Builtin SymbolIds are a hard-coded list of 21 names; other std declarations are numbered per program

LIMIT-NAME-RESOLUTION-004

Only 18 builtin types and 3 aspects have fixed ids, kept in Rust beside the std::core module file; every other std declaration gets an id from a per-program sorted pass.

Lifecycle

known

Owner

metel-frontend

Scope

architecture/spec/name-resolution.md#name-resolution

Origin

maintainer review of metel-frontend/src/identity/symbols.rs

Affects · linked records

arch.name-resolution.requirement-1architecture requirement

metel-frontend/src/identity/symbols.rscode path

new metel-frontend/src/identity/symbols.rscode

limitationKnown limitations ↗

Limitation

SymbolTable::new pre-seeds exactly 21 std::core names at fixed ids: 18 types (boolean, String, Char, the sized integers and floats, List, Perhaps, Result, Range, RangeInclusive) and 3 aspects (Display, Iterable, From). The list is Rust constants (SYM_TYPE_*, SYM_ASPECT_*) plus one map.insert per name. The ranges 19-49, 53-99 and 100-999 are reserved "for future stdlib types/aspects/expansion" and are unused. Every other std::core declaration, for example Copy and Drop, is interned by the name resolver like user code. intern_all_symbols sorts every declaration by (module path, name) before interning (metel-core#1129), so an id does not depend on the order modules were loaded; but it is the declaration's rank in that sorted list, so it shifts whenever a program adds or removes a declaration. Code that needs these std items looks them up by (module, name) (coherence.rs does this for Copy and Drop).

Impact

• Builtin identity has two sources of truth: the Rust table here and the std::core module file (ADR-0039). Adding a std type that the runtime must register under a fixed id means editing both.
• The ids of std declarations outside the 21 are stable for a given program whatever the load order, but they are ranks in that program's sorted declaration list, so they cannot be treated as well-known across programs.
• The reserved ranges document an intent that the code does not use.

None of this is observable from a Metel program. It is read from the code, so there is no reproducing fixture.

Affects

• arch.name-resolution.requirement-1
• metel-frontend/src/identity/symbols.rs (SymbolTable::new, the SYM_* constants)

• metel-frontend/src/identity/symbols.rs::new

Resolution

None yet. Generating the fixed ids from the std::core declarations, or dropping the fixed ids in favour of name lookup everywhere, would remove the second source of truth.