Enum Shape 

pub enum Shape {
    Function,
    Method,
    Closure,
    Record,
    Impl,
    Block,
    Loop,
    Branch,
    Match,
    MatchArm,
    Call,
    Assign,
    VarDecl,
    Return,
    Break,
    Continue,
    Try,
    ExprStmt,
    MacroDef,
    MacroCall,
    Error,
    Native(Lexeme),
}

The cross-language shape vocabulary.

Every variant except Shape::Native means the same thing in all three languages, so structural comparison across files (and, in later phases, across languages) can work on shapes alone. A frontend maps its grammar onto these; whatever does not fit is carried as Shape::Native with the grammar’s own kind name preserved.

Variants

Function

A free function definition.

Method

A method definition (function inside an impl/class/struct body).

Closure

A closure or lambda.

Record

A record definition: struct, class, union or enum.

Impl

An implementation or member-definition container (impl, class body).

Block

A braced statement block.

Loop

A loop of any flavour (for, while, loop, do-while).

Branch

A two-way conditional (if/else chain member).

Match

A multi-way conditional (match, switch).

MatchArm

One arm of a multi-way conditional.

Call

A function, method or macro-like call expression.

Assign

An assignment or compound assignment.

VarDecl

A local variable declaration (let, C/C++ declaration statement).

Return

A return (or expression-position tail return).

Break

An early loop exit (break).

Continue

A loop continuation (continue).

Try

Error propagation or handling (? operator, try/catch).

ExprStmt

An expression used as a statement, not covered by a finer shape.

MacroDef

A macro or preprocessor definition site.

MacroCall

A macro invocation site (not expanded).

Error

A region the parser could not interpret. Children may still be intact.

Native(Lexeme)

A node kept under its native grammar kind because no common shape applies. The kind name takes part in structural comparison, so two native nodes match only when their grammars call them the same thing.

Implementations

impl Shape

pub const fn tag(&self) -> u8

A stable one-byte tag for this shape, for use as fingerprint input.

For Shape::Native the tag alone is not sufficient input: the native kind name must be hashed alongside it, or all native nodes would collapse into one shape.

pub const fn introduces_scope(&self) -> bool

Whether this shape opens a lexical scope for alpha renaming.

This is the structural basis normalization uses to rename identifiers consistently within — and only within — one scope. The judgement is syntactic and shared by all three languages: bodies bind, containers and single statements do not.

pub const fn is_statement(&self) -> bool

Whether nodes of this shape are statements for the purposes of statement sequences and statement-window fragments.

Trait Implementations

impl Clone for Shape

fn clone(&self) -> Shape

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Shape

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

Formats the value using the given formatter.

impl Eq for Shape

impl PartialEq for Shape

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Shape