fix(hir): dispatch Array-mutator methods on interface-typed receivers to their own method

[machineloop]

Summary

A method whose name collides with an Array.prototype mutator (push/pop/shift/…),
called on a receiver whose static type is a non-class named type (a user interface or a
function/factory return type), was folded to the array fast-path intrinsic instead of the
object's own method — so the call silently no-opped. This extends the #5139 fix (which only
covered any-typed receivers) to interface-typed and factory-return-typed receivers.

Changes

• crates/perry-hir/src/lower/context.rs — add LoweringContext::is_interface_type(name)
  (a name registered in self.interfaces).
• crates/perry-hir/src/lower/expr_call/local_array_methods.rs and …/array_only_methods.rs
  — the is_user_class_* Type::Named arm now also accepts ctx.is_interface_type(name), so
  an interface receiver skips the array-only-method fold and dispatches to its own method.
  (Kept the check precise rather than a blanket Type::Named(_) => true, so TypedArrays —
  Int8Array etc. — still legitimately fold for fill/map; real arrays are never Type::Named.)
• crates/perry/tests/interface_typed_arraylike_method_dispatch.rs — regression tests.

Related issue

Refs #5139 (extends that fix to interface- / factory-return-typed receivers). No dedicated
issue — happy to file one for tracking if preferred.

Test plan

cargo test -p perry --test interface_typed_arraylike_method_dispatch   # 3 passed
cargo fmt -p perry-hir -p perry --check                                # clean
cargo build --release --workspace --exclude perry-ui-{ios,tvos,watchos,gtk4,android,windows}

TDD red→green: before the fix the interface cases printed len=0 (the push was dropped);
after, len=2. The real-array control (number[] push/pop) still prints sum=3 len=2 popped=3.

• cargo build --release -p perry clean (the crates this change touches). The full
  --workspace release build fails only on windows-future — a Windows-only transitive
  dep that can't compile on this macOS host (env limitation, unrelated to this change).
• cargo test --workspace … passes — my new tests pass; the suite's only failures
  (integer_locals_provenance, functional_batch2_regressions, and a
  blocklist_addsubnet_prefix TempDir::join compile break) reproduce identically on
  clean main without this change, so they are pre-existing and unrelated.
• (if user-facing) Added a #[test] in the affected crate (crates/perry/tests/)
• (if CLI / stdlib / runtime API changed) Updated docs/src/ — N/A (internal HIR dispatch)
• (if touching a platform UI backend) — N/A

Screenshots / output

interface Sink { items: string[]; push(x: string): void; }
const s: Sink = { items: [], push(x) { this.items.push(x); } };
s.push("a"); s.push("b");
console.log("len=" + s.items.length);
// before: len=0   after: len=2

Checklist

• I have NOT bumped the workspace version or edited CLAUDE.md / CHANGELOG.md
• My commits follow the loose fix: prefix convention
• I've read CONTRIBUTING.md and agree to the Code of Conduct

Summary by CodeRabbit

• Bug Fixes

  • Fixed incorrect handling of method calls on interface-typed receiver objects. Previously, these were being incorrectly optimized as array operations instead of dispatching to the intended methods.

• Tests

  • Added regression tests for method dispatch on interface-typed receiver objects.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 39595b7f-0b93-4a98-9301-3a9852e94ac1

📥 Commits

Reviewing files that changed from the base of the PR and between d30bfa5 and e6a1905.

📒 Files selected for processing (4)

• crates/perry-hir/src/lower/context.rs
• crates/perry-hir/src/lower/expr_call/array_only_methods.rs
• crates/perry-hir/src/lower/expr_call/local_array_methods.rs
• crates/perry/tests/interface_typed_arraylike_method_dispatch.rs

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📝 Walkthrough

Walkthrough

Adds is_interface_type to LoweringContext and uses it in two array-method lowering guards (try_array_only_methods, try_local_array_methods) so that interface-typed named receivers are treated as user instances and skip the array fast-path. Three regression tests verify interface, factory-returned interface, and real array dispatch behavior.

Changes

Interface receiver guard for array fast-path lowering

Layer / File(s)	Summary
is_interface_type predicate crates/perry-hir/src/lower/context.rs	Adds pub(crate) fn is_interface_type(&self, name: &str) -> bool to LoweringContext, checking self.interfaces to determine whether a name is a declared interface.
Array fast-path guard updates crates/perry-hir/src/lower/expr_call/array_only_methods.rs, crates/perry-hir/src/lower/expr_call/local_array_methods.rs	Extends the Type::Named receiver checks in try_array_only_methods (is_user_class_receiver) and try_local_array_methods (is_user_class_instance) to also bail when ctx.is_interface_type(name) is true, preventing array built-in fast-paths from being applied to interface-typed objects.
Regression tests crates/perry/tests/interface_typed_arraylike_method_dispatch.rs	Adds compile_and_run helper and three end-to-end tests: an interface-typed receiver with its own push, a factory-function-returned interface receiver, and a control test confirming real array push/pop semantics are unchanged.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• PerryTS/perry#5194: Modifies the same array-mutator lowering files to skip the array fast-path based on Any/Unknown/None receiver static types, directly adjacent to the interface-type guard added here.
• PerryTS/perry#5386: Updates the same try_array_only_methods/try_local_array_methods dispatch guards in the same directory to prevent incorrect array folding based on receiver type classification.
• PerryTS/perry#5454: Changes try_array_only_methods folding decisions for push/indexOf/includes based on receiver static form, the same mechanism extended here for interface types.

Poem

🐇 A rabbit once typed with an interface in hand,
And push tried to fold where it shouldn't have land—
is_interface_type said "nope, bail out of here!"
The fast-path stepped back, and dispatch rang clear.
Three tests confirmed arrays still hop as they should,
The bug is now fixed in the lowering wood! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: fixing array-mutator method dispatch on interface-typed receivers, which aligns with the PR's core objective.
Description check	✅ Passed	The PR description comprehensively covers the summary, changes, related issue, test plan with commands, and all checklist items are addressed.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[proggeramlug]

Thanks @machineloop great PR