mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-24 22:02:23 +01:00
Jon Ross-Perkins
f8c8861e5f
This doesn't significantly change logic, although I'm trying to add the location to used state. The issue I'm trying to address is how to identify a declaration as "allowed to be redeclared". Consider: ``` library "a" api; extern fn F(); ``` ``` library "b" api; extern fn F(); ``` ``` library "c" api; import library "a"; import library "b"; var x: auto = F(); fn F(); ``` What currently happens is: 1. On import of "a", `F` becomes ImportRefUnused 2. On import of "b", `F` becomes ImportRefUsed in order to merge. 3. In "c", the call `F()` doesn't change the state. 4. In "c", the declaration `fn F();` needs some breadcrumb to understand whether "F" has been referenced, as in step (3) here. What I want to happen is: 1. On import of "a", `F` becomes ImportRefUnloaded 2. On import of "b", `F` becomes ImportRefLoaded in order to merge. 3. In "c", the call `F()` causes `F` to become ImportRefUsed 4. In "c", the declaration `fn F();` detects that `F` is already ImportRefUsed, and can use the associated `used_id` for a diagnostic about why redeclaring is invalid. Note this PR isn't implementing (4). I'm focused on the refactoring to add a new ImportRef state here.