[asukaminato0721]

Summary

Record regression cases before replacing the union display changes in #2466. Related to #1115.

The tests cover an unannotated decorator, an annotated alias combined with another type, repeated union composition, generic substitution that collapses to the alias, and a shared alias imported through two modules.

Test checks named and anonymous unions through twenty nested tuple levels. Each must visit 5 * depth + 1 Type nodes. This detects the exponential display-payload duplication reported in the old review.

This PR contains tests only. The repeated-composition test marks the existing loss of the alias name as a known display bug. Its semantic assert_type checks that no union members disappear.

• I am a human, and I fully understand the code I am submitting.

Test Plan

The following checks passed on Linux:

cargo test -p pyrefly --lib alias_display_
cargo test -p pyrefly --lib test_inferred_decorator_union_alias_display
cargo test -p pyrefly_types test_union_alias_nested_tuple_growth_is_linear
python3 test.py --no-test --no-tensor-shapes --no-conformance --no-jsonschema --no-extension

The nested traversal test checks named and anonymous unions through twenty levels. Both visit 5 * depth + 1 type nodes.

[meta-codesync]

This pull request has been imported. If you are a Meta employee, you can view this in D128365598. (Because this pull request was imported automatically, there will not be any future comments.)

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[stroxler]

Review automatically exported from Phabricator review in Meta.

[meta-codesync]

This pull request has been merged in 12064f9.