Module sema

Semantic analysis.

This module primarily contains the type environment and term environment.

The type environment is constructed by analyzing an input AST. The type environment records the types used in the input source and the types of our various rules and symbols. ISLE’s type system is intentionally easy to check, only requires a single pass over the AST, and doesn’t require any unification or anything like that.

The term environment is constructed from both the AST and type environment. It is sort of a typed and reorganized AST that more directly reflects ISLE semantics than the input ISLE source code (where as the AST is the opposite).

Structs

• BoundVar
  A name bound in a pattern or let-expression.
• ExternalSig
  An external function signature.
• Field
  A field of a Variant.
• FieldId
  The id of a field inside a variant.
• IfLet
  An if-let clause with a subpattern match on an expr after the main LHS matches.
• Rule
  A term rewrite rule.
• RuleId
  The id of an interned rule inside the TermEnv.
• Sym
  The id of an interned symbol.
• Term
  A term.
• TermEnv
  The term environment.
• TermFlags
  Flags from a term’s declaration with (decl ...).
• TermId
  The id of an interned term inside the TermEnv.
• TypeEnv
  The type environment.
• TypeId
  The id of an interned type inside the TypeEnv.
• VarId
  The id of a bound variable inside a Bindings.
• Variant
  A variant of an enum.
• VariantId
  The id of a variant inside an enum.
• VisitedExpr
  Information about an expression after it has been fully visited in RuleVisitor::add_expr.

Enums

• ConstructorKind
  The kind of a constructor for a term.
• Expr
  A right-hand side expression of some rule.
• ExtractorKind
  The kind of an extractor for a term.
• Pattern
  A left-hand side pattern of some rule.
• ReturnKind
  How many values a function can return.
• TermKind
  The kind of a term.
• Type
  A type.

Traits

• ExprVisitor
  Visitor interface for Exprs. Visitors can return an arbitrary identifier for each subexpression, which is threaded through to subsequent calls into the visitor.
• PatternVisitor
  Visitor interface for Patterns. Visitors can assign an arbitrary identifier to each subpattern, which is threaded through to subsequent calls into the visitor.
• RuleVisitor
  Visitor interface for Rules. Visitors must be able to visit patterns by implementing PatternVisitor, and to visit expressions by providing a type that implements ExprVisitor.