ADR-070 made Connection hold Box<dyn BidiStreamSource> so downstream
crates can add connection shapes without editing core. The trait and
three built-in impls landed, but the public constructor that lets a
downstream crate construct a Connection from its own BidiStreamSource
impl was never added — the source field is private with no from_source
constructor. The channels POC update surfaced this when it tried to
use the trait directly and found no way to build a Connection from a
ChannelBidiStreamSource.
This is a gap in the ADR-070 implementation, not a new decision. ADR-070
§Consequences says 'the channels crate implements ChannelBidiStreamSource
in its own crate and constructs Connection from it' — the constructor for
that path is what was missing.
- ADR-070: add from_source to the Constructors table + reword the
downstream-crates paragraph to make the two paths explicit
(from_source for custom impls; from_quinn/from_iroh/from_stream for
built-in impls)
- core-types.md: add from_source to the impl Connection block, the
built-in implementations table, and the design-decisions table entry
- tasks/core/connection-from-source-constructor.md: the implementation
task (one constructor + one test, scope narrow, risk low)
glm-5.2
02c5b9e039