meta.language.classes.single_inheritance

A class or context declaration has at most one extends base.

Read in specification context · design/meta/language.md

Tests and review

Indexed tests and the implementation-completeness and test-adequacy review; no test run is implied.

Implemented sage_meta::declarations_accept_one_base_and_reject_multiple_bases

crates/sage-meta/tests/envelopes.rs · test:envelopes

#![allow(unused)]
fn main() {
#[test]
#[sage::test(meta.language.classes.single_inheritance)]
fn declarations_accept_one_base_and_reject_multiple_bases() {
    for kind in ["class", "context"] {
        let document = valid(&format!(
            r#"{kind} Base {{ """Base.""" }}
            {kind} Child extends crate::Base {{ """Child.""" }}"#
        ));
        assert_eq!(
            class(&document, "Child").base.as_ref().unwrap().segments,
            ["Base"]
        );
        for bases in [
            "crate::Base, crate::Other",
            "crate::Base extends crate::Other",
        ] {
            assert!(
                sage_meta::parse(
                    "demo/crate.sage",
                    &format!(r#"crate demo {{ """Demo.""" }} {kind} Child extends {bases} {{ """Child.""" }}"#),
                )
                .is_err(),
                "accepted multiple bases: {kind} {bases}",
            );
        }
    }
}
}

See more source ↗

Review: Accepted · Codex /root/anchor_191 independent review.

The complete claim limits each class or context declaration to at most one extends base. I independently verified exact byte equality of current parser.rs and envelopes.rs with the historical implementation_sources and test_sources, then reassessed the current claim, sole ordinary implementation association, and complete sole ordinary annotated test. Parser::document shares one optional extends/path branch across class, abstract class, and context, immediately requires an opening brace, and stores that optional base; path parsing consumes only qualified path segments. Thus zero or one base is accepted and comma-separated or repeated-extends bases fail rather than becoming additional bases. The annotated declarations_accept_one_base_and_reject_multiple_bases test loops over class and context, parses Base declarations without extends and Child declarations with one base, asserts the Child base segments equal Base, and asserts parse errors for both multiple-base spellings. Captured envelopes.rs lines 1–65 establish that parse unwraps the real parser result, valid additionally requires empty validation errors, and class selects the named declaration. These meaningful assertions plus the shared parser branch cover the cardinality claim, including the abstract-class branch by source inspection. There are no TODO/N/A entries or deferred prerequisites. Historical rationale remains adequate against current evidence; no edits are needed. This is source inspection and exact baseline comparison, not a new behavioral execution. I ran review start and review read and am recording this report; I did not run tests or a workspace build. The coordinator separately reports 321 passing sage-meta functional tests and a successful root cargo build.

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meta.language.classes.single_inheritance

Implementation

Tests and review