fix(lint): noMisleadingReturnType false negative on object keyword

[minseong0324]

I used Claude Code to assist with this implementation.

Summary

Addresses items from #9810: noMisleadingReturnType no longer misses widening from concrete object types, class instances, object literals, tuples, functions, and regular expressions to : object.

Test Plan

Snapshot tests.

[changeset-bot]

🦋 Changeset detected

Latest commit: a715081

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 13 packages

Name	Type
@biomejs/biome	Patch
@biomejs/cli-win32-x64	Patch
@biomejs/cli-win32-arm64	Patch
@biomejs/cli-darwin-x64	Patch
@biomejs/cli-darwin-arm64	Patch
@biomejs/cli-linux-x64	Patch
@biomejs/cli-linux-arm64	Patch
@biomejs/cli-linux-x64-musl	Patch
@biomejs/cli-linux-arm64-musl	Patch
@biomejs/wasm-web	Patch
@biomejs/wasm-bundler	Patch
@biomejs/wasm-nodejs	Patch
@biomejs/backend-jsonrpc	Patch

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[codspeed-hq]

Merging this PR will not alter performance

✅ 58 untouched benchmarks
⏩ 196 skipped benchmarks¹

---

_{Comparing minseong0324:fix/no-misleading-return-type-object-keyword (a715081) with main (d428d76)}

Footnotes

1. 196 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

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Walkthrough

This PR enhances the nursery lint noMisleadingReturnType to detect misleading : object annotations. It introduces a per-body ReturnInfo accumulator, extends AST cast handling via a new AnyTsCastExpression, adds bounded traversal and same-file resolution for cast targets and nominal declarations, refactors nested-function pruning, and adjusts widening/comparison logic so object is treated as wider than concrete object-like shapes. A large set of valid and invalid TypeScript tests for object and Promise<object> returns were added.

Possibly related PRs

• fix(lint): fix false positive in noMisleadingReturnType for nested object widening #10006: Modifies the same noMisleadingReturnType lint implementation and related tests—overlapping return-type narrowing fixes.
• feat(lint): add nursery rule noMisleadingReturnType #9799: Directly touches the noMisleadingReturnType rule, tests and syntax helpers used by this change.
• feat(lint): detect tuple widening and inferred unions in noMisleadingReturnType #9843: Updates type-comparison and widening logic that overlaps with this PR’s object/width semantics.

Suggested labels

A-Type-Inference

Suggested reviewers

• dyc3
• ematipico

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title directly describes the main fix: addressing false negatives in the noMisleadingReturnType rule when detecting object keyword widening.
Description check	✅ Passed	The description clearly relates to the changeset, explaining the fix addresses issue #9810 and that the rule now catches widening to : object annotation.
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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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@crates/biome_js_analyze/src/lint/nursery/no_misleading_return_type.rs`:
- Around line 776-805: Update cast_target_trustworthy so the TsReferenceType arm
treats only NameResolution::ResolvesToObject as trustworthy (remove
NameResolution::NotFound from the trustworthy branch) by changing the match on
resolve_reference_name(&name, anchor) to accept only ResolvesToObject; keep
Narrower -> false. Strengthen intersection_has_object_keyword to ensure an
intersection is considered object-equivalent only when every non-parenthesized
member is provably the object keyword (e.g., require that none of the
intersection members are narrowing shapes like object & { a: number } or
Array<number>) — i.e., iterate intersection.types(), skip errors, and return
true only if every member.omit_parentheses() is AnyTsType::TsNonPrimitiveType(_)
or otherwise proven object-equivalent, otherwise return false. Update/add test
fixtures for unresolved qualified references (e.g., NS.Narrow), intersections
with narrowing members (e.g., object & { a: number }), and generic narrowings
(e.g., Array<number>) to cover these cases.
- Around line 713-715: The current union AnyTsCastExpression includes
TsSatisfiesExpression and causes `satisfies` to be treated like `as` for
object-widening checks; change the logic so TsSatisfiesExpression is not
included in the set of cast/assertion nodes that opt into object-widening
suppression (keep unwrapping TsSatisfiesExpression when performing type
inference but do NOT treat it as an object-keyword assertion for the widening
opt-in path used by the functions/methods that check for object-return
suppression); update the places referenced around the AnyTsCastExpression
declaration and the related handling in the code paths mentioned (also apply the
same exclusion in the analogous code at the 737–749 region) and add a failing
fixture test that covers `function f(): object { return { a: 1 } satisfies
object; }`.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 1e2a0e0d-75a7-4368-8da2-5c4878ef0019

📥 Commits

Reviewing files that changed from the base of the PR and between f785e8c and f35aae2.

⛔ Files ignored due to path filters (2)

• crates/biome_js_analyze/tests/specs/nursery/noMisleadingReturnType/invalid.ts.snap is excluded by !**/*.snap and included by **
• crates/biome_js_analyze/tests/specs/nursery/noMisleadingReturnType/valid.ts.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (4)

• .changeset/clever-otters-swim.md
• crates/biome_js_analyze/src/lint/nursery/no_misleading_return_type.rs
• crates/biome_js_analyze/tests/specs/nursery/noMisleadingReturnType/invalid.ts
• crates/biome_js_analyze/tests/specs/nursery/noMisleadingReturnType/valid.ts

[coderabbitai]

♻️ Duplicate comments (2)

crates/biome_js_analyze/src/lint/nursery/no_misleading_return_type.rs (2)

713-749: ⚠️ Potential issue | 🟠 Major

Do not count satisfies object as an object assertion.

satisfies preserves the expression’s inferred type, so function f(): object { return { a: 1 } satisfies object; } should still report. Unwrap TsSatisfiesExpression for inference, but do not let its target increment object_keyword_casts.

Suggested adjustment

 fn has_object_keyword_assertion(expression: &AnyJsExpression) -> bool {
     let mut stack = vec![expression.clone()];
     while let Some(current_expression) = stack.pop() {
+        if let AnyJsExpression::TsSatisfiesExpression(satisfies_expression) = &current_expression {
+            let Ok(inner_expression) = satisfies_expression.expression() else {
+                return false;
+            };
+            stack.push(inner_expression);
+            continue;
+        }
         if let Some(cast) = AnyTsCastExpression::cast(current_expression.syntax().clone()) {
             let Some(cast_type) = cast.cast_type() else {
                 return false;
             };

TypeScript satisfies operator preserves the inferred expression type and does not widen like a type assertion

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@crates/biome_js_analyze/src/lint/nursery/no_misleading_return_type.rs` around
lines 713 - 749, The current logic treats all AnyTsCastExpression kinds the same
and counts a `satisfies` target as an object assertion; change
has_object_keyword_assertion so that when you encounter
AnyTsCastExpression::TsSatisfiesExpression you unwrap it by pushing its
inner_expression (use AnyTsCastExpression::inner_expression) back onto the
traversal stack for inference but do NOT treat its cast_type as contributing to
object_keyword_casts or as an object keyword assertion; for non-satisfies casts
(TsAsExpression, TsTypeAssertionExpression) keep the existing cast_type checks
and call cast_target_trustworthy as before.

---

776-805: ⚠️ Potential issue | 🟠 Major

Only trust cast targets proven to be object-equivalent.

NotFound and “any intersection containing object” still hide narrower assertions such as as NS.Narrow, as Array<number>, or as (object & { a: number }).

Suggested tightening

         AnyTsType::TsReferenceType(reference_type) => {
             let Some(name) = reference_type_name(&reference_type) else {
-                return true;
+                return false;
             };
-            // `NotFound` deliberately treats unknown names as trustworthy —
-            // TypeScript itself rejects incompatible casts, so an unresolved
-            // name is not a source of misleading widening.
             match resolve_reference_name(&name, anchor) {
-                NameResolution::ResolvesToObject | NameResolution::NotFound => true,
+                NameResolution::ResolvesToObject => true,
+                NameResolution::NotFound => false,
                 NameResolution::Narrower => false,
             }
         }
@@
 fn intersection_has_object_keyword(intersection: &TsIntersectionType) -> bool {
     intersection
         .types()
         .into_iter()
-        .filter_map(|member_result| member_result.ok())
-        .any(|member_ty| matches!(member_ty.omit_parentheses(), AnyTsType::TsNonPrimitiveType(_)))
+        .all(|member_result| {
+            member_result.ok().is_some_and(|member_ty| {
+                matches!(member_ty.omit_parentheses(), AnyTsType::TsNonPrimitiveType(_))
+            })
+        })
 }

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@crates/biome_js_analyze/src/lint/nursery/no_misleading_return_type.rs` around
lines 776 - 805, Change the trust rules so only cast targets provably equivalent
to `object` are trusted: in cast_target_trustworthy, do not treat
NameResolution::NotFound as trustworthy (make it return false instead of true)
and update intersection_has_object_keyword to require that every intersection
member is the `object`-equivalent (i.e., change the .any(...) check to .all(...)
and ensure you call member_ty.omit_parentheses() and match
AnyTsType::TsNonPrimitiveType(_) for each member). These changes affect the
functions cast_target_trustworthy and intersection_has_object_keyword referenced
in the diff.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Duplicate comments:
In `@crates/biome_js_analyze/src/lint/nursery/no_misleading_return_type.rs`:
- Around line 713-749: The current logic treats all AnyTsCastExpression kinds
the same and counts a `satisfies` target as an object assertion; change
has_object_keyword_assertion so that when you encounter
AnyTsCastExpression::TsSatisfiesExpression you unwrap it by pushing its
inner_expression (use AnyTsCastExpression::inner_expression) back onto the
traversal stack for inference but do NOT treat its cast_type as contributing to
object_keyword_casts or as an object keyword assertion; for non-satisfies casts
(TsAsExpression, TsTypeAssertionExpression) keep the existing cast_type checks
and call cast_target_trustworthy as before.
- Around line 776-805: Change the trust rules so only cast targets provably
equivalent to `object` are trusted: in cast_target_trustworthy, do not treat
NameResolution::NotFound as trustworthy (make it return false instead of true)
and update intersection_has_object_keyword to require that every intersection
member is the `object`-equivalent (i.e., change the .any(...) check to .all(...)
and ensure you call member_ty.omit_parentheses() and match
AnyTsType::TsNonPrimitiveType(_) for each member). These changes affect the
functions cast_target_trustworthy and intersection_has_object_keyword referenced
in the diff.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 89140051-4cd1-489f-b5f2-98b777c83c78

📥 Commits

Reviewing files that changed from the base of the PR and between f35aae2 and 9ee5421.

⛔ Files ignored due to path filters (2)

• crates/biome_js_analyze/tests/specs/nursery/noMisleadingReturnType/invalid.ts.snap is excluded by !**/*.snap and included by **
• crates/biome_js_analyze/tests/specs/nursery/noMisleadingReturnType/valid.ts.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (4)

• .changeset/clever-otters-swim.md
• crates/biome_js_analyze/src/lint/nursery/no_misleading_return_type.rs
• crates/biome_js_analyze/tests/specs/nursery/noMisleadingReturnType/invalid.ts
• crates/biome_js_analyze/tests/specs/nursery/noMisleadingReturnType/valid.ts

✅ Files skipped from review due to trivial changes (2)

• .changeset/clever-otters-swim.md
• crates/biome_js_analyze/tests/specs/nursery/noMisleadingReturnType/valid.ts