Skip `var` when target type inference widens a generic argument - #1103

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timtebeek merged 1 commit into

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tim/fix-javasourcefile-list-type

May 16, 2026

timtebeek commented May 16, 2026

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Summary

List<I> x = singletonList(c) where c is a C extends I keeps the LST type as List<I> via target type inference, but converting to var x = List.of(c) makes javac re-infer List<C> — breaking any downstream usage that requires the declared supertype.

UseVarForGenericMethodInvocations now detects this by checking each argument against its resolved parameter type: when the parameter is a bare (non-parameterized) class that is a strict supertype of the argument, target inference widened a <T> substitution and the conversion is skipped.

Test plan

New test declaredSupertypeWidensTypeArgument in UseVarForGenericMethodInvocationsTest
All existing tests in org.openrewrite.java.migrate.lang.var.* pass


          Skip var when target type inference widens a generic argument

c13a2e6

`List<I> x = singletonList(c)` where `c` is a `C extends I` keeps the
LST type as `List<I>` via target type inference. Converting to
`var x = List.of(c)` drops the target context, so javac re-infers
`List<C>` and downstream usages expecting `List<I>` fail to compile.

Detect the widening by comparing each argument's type to its resolved
parameter type: when the parameter is a bare class (not parameterized)
that is a strict supertype of the argument, target inference widened
a `<T>` substitution, and switching to `var` would narrow it back.

moderne-meeseeks Bot added this to OpenRewrite

moderne-meeseeks Bot assigned timtebeek

github-project-automation Bot moved this to In Progress in OpenRewrite

timtebeek merged commit 568b7a9 into main

1 check passed

timtebeek deleted the tim/fix-javasourcefile-list-type branch

May 16, 2026 11:34

github-project-automation Bot moved this from In Progress to Done in OpenRewrite

mergify Bot added a commit to robfrank/linklift that referenced this pull request


          chore(deps): bump org.openrewrite.recipe:rewrite-migrate-java from 3.…

b60e1b8

…34.0 to 3.36.0 [skip ci]

Bumps [org.openrewrite.recipe:rewrite-migrate-java](https://github.com/openrewrite/rewrite-migrate-java) from 3.34.0 to 3.36.0.
Release notes

*Sourced from [org.openrewrite.recipe:rewrite-migrate-java's releases](https://github.com/openrewrite/rewrite-migrate-java/releases).*

> 3.36.0
> ------
>
> What's Changed
> --------------
>
> * Move StringFormatted recipe from Java 17 upgrade to Java best practices by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1106](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1106)
> * Skip `IfElseIfConstructToSwitch` when a trailing non-`== null` binary check is present by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1109](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1109)
> * Skip `UseTextBlocks` when literal value matches its source by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1111](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1111)
> * Skip `UseMapOf` for `HashMap` subclasses like `LinkedHashMap` and `TreeMap` by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1113](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1113)
> * Skip `RenameUnderscoreIdentifier` on Kotlin and Groovy sources by [`@MBoegers`](https://github.com/MBoegers) in [openrewrite/rewrite-migrate-java#1114](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1114)
> * Do not add `java.io.IO` import in `ReplaceSystemOutWithIOPrint` by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1118](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1118)
> * fix: do not replace lambda params with underscore when used as assignment target by [`@darrencilia`](https://github.com/darrencilia) in [openrewrite/rewrite-migrate-java#1117](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1117)
> * Route WSS4J message.token classes to their real 2.x packages by [`@Jenson3210`](https://github.com/Jenson3210) in [openrewrite/rewrite-migrate-java#1122](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1122)
> * Migrate `com.sun.xml.bind.marshaller.NamespacePrefixMapper` to `org.glassfish.jaxb.runtime.marshaller.NamespacePrefixMapper` by [`@Jenson3210`](https://github.com/Jenson3210) in [openrewrite/rewrite-migrate-java#1121](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1121)
> * Fix `RefineSwitchCases` generating invalid guard on enum constant labels by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1124](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1124)
> * Skip unparseable Java versions in FindJavaVersion instead of reporting -1 by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1125](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1125)
>
> New Contributors
> ----------------
>
> * [`@darrencilia`](https://github.com/darrencilia) made their first contribution in [openrewrite/rewrite-migrate-java#1117](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1117)
>
> **Full Changelog**: <openrewrite/rewrite-migrate-java@v3.35.0...v3.36.0>
>
> 3.35.0
> ------
>
> What's Changed
> --------------
>
> * Add `java.io.IO` import in `ReplaceSystemOutWithIOPrint` by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1093](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1093)
> * Skip `UseMapOf` when `put()` argument is a null literal by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1094](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1094)
> * Migrate JAXB XJC binding files declaring version 2.0/2.1/2.2 by [`@MBoegers`](https://github.com/MBoegers) in [openrewrite/rewrite-migrate-java#1098](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1098)
> * Preserve explicit type arguments in MigrateCollections\* recipes by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1099](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1099)
> * Route Maven through Moderne Artifactory cache to avoid HTTP 429 by [`@Jenson3210`](https://github.com/Jenson3210) in [openrewrite/rewrite-migrate-java#1096](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1096)
> * Load sun.internal.new[Class].jar directly to fix CI test failures by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1101](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1101)
> * Skip explicit type arguments containing wildcards in `UseVarForGenericMethodInvocations` by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1102](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1102)
> * Skip `var` when target type inference widens a generic argument by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1103](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1103)
> * Skip `IfElseIfConstructToSwitch` when `instanceof` types are missing by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1095](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1095)
> * Revert inline Maven mirror (now in gh-automation#95) by [`@Jenson3210`](https://github.com/Jenson3210) in [openrewrite/rewrite-migrate-java#1104](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1104)
> * Aggregate FindJavaVersion to one row per repository by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1105](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1105)
>
> **Full Changelog**: <openrewrite/rewrite-migrate-java@v3.34.1...v3.35.0>
>
> v3.34.1
> -------
>
> What's Changed
> --------------
>
> * OpenRewrite [v8.81.6](https://github.com/openrewrite/rewrite/releases/tag/v8.81.6)
> * Refresh UpdateSdkManTest fixtures after SDKMAN CSV update by [`@steve-aom-elliott`](https://github.com/steve-aom-elliott) in [openrewrite/rewrite-migrate-java#1073](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1073)
> * Add more static analysis recipes to java-best-practices by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1075](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1075)
> * OpenRewrite recipe best practices by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1074](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1074)
> * Add jspecify hyperlink by [`@sullis`](https://github.com/sullis) in [openrewrite/rewrite-migrate-java#1076](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1076)
> * Skip `var` when reassignment relies on declared supertype by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1078](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1078)
> * Keep parentheses when renaming typed lambda parameter to underscore by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1082](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1082)
> * Document null-probing semantic differences in singleton migrations by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1081](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1081)
> * Skip main migration when referenced as static API by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1084](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1084)
> * Skip `Immutable*.copyOf` rewrite when argument is not a `Collection` by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1089](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1089)
> * Keep block body when refined switch arm contains an if statement by [`@timtebeek`](https://github.com/timtebeek) in [openrewrite/rewrite-migrate-java#1088](https://redirect.github.com/openrewrite/rewrite-migrate-java/pull/1088)

... (truncated)


Commits

* [`d4df178`](openrewrite/rewrite-migrate-java@d4df178) Skip unparseable Java versions in FindJavaVersion instead of reporting -1 ([#1](https://redirect.github.com/openrewrite/rewrite-migrate-java/issues/1)...
* [`b8a298e`](openrewrite/rewrite-migrate-java@b8a298e) Fix `RefineSwitchCases` generating invalid guard on enum constant labels ([#1124](https://redirect.github.com/openrewrite/rewrite-migrate-java/issues/1124))
* [`c7f400b`](openrewrite/rewrite-migrate-java@c7f400b) [Auto] SDKMAN! Java candidates as of 2026-06-01T1550
* [`fca7c7c`](openrewrite/rewrite-migrate-java@fca7c7c) Migrate `com.sun.xml.bind.marshaller.NamespacePrefixMapper` to `org.glassfish...
* [`74017b2`](openrewrite/rewrite-migrate-java@74017b2) Route WSS4J message.token classes to their real 2.x packages ([#1122](https://redirect.github.com/openrewrite/rewrite-migrate-java/issues/1122))
* [`52b0808`](openrewrite/rewrite-migrate-java@52b0808) OpenRewrite recipe best practices
* [`23e5804`](openrewrite/rewrite-migrate-java@23e5804) Update Gradle wrapper 9.5.1
* [`21548bd`](openrewrite/rewrite-migrate-java@21548bd) fix: do not replace lambda params with underscore when used as assignment tar...
* [`61e7d90`](openrewrite/rewrite-migrate-java@61e7d90) Do not add `java.io.IO` import in `ReplaceSystemOutWithIOPrint` ([#1118](https://redirect.github.com/openrewrite/rewrite-migrate-java/issues/1118))
* [`dec86d0`](openrewrite/rewrite-migrate-java@dec86d0) Skip `RenameUnderscoreIdentifier` on Kotlin and Groovy sources ([#1114](https://redirect.github.com/openrewrite/rewrite-migrate-java/issues/1114))
* Additional commits viewable in [compare view](openrewrite/rewrite-migrate-java@v3.34.0...v3.36.0)
  
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