Scalac 2.13 Options and Flags

Given that Scala 2.13
has just landed, there are a bunch of new flags and options available to the compiler. Below is a full list of options to choose from.

Standard Options

• -Dproperty=value
  Pass -Dproperty=value directly to the runtime system.
• -J
  <flag> Pass <flag> directly to the runtime system.
• -P
  :<plugin>:<opt> Pass an option to a plugin
• -V
  Print a synopsis of verbose options.
• -W
  Print a synopsis of warning options.
• -Werror
  Fail the compilation if there are any warnings.
• -X
  Print a synopsis of advanced options.
• -Y
  Print a synopsis of private options.
• -bootclasspath
  <path> Override location of bootstrap class files.
• -classpath
  <path> Specify where to find user class files.
• -d
  <directory|jar> destination for generated classfiles.
• -dependencyfile
  <file> Set dependency tracking file.
• -deprecation
  Emit warning and location for usages of deprecated APIs.
• -encoding
  <encoding> Specify character encoding used by source files.
• -explaintypes
  Explain type errors in more detail.
• -extdirs
  <path> Override location of installed extensions.
• -feature
  Emit warning and location for usages of features that should be imported explicitly.
• -g
  :<level> Set level of generated debugging info. (none,source,line,[vars],notailcalls)
• -help
  Print a synopsis of standard options
• -javabootclasspath
  <path> Override java boot classpath.
• -javaextdirs
  <path> Override java extdirs classpath.
• -language
  :<features> Enable or disable language features
• -no-specialization
  Ignore @specialize
  annotations.
• -nobootcp
  Do not use the boot classpath for the scala jars.
• -nowarn
  Generate no warnings.
• -opt
  :<optimizations> Enable optimizations
• -opt-inline-from
  :<patterns> Patterns for classfile names from which to allow inlining, help
  for details.
• -opt-warnings
  :<warnings> Enable optimizer warnings
• -print
  Print program with Scala-specific features removed.
• -release
  <release> Compile for a specific version of the Java platform. Supported targets: 6, 7, 8, 9
• -sourcepath
  <path> Specify location(s) of source files.
• -target
  :<target> Target platform for object files. All JVM 1.5 – 1.7 targets are deprecated. (jvm-1.5,jvm-1.6,jvm-1.7,[jvm-1.8])
• -toolcp
  <path> Add to the runner classpath.
• -unchecked
  Enable additional warnings where generated code depends on assumptions.
• -uniqid
  Uniquely tag all identifiers in debugging output.
• -usejavacp
  Utilize the java.class.path in classpath resolution.
• -usemanifestcp
  Utilize the manifest in classpath resolution.
• -verbose
  Output messages about what the compiler is doing.
• -version
  Print product version and exit.
• @
  <file> A text file containing compiler arguments (options and source files)

Deprecated settings:

• -optimize Enables optimizations. deprecated: Since 2.12, enables -opt:l:inline -opt-inline-from:**. See -opt:help.

Verbose Options (-V)

• -Vbrowse
  :<phases> Browse the abstract syntax tree after <phases>
• -Vclasspath
  Output information about what classpath is being applied.
• -Vdebug
  Increase the quantity of debugging output.
• -Vdoc
  Trace scaladoc activity.
• -Vfree-terms
  Print a message when reification creates a free term.
• -Vfree-types
  Print a message when reification resorts to generating a free type.
• -Vhot-statistics
  Enable -Vstatistics
  to also print hot statistics.
• -Vide
  Generate, validate and output trees using the interactive compiler.
• -Vimplicit-conversions
  Print a message whenever an implicit conversion is inserted.
• -Vimplicits
  Show more detail on why some implicits are not applicable.
• -Vinline
  <package/Class.method> Print a summary of inliner activity; _
  to print all, prefix match to select.
• -Vissue
  Print stack traces when a context issues an error.
• -Vlog
  :<phases> Log operations during <phases>
• -Vmacro
  Trace macro activities: compilation, generation of synthetics, classloading, expansion, exceptions.
• -Vmacro-lite
  Trace macro activities with less output.
• -Vopt
  <package/Class.method> Trace the optimizer progress for methods; _
  to print all, prefix match to select.
• -Vpatmat
  Trace pattern matching translation.
• -Vphases
  Print a synopsis of compiler phases.
• -Vpos
  Trace position validation.
• -Vprint
  :<phases> Print out program after <phases>
• -Vprint-args
  <file> Print all compiler arguments to the specified location. Use – to echo to the reporter.
• -Vprint-pos
  Print tree positions, as offsets.
• -Vprint-types
  Print tree types (debugging option).
• -Vquasiquote
  Trace quasiquotations.
• -Vreflective-calls
  Print a message when a reflective method call is generated
• -Vreify
  Trace reification.
• -Vshow
  :<phases> (Requires -Xshow-class or -Xshow-object) Show after <phases>
• -Vshow-class
  <class> Show internal representation of class.
• -Vshow-member-pos
  <output style> Show start and end positions of members (implies -Yrangepos)
• -Vshow-object
  <object> Show internal representation of object.
• -Vshow-symkinds
  Print abbreviated symbol kinds next to symbol names.
• -Vshow-symowners
  Print owner identifiers next to symbol names.
• -Vstatistics
  [:phases] Print compiler statistics for specific phases <phases> (default: parser,typer,patmat,erasure,cleanup,jvm)
• -Vsymbols
  Print the AST symbol hierarchy after each phase.
• -Vtyper
  Trace type assignments.
• Note
  :
  • Boolean settings are false unless set: -Xdev -Xcheck-init:true -Xprompt:false
  • Multi-valued settings are comma-separated: -Xlint:infer-any,unused,-missing-interpolator
  • Phases are a list of names, ids, or ranges of ids: -Xprint:parser,typer,5-10 -Ylog:-4_
  • Use _ to enable all: -language:_ -Xprint:_

Advanced Options (-X)

• -Xcheckinit
  Wrap field accessors to throw an exception on uninitialized access.
• -Xdev
  Indicates user is a developer – issue warnings about anything which seems amiss
• -Xdisable-assertions
  Generate no assertions or assumptions.
• -Xelide-below
  <n> Calls to @elidable
  methods are omitted if method priority is lower than argument
• -Xgenerate-phase-graph
  <file> Generate the phase graphs (outputs .dot files) to fileX.dot.
• -Xlint
  :<warnings> Enable recommended warnings
• -Xmacro-settings
  :<option> Custom settings for macros.
• -Xmain-class
  <path> Class for manifest’s Main-Class entry (only useful with -d <jar>)
• -Xmaxerrs
  <n> Maximum errors to print
• -Xmaxwarns
  <n> Maximum warnings to print
• -Xmigration
  :<version> Warn about constructs whose behavior may have changed since version.
• -Xmixin-force-forwarders
  :<mode> Generate forwarder methods in classes inhering concrete methods from traits. Default: true
  , help
  to list choices.
• -Xno-forwarders
  Do not generate static forwarders in mirror classes.
• -Xno-patmat-analysis
  Don’t perform exhaustivity/unreachability analysis. Also, ignore @switch
  annotation.
• -Xno-uescape
  Disable handling of nicode escapes.
• -Xnojline
  Do not use JLine for editing.
• -Xplugin
  :<paths> Load a plugin from each classpath.
• -Xplugin-disable
  :<plugin> Disable plugins by name.
• -Xplugin-list
  Print a synopsis of loaded plugins.
• -Xplugin-require
  :<plugin> Abort if a named plugin is not loaded.
• -Xpluginsdir
  <path> Path to search for plugin archives.
• -Xprompt
  Display a prompt after each error (debugging option).
• -Xreporter
  <classname> Specify a custom reporter for compiler messages.
• -Xresident
  Compiler stays resident: read source filenames from standard input.
• -Xscript
  <object> Treat the source file as a script and wrap it in a main method.
• -Xsource
  :<version> Treat compiler input as Scala source for the specified version, see scala/bug#8126
  .
• -Xsource-reader
  <classname> Specify a custom method for reading source files.
• -Xverify
  Verify generic signatures in generated bytecode.
• -Xxml
  :<propertys> Configure XML parsing.

Private Options (-Y)

• -Ybackend-parallelism
  <n> maximum worker threads for backend
• -Ybackend-worker-queue
  <n> backend threads worker queue size
• -Ybreak-cycles
  Attempt to break cycles encountered during typing
• -Ycache-macro-class-loader
  :<policy> Policy for caching class loaders for macros that are dynamically loaded. Default: none
  , help
  to list choices.
• -Ycache-plugin-class-loader
  :<policy> Policy for caching class loaders for compiler plugins that are dynamically loaded. Default: none
  , help
  to list choices.
• -Ycheck
  :<phases> Check the tree at the end of <phases>
• -Ycompact-trees
  Use compact tree printer when displaying trees.
• -Ydelambdafy
  :<strategy> Strategy used for translating lambdas into JVM code. (inline,[method])
• -Ydump-classes
  <dir> Dump the generated bytecode to .class files (useful for reflective compilation that utilizes in-memory classloaders).
• -Ygen-asmp
  <dir> Generate a parallel output directory of .asmp files (ie ASM Textifier output).
• -Yimports
  :<import> Custom root imports, default is java.lang,scala,scala.Predef
  .
• -Yjar-compression-level
  <n> compression level to use when writing jar files
• -Ymacro-annotations
  Enable support for macro annotations, formerly in macro paradise.
• -Ymacro-classpath
  <path> The classpath used to reflectively load macro implementations, default is the compilation classpath.
• -Ymacro-expand
  :<policy> Control expansion of macros, useful for scaladoc and presentation compiler. ([normal],none,discard)
• -Ymacro-global-fresh-names
  Should fresh names in macros be unique across all compilation units
• -Yno-completion
  Disable tab-completion in the REPL.
• -Yno-flat-classpath-cache
  Do not cache flat classpath representation of classpath elements from jars across compiler instances.
• -Yno-generic-signatures
  Suppress generation of generic signatures for Java.
• -Yno-imports
  Compile without importing scala. , java.lang.
  , or Predef.
• -Yno-predef
  Compile without importing Predef.
• -Yopt-inline-heuristics
  :<strategy> Set the heuristics for inlining decisions. (at-inline-annotated,everything,[default])
• -Ypatmat-exhaust-depth
  <n> off
• -Ypresentation-any-thread
  Allow use of the presentation compiler from any thread
• -Ypresentation-debug
  Enable debugging output for the presentation compiler.
• -Ypresentation-delay
  <n> Wait number of ms after typing before starting typechecking
• -Ypresentation-log
  <file> Log presentation compiler events into file
• -Ypresentation-replay
  <file> Replay presentation compiler events from file
• -Ypresentation-strict
  Do not report type errors in sources with syntax errors.
• -Ypresentation-verbose
  Print information about presentation compiler tasks.
• -Yprint-trees
  :<style> How to print trees when -Xprint is enabled. ([text],compact,format,text+format)
• -Yprofile-destination
  <file> Profiling output – specify a file or -
  for console.
• -Yprofile-enabled
  Enable profiling.
• -Yprofile-external-tool
  [:phases] Enable profiling for a phase using an external tool hook. Generally only useful for a single phase <phases> (default: typer)
• -Yprofile-run-gc
  [:phases] Run a GC between phases – this allows heap size to be accurate at the expense of more time. Specify a list of phases, or all <phases> (default: _)
• -Yprofile-trace
  <file> Capture trace of compilation in Chrome Trace format
• -Yrangepos
  Use range positions for syntax trees.
• -Yrecursion
  <n> Set recursion depth used when locking symbols.
• -Yreify-copypaste
  Dump the reified trees in copypasteable representation.
• -Yrepl-class-based
  Use classes to wrap REPL snippets instead of objects
• -Yrepl-outdir
  <path> Write repl-generated classfiles to given output directory (use “” to generate a temporary dir)
• -Yresolve-term-conflict
  :<strategy> Resolve term conflicts. (package,object,[error])
• -Yscriptrunner
  <classname> Specify a scala.tools.nsc.ScriptRunner (default, resident, shutdown, or a class name).
• -Yskip
  :<phases> Skip <phases>
• -Ystop-after
  :<phases> Stop after <phases>
• -Ystop-before
  :<phases> Stop before <phases>
• -Yvalidate-pos
  :<phases> Validate positions after the given phases (implies -Yrangepos) <phases>
• Note
  :
  • Boolean settings are false unless set: -Xdev -Xcheck-init:true -Xprompt:false
  • Multi-valued settings are comma-separated: -Xlint:infer-any,unused,-missing-interpolator
  • Phases are a list of names, ids, or ranges of ids: -Xprint:parser,typer,5-10 -Ylog:-4
  • Use _ to enable all: -language:_ -Xprint:_

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