Struct EffectSet 

pub struct EffectSet(/* private fields */);

the set of effects a function performs.

an empty set IS pure – Pure is implicit, not a stored flag. the u8 repr makes union a single | op, is_subset_of a single mask, and equality a one-byte compare. instances are immutable; every operation returns a fresh EffectSet rather than mutating in place. Copy matters because the type checker stores an EffectSet on every typed function and reads it at every call site; one byte is cheaper to copy than to reference.

Default derives EffectSet(0), which equals EffectSet::pure – the type checker initialises every unannotated function at the bottom of the lattice and unions upward during fixed-point ascent.

Implementations

impl EffectSet

pub fn pure() -> Self

the empty set: no flags set, the lattice bottom.

equivalent to is pure annotated functions. constructing a function’s initial EffectSet for fixed-point ascent starts here.

pub fn full() -> Self

every flag set: the lattice top.

used as the upper bound for the unannotated-caller fallback: when the type checker calls a function it cannot resolve a signature for, it treats the call as producing full() so an annotated caller’s check fails closed rather than silently accepting.

pub fn io() -> Self

the singleton set {Io}.

pub fn alloc() -> Self

the singleton set {Alloc}.

pub fn panic() -> Self

the singleton set {Panic}.

pub fn has_io(self) -> bool

is the Io flag set?

pub fn has_alloc(self) -> bool

is the Alloc flag set?

pub fn has_panic(self) -> bool

is the Panic flag set?

pub fn is_pure(self) -> bool

is this the empty set?

true iff no flags are set. an is pure-annotated function’s effect set is exactly this case.

pub fn union(self, other: Self) -> Self

the lattice join: the union of self’s flags and other’s flags.

idempotent (a.union(a) == a), commutative (a.union(b) == b.union(a)), and associative. these properties are what guarantee Plan 4’s fixed-point loop converges monotonically.

pub fn is_subset_of(self, other: Self) -> bool

is every flag set in self also set in other?

reflexive (a.is_subset_of(a) == true), antisymmetric (a ⊆ b and b ⊆ a implies a == b), and transitive. the type checker’s annotation check is inferred.is_subset_of(annotated) – the inferred effect of the body must not exceed what the annotation allows.

pub fn display(&self) -> String

the canonical comma-joined rendering for diagnostics.

flags appear in fixed (Io, Alloc, Panic) order regardless of how the set was constructed, so io().union(alloc()) and alloc().union(io()) both render "io, alloc". an empty set renders "pure". this is the determinism contract the renderer’s byte-identical-output tests depend on.

Trait Implementations

impl Clone for EffectSet

fn clone(&self) -> EffectSet

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for EffectSet

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

Formats the value using the given formatter.

impl Default for EffectSet

fn default() -> EffectSet

Returns the “default value” for a type.

impl Display for EffectSet

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

delegate to EffectSet::display so format!("{e}") produces the canonical comma-joined form. lets EffectViolation messages interpolate effect sets without an explicit .display() call at every site.

impl Hash for EffectSet

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for EffectSet

fn eq(&self, other: &EffectSet) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for EffectSet

impl Eq for EffectSet

impl StructuralPartialEq for EffectSet