[ty] Deduplicate retained scope inference types

[charliermarsh]

Summary

Scope inference retains a type for every expression in the scope. Many expressions share the same type, but the existing frozen map stores a complete Type value in every entry.

This adds a frozen map representation that stores each distinct value once and maps sorted keys to compact value indices. Scope inference uses the new representation when freezing its expression types, and cycle normalization rebuilds the table so normalized values are deduplicated again.

[astral-sh-bot]

Typing conformance results

No changes detected ✅

Current numbers

The percentage of diagnostics emitted that were expected errors held steady at 92.23%. The percentage of expected errors that received a diagnostic held steady at 87.42%. The number of fully passing files held steady at 92/134.

[astral-sh-bot]

Memory usage report

Summary

Project	Old	New	Diff	Outcome
flake8	35.38MB	35.29MB	-0.25% (90.01kB)	⬇️
trio	87.75MB	87.23MB	-0.59% (534.12kB)	⬇️
sphinx	207.56MB	205.71MB	-0.89% (1.85MB)	⬇️
prefect	564.13MB	556.27MB	-1.39% (7.86MB)	⬇️

Significant changes

Click to expand detailed breakdown

flake8

Name	Old	New	Diff	Outcome
infer_scope_types_impl	788.72kB	698.71kB	-11.41% (90.01kB)	⬇️

trio

Name	Old	New	Diff	Outcome
infer_scope_types_impl	3.78MB	3.25MB	-13.81% (534.12kB)	⬇️

sphinx

Name	Old	New	Diff	Outcome
infer_scope_types_impl	12.55MB	10.69MB	-14.76% (1.85MB)	⬇️

prefect

Name	Old	New	Diff	Outcome
infer_scope_types_impl	47.64MB	39.79MB	-16.50% (7.86MB)	⬇️

[astral-sh-bot]

ecosystem-analyzer results

No diagnostic changes detected ✅

Full report with detailed diff (timing results)