Scala 3 Migration Guide

Compiler Options Lookup Table

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This table lists the Scala 2.13 compiler options with their equivalent in Scala 3. Some options have cross-version support, such as -Vprint. Others have a close equivalent with a different name. A number of Scala 2 options have no equivalent in Scala 3, such as options for debugging Scala 2 macros.

The compiler options are shown as displayed by the help output scalac -help, scalac -X, etc. A few aliases are shown here, but most older aliases, such as -Xprint for -Vprint, or -Ytyper-debug for -Vtyper, are listed by the latest name.

The option groups -V and -W were introduced in Scala 2.13, for "verbose" options that request additional diagnostic output and "warnings" that request additional checks which may or may not indicate errors in code. -Werror elevates warnings to errors, and -Wconf allows precise control over warnings by either ignoring them or taking them as errors. The configuration string for -Wconf will likely require adjustment when migrating to Scala 3, since the configuration syntax and the error messages it matches are different.

Status	Meaning
	It is available in Scala 3.
`<new-name>`	It has been renamed to `<new-name>`.
	It is not yet available but could be added later.

The current comparison is based on Scala 2.13.10 and 3.3.0.

Standard Settings

2.13.x	3.3.x
`-Dproperty=value`
`-J<flag>`
`-P:<plugin>:<opt>`
`-V`
`-W`
`-X`
`-Y`
`-bootclasspath`
`-classpath`
`-d`
`-dependencyfile`
`-deprecation`
`-encoding`
`-explaintypes`	`-explain-types`
`-extdirs`
`-feature`
`-g`
`-help`
`-javabootclasspath`
`-javaextdirs`
`-language`
`-no-specialization`
`-nobootcp`
`-nowarn`
`-opt`
`-opt-inline-from`
`-opt-warnings`
`-optimize`
`-print`
`-release`
`-rootdir`
`-sourcepath`
`-target`	`-Xtarget`
`-toolcp`
`-unchecked`
`-uniqid`
`-usejavacp`
`-usemanifestc`
`-verbose`
`-version`

Verbose Settings

2.13.x	3.3.x
`-Vbrowse:<phases>`
`-Vclasspath`	`-Ylog-classpath`
`-Vdebug`	`-Ydebug`
`-Vdebug-tasty`
`-Vdebug-type-error`
`-Vdoc`
`-Vfree-terms`
`-Vfree-types`
`-Vhot-statistics`
`-Vide`
`-Vimplicit-conversions`
`-Vimplicits`
`-Vimplicits-max-refined`
`-Vimplicits-verbose-tree`
`-Vinline <package/Class.method>`
`-Vlog:<phases>`	`-Ylog:<phases>`
`-Vmacro`
`-Vmacro-lite`
`-Vopt <package/Class.method>`
`-Vpatmat`
`-Vphases`
`-Vpos`
`-Vprint:<phases>`
`-Vprint-args <file>`
`-Vprint-pos`	`-Yprint-pos`
`-Vprint-types`	`-Xprint-types`
`-Vquasiquote`
`-Vreflective-calls`
`-Vreify`
`-Vshow:<phases>`
`-Vshow-class <class>`
`-Vshow-member-pos <output style>`
`-Vshow-object <object>`
`-Vshow-symkinds`
`-Vshow-symowners`
`-Vstatistics <phases>`
`-Vsymbols`
`-Vtype-diffs`
`-Vtyper`

Warning Settings

2.13.x	3.3.x
`-Wconf`
`-Wdead-code`
`-Werror`
`-Wextra-implicit`
`-Wmacros:<mode>`
`-Wnonunit-if`
`-Wnonunit-statement`
`-Wnumeric-widen`
`-Woctal-literal`
`-Wopt`
`-Wperformance`
`-Wself-implicit`
`-Wunused:<warnings>`
`-Wvalue-discard`

Advanced Settings

2.13.x	3.3.x
`-Xasync`
`-Xcheckinit`	`-Ysafe-init`
`-Xdev`
`-Xdisable-assertions`
`-Xelide-below`
`-Xexperimental`
`-Xfuture`
`-Xgenerate-phase-graph`
`-Xjline`
`-Xlint:deprecation`	`-deprecation`
`-Xlint:<warnings>`
`-Xmacro-settings`
`-Xmain-class`
`-Xmaxerrs`
`-Xmaxwarns`
`-Xmigration`
`-Xmixin-force-forwarders`
`-Xno-forwarders`
`-Xno-patmat-analysis`
`-Xnon-strict-patmat-analysis`
`-Xnojline`
`-Xplugin`
`-Xplugin-disable`
`-Xplugin-list`
`-Xplugin-require`
`-Xpluginsdir`
`-Xprompt`
`-Xreporter`
`-Xresident`
`-Xscript`
`-Xsource`	`-source`
`-Xsource-reader`
`-Xverify`	`-Xverify-signatures`
`-Xxml`

Private settings

2.13.x	3.0.x
`-Ybackend-parallelism`
`-Ybackend-worker-queue`
`-Ybreak-cycles`
`-Ycache-macro-class-loader`
`-Ycache-plugin-class-loader`
`-Ycheck`
`-Ycompact-trees`
`-Ydelambdafy`
`-Ydump-classes`
`-Ygen-asmp`
`-Yimports`
`-Yissue-debug`
`-Yjar-compression-level`
`-YjarFactory`
`-Ymacro-annotations`
`-Ymacro-classpath`
`-Ymacro-expand`
`-Ymacro-global-fresh-names`
`-Yno-completion`
`-Yno-flat-classpath-cache`
`-Yno-generic-signatures`
`-Yno-imports`
`-Yno-predef`
`-Yopt-inline-heuristics`
`-Ypatmat-exhaust-depth`
`-Ypresentation-any-thread`
`-Ypresentation-debug`
`-Ypresentation-delay`
`-Ypresentation-locate-source-file`
`-Ypresentation-log`
`-Ypresentation-replay`
`-Ypresentation-strict`
`-Ypresentation-verbose`
`-Yprint-trees`
`-Yprofile-destination`
`-Yprofile-enabled`
`-Yprofile-external-tool`
`-Yprofile-run-gc`
`-Yprofile-trace`
`-Yrangepos`
`-Yrecursion`
`-Yreify-copypaste`
`-Yrepl-class-based`
`-Yrepl-outdir`
`-Yrepl-use-magic-imports`
`-Yresolve-term-conflict`
`-Yscala3-implicit-resolution`
`-Yscriptrunner`
`-Yskip`
`-Ystop-after`
`-Ystop-before`
`-Ytasty-no-annotations`
`-Ytasty-reader`
`-Ytrack-dependencies`
`-Yvalidate-pos`

Compiler Plugins

Some useful Scala 2.13 compiler plugins are now shipped into the compiler. You can enable and configure them with some new native options.

Scala.js

2.13.x	3.0.x
`-Xplugin:scalajs-compiler_<version>.jar`	`-scalajs`
`-P:scalajs:genStaticForwardersForNonTopLevelObjects`	`-scalajs-genStaticForwardersForNonTopLevelObjects`
`-P:scalajs:mapSourceURI`	`-scalajs-mapSourceURI`

SemanticDB

2.13.x	3.0.x
`-Xplugin:semanticdb-scalac_<version>.jar`	`-Xsemanticdb`
`-P:semanticdb:targetroot:<path>`	`-semanticdb-target:<path>`

Kind-Projector

2.13.x	3.0.x
`-Xplugin:kind-projector_<version>.jar`	`-Ykind-projector`

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