Enum Set 

pub enum Set<T> {
    Unset,
    Null,
    Value(T),
}

One field of a generated Setter: unset, NULL, or a value — three states, distinguished by type.

The three states are the whole point (bob’s omit/null/value): an unset field does not appear in the INSERT or UPDATE at all — the column keeps its database default on insert and its current value on update — while Null writes SQL NULL explicitly. Collapsing the first two into Option would make “leave it alone” and “erase it” the same call site, which is precisely the bug this type exists to prevent.

Default is Unset, which is what makes the struct-update spelling work:

users::table().insert(users::Setter {
    name: set("Stephen"),
    email: null(),
    ..Default::default()      // every other column: untouched
})

Null is representable for every column, NOT NULL ones included — the constraint violation is the database’s to report, exactly as it is for raw SQL. Encoding nullability in the Setter’s types was considered and rejected: it would split Set<T> into two vocabularies and make every generated field’s type depend on a constraint the schema can change, for a check the engine performs anyway.

Variants

Unset

Not mentioned: the field contributes nothing to the statement.

Null

Explicitly NULL, bound as an argument.

Value(T)

A value, bound as an argument.

Implementations

impl<T> Set<T>

pub fn is_unset(&self) -> bool

Whether the field is Unset and so contributes nothing.

impl<T: ToValue> Set<T>

pub fn into_expr(self) -> Option<Expr>

The bound expression this field contributes: None when unset, a bound NULL for Set::Null, a bound argument for a value.

Always a placeholder, never an inline literal — the same binding-only contract every mapped type follows (docs/type-mappings.md).

pub fn push_into( self, column: &'static str, columns: &mut Vec<&'static str>, values: &mut Vec<Expr>, )

Contribute this field to an INSERT’s column and value lists — one call per field is the shape generated insert_query bodies take.

Trait Implementations

impl<T: Clone> Clone for Set<T>

fn clone(&self) -> Set<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Copy> Copy for Set<T>

impl<T: Debug> Debug for Set<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for Set<T>

fn default() -> Set<T>

Returns the “default value” for a type.

impl<T: Eq> Eq for Set<T>

impl<T: PartialEq> PartialEq for Set<T>

fn eq(&self, other: &Set<T>) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl<T: PartialEq> StructuralPartialEq for Set<T>