg_count0, arg_count1, ...);

• SupportsTrait comes from crate::markers::functions (for example SupportsCount).
• Provide one or more argument counts.
• Use -1 for functions that appear without parentheses (like CURRENT_TIMESTAMP).
• Use impl_supports_fn_any for variadic functions.
• For custom SQL functions (not built-ins), use custom_sql_function!.

Example

impl_supports_fn!(DocDriver, SupportsCount, 0, 1);
impl_supports_fn!(DocDriver, SupportsCurrentTimestamp, -1);