This supersedes #23416

This is a tracking issue for the RFC "3307" (rust-lang/rfcs#3307).

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.

Steps

• Implement the RFC:
  • Remove type ascription from the parser and diagnostics
  • @rust-lang/compiler: Do y'all have a preference as to how far the removal should go? Unparseable AST nodes could be left in the code, for example (perhaps only instantiable by internal macro)
• Adjust documentation: Remove it from the unstable book
• (No stabilization PR necessary)
• Remove the feature gate.

Unresolved Questions

• Should this be completely removed by the compiler, or left behind in a way that cannot be directly accessed through Rust syntax (or requires using a wrapper macro)?
• [ ]

Implementation history