Per-file change stats of the migration

gistfile1.txt

```
370 ++++++++++----------- .../tools/backend/jvm/DottyBackendInterface.scala
208 ++++++------ compiler/src/dotty/tools/dotc/core/Types.scala
148 ++++----- .../dotty/tools/backend/jvm/BCodeSkelBuilder.scala
138 ++++---- compiler/src/dotty/tools/dotc/core/Scopes.scala
86 +++-- compiler/src/dotty/tools/dotc/sbt/ExtractAPI.scala
71 ++-- .../src/dotty/tools/dotc/util/WeakHashSet.scala
68 ++-- .../src/dotty/tools/backend/jvm/GenBCode.scala
66 ++-- compiler/src/dotty/tools/dotc/core/Contexts.scala
63 ++-- .../src/dotty/tools/dotc/core/SymDenotations.scala
60 ++-- compiler/src/dotty/tools/dotc/sbt/ShowAPI.scala
52 ++- .../src/dotty/tools/dotc/typer/Implicits.scala
51 ++- .../src/dotty/tools/dotc/core/TypeComparer.scala
49 ++- .../dotty/tools/dotc/util/SimpleIdentityMap.scala
49 ++- .../dotty/tools/backend/jvm/BCodeBodyBuilder.scala
47 ++- .../dotty/tools/dotc/core/OrderingConstraint.scala
46 ++- .../dotc/core/unpickleScala2/Scala2Unpickler.scala
42 ++- compiler/src/dotty/tools/dotc/core/Names.scala
41 ++- compiler/src/dotty/tools/dotc/core/Symbols.scala
40 ++- .../src/dotty/tools/dotc/parsing/Parsers.scala
38 +-- compiler/src/dotty/tools/backend/jvm/BTypes.scala
38 +-- .../src/dotty/tools/dotc/typer/ImportInfo.scala
37 +-- .../dotty/tools/backend/jvm/BackendInterface.scala
33 +- compiler/src/dotty/tools/io/AbstractFile.scala
31 +- compiler/src/dotty/tools/io/Jar.scala
30 +- compiler/src/dotty/tools/repl/ScriptEngine.scala
29 +- compiler/src/dotty/tools/io/ZipArchive.scala
29 +- compiler/src/dotty/tools/io/Path.scala
29 +- compiler/src/dotty/tools/dotc/core/Hashable.scala
28 +- .../src/dotty/tools/dotc/typer/ConstFold.scala
28 +- .../src/dotty/tools/backend/sjs/JSCodeGen.scala
27 +- compiler/src/dotty/tools/dotc/Run.scala
27 +- .../src/dotty/tools/dotc/config/Properties.scala
26 +- .../dotc/core/classfile/ClassfileParser.scala
24 -- tests/neg/explicit-null-alias.scala
24 +- .../src/dotty/tools/dotc/typer/Applications.scala
24 +- .../src/dotty/tools/dotc/parsing/Scanners.scala
23 +- compiler/src/dotty/tools/dotc/core/Uniques.scala
23 +- .../tools/dotc/classpath/DirectoryClassPath.scala
22 +- .../src/dotty/tools/dotc/core/TyperState.scala
22 +- .../dotty/tools/backend/jvm/BCodeSyncAndTry.scala
20 +- compiler/src/dotty/tools/dotc/typer/Namer.scala
20 +- .../tools/dotc/transform/OverridingPairs.scala
19 +- .../src/dotty/tools/dotc/core/Substituters.scala
19 +- .../dotc/parsing/xml/SymbolicXMLBuilder.scala
17 +- .../src/dotty/tools/dotc/typer/ProtoTypes.scala
16 +- .../dotty/tools/backend/jvm/BytecodeWriters.scala
15 +- .../tools/dotc/core/tasty/TreeUnpickler.scala
15 +- .../src/dotty/tools/dotc/core/TypeErrors.scala
14 +- compiler/src/dotty/tools/dotc/ast/Trees.scala
14 +- .../tools/dotc/transform/PatternMatcher.scala
14 +- .../src/dotty/tools/dotc/util/Attachment.scala
14 +- .../src/dotty/tools/dotc/transform/LazyVals.scala
14 +- .../src/dotty/tools/dotc/parsing/xml/Utility.scala
14 +- .../reporting/diagnostic/MessageContainer.scala
14 +- .../dotty/tools/dotc/transform/ReifyQuotes.scala
14 +- .../dotc/classpath/VirtualDirectoryClassPath.scala
13 - tests/neg/explicit-null-type-arg.scala
13 +- .../tools/dotc/classpath/ClassPathFactory.scala
13 +- .../src/dotty/tools/backend/jvm/BCodeHelpers.scala
12 +- .../tools/dotc/interactive/InteractiveDriver.scala
12 +- .../src/dotty/tools/dotc/profile/Profiler.scala
12 +- .../dotty/tools/dotc/reporting/StoreReporter.scala
12 +- .../dotc/decompiler/DecompilationPrinter.scala
12 +- .../classpath/ZipAndJarFileLookupFactory.scala
11 +- compiler/src/dotty/tools/io/NoAbstractFile.scala
11 +- .../src/dotty/tools/dotc/core/Decorators.scala
11 +- .../dotty/tools/dotc/sbt/ExtractDependencies.scala
11 +- .../dotty/tools/dotc/core/ConstraintRunInfo.scala
11 +- .../dotty/tools/backend/jvm/BCodeIdiomatic.scala
10 - tests/pos/explicit-null-option-ornull.scala
10 +- compiler/src/dotty/tools/io/VirtualDirectory.scala
10 +- compiler/src/dotty/tools/dotc/core/Phases.scala
10 +- compiler/src/dotty/tools/dotc/ast/tpd.scala
10 +- compiler/src/dotty/tools/dotc/Driver.scala
10 +- .../tools/dotc/reporting/MessageRendering.scala
10 +- .../src/dotty/tools/dotc/typer/RefChecks.scala
10 +- .../src/dotty/tools/dotc/typer/Inferencing.scala
10 +- .../src/dotty/tools/dotc/core/SymbolLoaders.scala
10 +- .../src/dotty/tools/backend/sjs/JSPositions.scala
9 - .../src-non-bootstrapped/scala/ExplicitNulls.scala
9 +- compiler/src/dotty/tools/io/File.scala
9 +- .../src/dotty/tools/dotc/core/Denotations.scala
9 +- .../src/dotty/tools/dotc/core/Annotations.scala
8 +- library/src/dotty/runtime/LazyVals.scala
8 +- compiler/src/dotty/tools/dotc/util/HashSet.scala
8 +- compiler/src/dotty/tools/dotc/typer/Typer.scala
8 +- .../tools/dotc/config/WrappedProperties.scala
8 +- .../src/dotty/tools/dotc/transform/Splicer.scala
8 +- .../src/dotty/tools/dotc/transform/MegaPhase.scala
8 +- .../src/dotty/tools/dotc/quoted/QuoteDriver.scala
8 +- .../src/dotty/tools/dotc/fromtasty/Debug.scala
8 +- .../dotty/tools/dotc/transform/MoveStatics.scala
8 +- .../dotc/classpath/ZipArchiveFileLookup.scala
7 +- compiler/src/dotty/tools/repl/JLineTerminal.scala
7 +- compiler/src/dotty/tools/io/Directory.scala
7 +- .../src/dotty/tools/dotc/core/Definitions.scala
6 +- compiler/src/dotty/tools/dotc/typer/Inliner.scala
6 +- compiler/src/dotty/tools/dotc/plugins/Plugin.scala
6 +- compiler/src/dotty/tools/dotc/core/JavaNull.scala
6 +- .../tools/dotc/printing/SyntaxHighlighting.scala
6 +- .../tools/dotc/core/tasty/DottyUnpickler.scala
6 +- .../tools/dotc/core/quoted/PickledQuotes.scala
6 +- .../src/dotty/tools/dotc/util/SourceFile.scala
6 +- .../src/dotty/tools/dotc/config/OutputDirs.scala
6 +- .../dotty/tools/dotc/transform/patmat/Space.scala
6 +- .../dotty/tools/dotc/transform/CapturedVars.scala
6 +- .../dotty/tools/dotc/interactive/Completion.scala
5 +- library/src/scala/runtime/EnumValues.scala
5 +- library/src/scala/TupleXXL.scala
5 +- compiler/src/dotty/tools/repl/Rendering.scala
5 +- compiler/src/dotty/tools/io/VirtualFile.scala
5 +- compiler/src/dotty/tools/dotc/core/TypeOps.scala
5 +- .../src/dotty/tools/dotc/core/TypeErasure.scala
5 +- .../src/dotty/tools/dotc/config/PathResolver.scala
5 +- .../dotty/tools/repl/AbstractFileClassLoader.scala
5 +- .../dotty/tools/backend/jvm/BCodeAsmCommon.scala
4 - library/src-bootstrapped/scala/ExplicitNulls.scala
4 +- compiler/src/dotty/tools/io/ClassPath.scala
4 +- compiler/src/dotty/tools/dotc/util/DiffUtil.scala
4 +- compiler/src/dotty/tools/dotc/core/Constants.scala
4 +- compiler/src/dotty/tools/dotc/ast/untpd.scala
4 +- compiler/src/dotty/tools/dotc/ast/Positioned.scala
4 +- compiler/src/dotty/tools/dotc/ast/Desugar.scala
4 +- .../tools/dotc/transform/TypeTestsCasts.scala
4 +- .../tools/dotc/transform/SuperAccessors.scala
4 +- .../tools/dotc/transform/GenericSignatures.scala
4 +- .../tools/dotc/tastyreflect/PositionOpsImpl.scala
4 +- .../tools/dotc/tastyreflect/ContextOpsImpl.scala
4 +- .../tools/dotc/reporting/diagnostic/messages.scala
4 +- .../tools/dotc/reporting/diagnostic/Message.scala
4 +- .../tools/dotc/classpath/AggregateClassPath.scala
4 +- .../src/dotty/tools/dotc/util/SourcePosition.scala
4 +- .../src/dotty/tools/dotc/transform/Flatten.scala
4 +- .../src/dotty/tools/dotc/transform/Erasure.scala
4 +- .../src/dotty/tools/dotc/sbt/ThunkHolder.scala
4 +- .../src/dotty/tools/dotc/printing/Formatting.scala
4 +- .../src/dotty/tools/dotc/parsing/JavaParsers.scala
4 +- .../src/dotty/tools/dotc/config/Settings.scala
4 +- .../src/dotty/tools/dotc/CompilationUnit.scala
4 +- .../src/dotty/tools/backend/sjs/ScopedVar.scala
4 +- .../dotty/tools/dotc/transform/AccessProxies.scala
4 +- .../dotty/tools/dotc/fromtasty/TastyFileUtil.scala
4 +- .../dotty/tools/dotc/core/tasty/TreePickler.scala
4 +- .../dotty/tools/dotc/core/tasty/TastyString.scala
4 +- .../dotc/decompiler/IDEDecompilerDriver.scala
3 +- compiler/src/dotty/tools/repl/ReplDriver.scala
3 +- compiler/src/dotty/tools/io/PlainFile.scala
3 +- compiler/src/dotty/tools/io/JarArchive.scala
3 +- compiler/src/dotty/tools/dotc/util/LRUCache.scala
3 +- .../tools/dotc/parsing/xml/MarkupParsers.scala
3 +- .../src/dotty/tools/dotc/plugins/Plugins.scala
3 +- .../src/dotty/tools/dotc/classpath/FileUtils.scala
3 +- .../src/dotty/tools/backend/jvm/AsmUtils.scala
3 +- .../dotc/transform/CollectNullableFields.scala
2 +- project/Build.scala
1 - compiler/src/dotty/tools/dotc/core/FlowFacts.scala
```