feat(monomorphize): richer type-alias bodies (intersection, DNF, closure signatures)

[math3usmartins]

Additions that bring type-alias bodies to parity with directly-written slot types:

• Intersection & DNF bodies — A & B, (A & B) | C
• Closure-signature bodies — Closure(int): bool, generic Mapper<T, R>
• Closure signatures as compound members — ?Closure(...), Foo | Closure(...), Foo & Closure(...)

[greptile-apps]

Greptile Summary

The PR expands type-alias bodies to support intersections, DNF expressions, and closure signatures, including generic and compound closure members.

• Introduces a DNF-based AliasBody representation and compound-member deduplication.
• Extends alias parsing, substitution, validation, and AST construction.
• Adds integration fixtures and updates documentation for the richer alias syntax.

Confidence Score: 4/5

The duplicate-member normalization defect should be fixed before merging because valid alias expansion can emit a PHP type that fails to compile.

Alias deduplication preserves case in its identity key, allowing differently cased references to the same PHP class to survive into an intersection or DNF and trigger PHP's duplicate-type error.

Files Needing Attention: src/Transpiler/Monomorphize/AliasBody.php

Important Files Changed

Filename	Overview
src/Transpiler/Monomorphize/AliasBody.php	Adds the DNF representation and deduplication helpers, but duplicate class-like members are compared case-sensitively.
src/Transpiler/Monomorphize/XphpSourceParser.php	Extends alias parsing, recursive expansion, validation, and AST emission for intersections, DNF, and closure signatures.
test/Transpiler/Monomorphize/TypeAliasIntegrationTest.php	Adds broad compile/check and runtime coverage for richer alias bodies, though mixed-case duplicate members are not covered.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
    A[Type alias declaration] --> B[Parse body expression]
    B --> C[Normalize to AliasBody DNF]
    C --> D[Resolve and substitute aliases]
    D --> E[Deduplicate clauses and leaves]
    E --> F[Construct PHP union/intersection/Closure AST]
    F --> G[Compile or check emitted program]

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