Function validate_query_as 

pub fn validate_query_as(
    struct_name: &str,
    sql: &str,
) -> Result<(), ValidationError>

Validate that sql is structurally compatible with struct_name.

Parameters

• struct_name: the Rust struct ident as a string (e.g. "User"). Used for registry lookup via the struct→table index and for diagnostics.
• sql: the raw SQL string literal from query_as!(T, "...").

Errors

Returns a ValidationError if validation fails — e.g. the struct is not registered, SQL has a syntax error, referenced tables are not registered, or the result schema is missing columns the struct requires.