Fixes related to captured types and inference by msridhar · Pull Request #1655 · uber/NullAway

msridhar · 2026-07-25T16:45:12Z

Some initial fixes related to handling of captured types; see #1656 for more issues to handle later.

Here's the relevant example for this one:

final class Test {
    static void reproduce() {
        var future = future();
        run(() -> future.join());
    }
    private static CompletableFuture<?> future() {
        return new CompletableFuture<>();
    }
    private static <T extends @Nullable Object> T run(Action<T> action) {
        return action.run();
    }
    private interface Action<T extends @Nullable Object> {
        T run();
    }
}

The future local variable gets a type CompletableFuture<CAP#1>, where CAP#1 is a captured type variable whose upper bound is @Nullable. Hence, the lambda () -> future.join() may return @Nullable, which is ok given the upper bound of T for run. Before we would report a spurious warning for this case. We also add a test that when T's upper bound is @NonNull we still get an error.

The fix here is to handle captured types exactly like type variables when generating inference constraints and restoring nullness annotations.

Summary by CodeRabbit

Bug Fixes
- Improved nullability constraint propagation for captured generic types.
- Ensured direct nullability annotations are restored correctly when captured types are involved.
- Fixed related generic inference behavior in lambda scenarios with nullable upper/lower bounds.
Tests
- Added new generic lambda tests covering CompletableFuture.join(), including verification of expected diagnostics for conflicting nullability constraints.

msridhar · 2026-07-25T16:45:13Z

This change is part of the following stack:

Fixes related to captured types and inference #1655 ◀
- Remove duplicate NestedAnnotationInfo source from NullAway module #1659

_{Change managed by git-spice.}

codecov · 2026-07-25T16:58:20Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.06%. Comparing base (5ba2284) to head (b01c318).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #1655   +/-   ##
=========================================
  Coverage     88.06%   88.06%           
  Complexity     3076     3076           
=========================================
  Files           105      105           
  Lines         10354    10356    +2     
  Branches       2095     2095           
=========================================
+ Hits           9118     9120    +2     
  Misses          581      581           
  Partials        655      655

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coderabbitai · 2026-07-25T18:29:44Z

Walkthrough

Adds explicit CapturedType handling to subtype constraint propagation and nullness annotation restoration. Adds generic lambda tests covering inference from CompletableFuture.join(), including nullable and conflicting non-null upper bounds.

Possibly related issues

Further address issues involving captured types #1656 — Directly concerns additional CapturedType handling related to this change.

Possibly related PRs

uber/NullAway#1454 — Updates nullness restoration for another wildcard-related type shape.
uber/NullAway#1549 — Extends generic constraint handling for wildcard-captured types.
uber/NullAway#1575 — Addresses lambda inference involving wildcards and captured types.

Suggested labels: jspecify

Suggested reviewers: yuxincs

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title matches the main theme of the changes: captured-type handling and inference-related fixes.
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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Create PR with unit tests
Commit unit tests in branch var-generic-method-inference-bug

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coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java`:
- Around line 188-192: Update both generated Java source strings in
GenericLambdaTests, including the snippets near makeHelper(), to declare package
com.uber before their imports. Keep the existing imports and test logic
unchanged so AnnotatedPackages=com.uber applies to both cases.

🪄 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: ASSERTIVE

Plan: Pro Plus

Run ID: 1bafe23e-8204-4cd6-b309-bf347a785089

📥 Commits

Reviewing files that changed from the base of the PR and between 6d57adf and fe86b32.

📒 Files selected for processing (3)

nullaway/src/main/java/com/uber/nullaway/generics/ConstraintSolverImpl.java
nullaway/src/main/java/com/uber/nullaway/generics/TypeSubstitutionUtils.java
nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java

coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java`:
- Around line 183-210: Add Javadoc describing the nullable-upper-bound inference
scenario for varAndGenericInference in
nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java lines
183-210. Also add Javadoc describing the conflicting non-null upper-bound
diagnostic scenario for the test method in lines 212-240; no other changes are
needed.

🪄 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: ASSERTIVE

Plan: Pro Plus

Run ID: 881d0b62-6755-4159-b4d0-fd732082badb

📥 Commits

Reviewing files that changed from the base of the PR and between fe86b32 and b01c318.

📒 Files selected for processing (3)

nullaway/src/main/java/com/uber/nullaway/generics/ConstraintSolverImpl.java
nullaway/src/main/java/com/uber/nullaway/generics/TypeSubstitutionUtils.java
nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java

coderabbitai · 2026-07-26T21:43:01Z

+  @Test
+  public void varAndGenericInference() {
+    makeHelper()
+        .addSourceLines(
+            "Test.java",
+            """
+            import java.util.concurrent.CompletableFuture;
+            import org.jspecify.annotations.NullMarked;
+            import org.jspecify.annotations.Nullable;
+            @NullMarked
+            final class Test {
+                static void reproduce() {
+                    var future = future();
+                    run(() -> future.join());
+                }
+                private static CompletableFuture<?> future() {
+                    return new CompletableFuture<>();
+                }
+                private static <T extends @Nullable Object> T run(Action<T> action) {
+                    return action.run();
+                }
+                private interface Action<T extends @Nullable Object> {
+                    T run();
+                }
+            }
+            """)
+        .doTest();
+  }


📐 Maintainability & Code Quality | 🟠 Major | ⚡ Quick win

Add Javadoc for the new non-trivial test methods.

nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java#L183-L210: Document the nullable-upper-bound inference scenario.

nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java#L212-L240: Document the conflicting non-null upper-bound diagnostic scenario.

As per coding guidelines, “Add Javadoc to every non-trivial method, including private methods.”

📍 Affects 1 file

nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java#L183-L210 (this comment)

nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java#L212-L240

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the rest with a brief reason, keep changes minimal, and validate. In `@nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java` around lines 183 - 210, Add Javadoc describing the nullable-upper-bound inference scenario for varAndGenericInference in nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java lines 183-210. Also add Javadoc describing the conflicting non-null upper-bound diagnostic scenario for the test method in lines 212-240; no other changes are needed.

Source: Coding guidelines

msridhar mentioned this pull request Jul 25, 2026

Further address issues involving captured types #1656

Open

msridhar mentioned this pull request Jul 25, 2026

Fix inference bug with generic instance methods #1654

Merged

msridhar marked this pull request as ready for review July 25, 2026 18:28

msridhar requested a review from lazaroclapp July 25, 2026 18:29

msridhar force-pushed the var-generic-method-inference-bug branch from 899eacc to 6d57adf Compare July 25, 2026 18:29

msridhar mentioned this pull request Jul 25, 2026

Enable inference failure warnings in experimental mode, and fix related bug in library models #1649

Merged

lazaroclapp approved these changes Jul 25, 2026

View reviewed changes

msridhar force-pushed the var-generic-method-inference-bug branch from a525370 to 6d57adf Compare July 25, 2026 23:53

msridhar mentioned this pull request Jul 26, 2026

Update to latest Shadow plugin #1658

Merged

msridhar force-pushed the inference-wildcard-bug branch from 34ffd0a to 4da9aa3 Compare July 26, 2026 00:10

msridhar force-pushed the var-generic-method-inference-bug branch from 6d57adf to fe86b32 Compare July 26, 2026 00:10

coderabbitai Bot reviewed Jul 26, 2026

View reviewed changes

Comment thread nullaway/src/test/java/com/uber/nullaway/jspecify/GenericLambdaTests.java

msridhar mentioned this pull request Jul 26, 2026

Remove duplicate NestedAnnotationInfo source from NullAway module #1659

Merged

msridhar force-pushed the inference-wildcard-bug branch from 4da9aa3 to 39d5b75 Compare July 26, 2026 20:59

Base automatically changed from inference-wildcard-bug to master July 26, 2026 21:13

Fixes related to captured types and inference

b01c318

msridhar force-pushed the var-generic-method-inference-bug branch from fe86b32 to b01c318 Compare July 26, 2026 21:40

msridhar enabled auto-merge (squash) July 26, 2026 21:40

coderabbitai Bot reviewed Jul 26, 2026

View reviewed changes

msridhar merged commit 53f5dc0 into master Jul 26, 2026
14 checks passed

msridhar deleted the var-generic-method-inference-bug branch July 26, 2026 21:56

This was referenced Jul 31, 2026

Handle interaction of captured types and library models #1666

Merged

Follow-on fix for restoring annotation on captured type wildcards #1667

Merged

Harden TypeSubstitutionUtils type copies #1669

Open

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Fixes related to captured types and inference - #1655

Fixes related to captured types and inference#1655
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