refactor: deduplicate type narrowing and unification bookkeeping

[R-unic]

Summary

Pure readability refactor, no intended behavior change:

• TypeNarrower repeated the same true/false-branch swap pattern in ApplyBinaryNarrowing/NarrowBaseByProperty/NarrowBaseByElement, and had two near-identical union-unwrapping helpers (GetMemberPropertyType/GetMemberElementType) — unified into shared helpers.
• MacroExpander independently reimplemented the same union-member-property-lookup-and-simplify logic found in TypeNarrower — consolidated into a shared utility (moved onto TypeSimplifier).
• TypeSolver.CheckCircular's UnionType/IntersectionType cases were structurally identical aside from which constructor wraps the result — extracted a shared helper.
• TypeSolver's UnifyObjectTypes/UnifyInstantiatedPair/UnifyFunctionTypes each hand-rolled the same success/updated bookkeeping — consolidated.

Test plan

• dotnet build — succeeds, no warnings
• dotnet test — 1778/1778 pass (this is a behavior-preserving refactor, so an unchanged pass count/results is the main signal)
• Compiled the same input through Loom.CLI before/after — output byte-identical

🤖 Generated with Claude Code

[github-actions]

Qodana for .NET

255 new problems were found

Inspection name	Severity	Problems
Auto-property accessor is never used (private accessibility)	🔶 Warning	6
Redundant using directive	🔶 Warning	5
Auto-property accessor is never used (non-private accessibility)	🔶 Warning	5
Non-accessed positional property (non-private accessibility)	🔶 Warning	4
Redundant argument with default value	🔶 Warning	2
'??' condition is never null according to nullable reference types' annotations	🔶 Warning	1
Redundant name qualifier	🔶 Warning	1
Redundant nullable warning suppression expression	🔶 Warning	1
Type member is never used (private accessibility)	🔶 Warning	1
Unused parameter (private accessibility)	🔶 Warning	1
Unused local variable	🔶 Warning	1
Type member is never used (non-private accessibility)	◽️ Notice	93
Use preferred style of 'new' expression when created type is not evident	◽️ Notice	83
Member can be made private (non-private accessibility)	◽️ Notice	18
Class is never instantiated (non-private accessibility)	◽️ Notice	4
Some values of the enum are not processed inside 'switch' statement	◽️ Notice	4
Auto-property can be made get-only (non-private accessibility)	◽️ Notice	3
Invert 'if' statement to reduce nesting	◽️ Notice	3
RoslynAnalyzers The member referenced by the MemberData attribute returns untyped data rows	◽️ Notice	3
Use preferred style for trailing comma before new line in multiline lists	◽️ Notice	2
RoslynAnalyzers Do not use Enumerable methods on indexable collections	◽️ Notice	2
Remove redundant parentheses	◽️ Notice	1
Auto-property can be made get-only (private accessibility)	◽️ Notice	1
RoslynAnalyzers Use concrete types when possible for improved performance	◽️ Notice	1
Foreach loop can be converted into LINQ-expression but another 'GetEnumerator' method will be used	◽️ Notice	1
Merge null/pattern checks into complex pattern	◽️ Notice	1
Redundant string interpolation	◽️ Notice	1
Replace with 'field' keyword	◽️ Notice	1
Some values of the enum are not processed inside 'switch' statement and are handled via default section	◽️ Notice	1
Tail recursive call can be replaced with loop	◽️ Notice	1
Type member is never accessed via base type (non-private accessibility)	◽️ Notice	1
Method return value is never used (non-private accessibility)	◽️ Notice	1
Literal length can be reduced by using verbatim string	◽️ Notice	1

☁️ View the detailed Qodana report

Detected 1 dependency

Third-party software list

This page lists the third-party software dependencies used in Loom

Dependency	Version	Licenses
Tomlyn	2.6.0	BSD-2-Clause

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