Edit

ExplicitResultTypes

This rewrite inserts type annotations for inferred public members. Only compatible with scala 2.12 & 2.13.

Example:

- def myComplexMethod = 1.to(10).map(i => i -> i.toString).toMap
+ def myComplexMethod: Map[Int, String] = 1.to(10).map(i => i -> i.toString).toMap

Configuration

By default, only rewrite adds type annotations for public members that have non-trivial bodies.

NameTypeDescription
memberKindList[MemberKind]Enable/disable this rule for defs, vals or vars.
memberVisibilityList[MemberVisibility]Enable/disable this rule for private/protected members.
skipSimpleDefinitionsSimpleDefinitionsIf false, insert explicit result types even for simple definitions like `val x = 2`
fatalWarningsBooleanIf true, report and fail unexpected errors. If false, silently ignore errors to produce an explicit result type.
rewriteStructuralTypesToNamedSubclassBooleanIf false, disables rewriting of inferred structural types to named subclasses. Beware that this option may produce code that no longer compiles if it previously used `scala.language.reflectiveCalls` to access methods on structural types.
onlyImplicitsBooleanIf true, adds result types only to implicit definitions.

Defaults

ExplicitResultTypes.memberKind = [
  Def,
  Val,
  Var
]
ExplicitResultTypes.memberVisibility = [
  Public,
  Protected
]
ExplicitResultTypes.skipSimpleDefinitions = ['Term.Ref', 'Lit', 'Term.New']
ExplicitResultTypes.fatalWarnings = false
ExplicitResultTypes.rewriteStructuralTypesToNamedSubclass = true
ExplicitResultTypes.onlyImplicits = false

Examples

ExplicitResultTypes.memberKind = [Def, Val, Var]
ExplicitResultTypes.memberVisibility = [Public, Protected]
ExplicitResultTypes.skipSimpleDefinitions = ['Lit', 'Term.New']

Known limitations

This rule has several known limitations, which are most likely fixable with some effort. At the time of this writing, there are no short-term plans to address these issues however.

Imports ordering

The rewrite inserts imports at the bottom of the global import list. Users are expected to organize the imports according to the conventions of their codebase.

For example, the rewrite may produce the following diff.

import java.io.File
import scala.collection.mutable
+ import java.util.UUID

Potential workarounds:

← DisableSyntaxLeakingImplicitClassVal →