Scopecomplete

Scopecomplete is a term used in programming language theory to describe a property of a program or language in which every identifier reference encountered during execution can be resolved to a binding within the accessible scope at that point. In practice, scopecomplete means that after applying the language's scope rules—such as lexical or static scoping, plus modules or namespaces—the set of declarations available in the environment provides a unique, well-defined binding for each reference.

Formal notion: A program is scopecomplete if for every reference r to an identifier id at position p, there exists a binding B such that B.binds(id) = decl and the path from p to B is allowed by the scope chain, including enclosing functions and closures. In languages with closures, references may bind to variables in outer scopes via captured environments; scopecomplete ensures these bindings are maintained deterministically under program transformations.

Significance: Scopecomplete is used in discussions of compiler correctness and optimizations that assume stable binding, such as inlining and constant propagation. It helps clarify when scope resolution remains valid under transformations like function extraction or inlining. Not all languages guarantee scopecomplete in every transformation; some require scope normalization or alpha-renaming to preserve it.

Examples: In a nested function scenario, a reference inside an inner function to a variable declared in an outer function is resolved via the closure, contributing to scopecomplete. If a reference refers to a name not declared within any accessible scope, the program is not scopecomplete and would be rejected by a conservative analyzer.

See also: lexical scoping, static scoping, closures, symbol table, name binding, program analysis.