Scala Compiler2.13.18 < Back
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# Packages

-  package root

  The Scala compiler and reflection APIs.

  The Scala compiler and reflection APIs.

  Definition Classes
    root
-  package scala
  Definition Classes
    root
-  package tools
  Definition Classes
    scala
-  package nsc
  Definition Classes
    tools
-  package typechecker
  Definition Classes
    nsc
-  trait Contexts extends AnyRef

  Definition Classes
    typechecker
- Context
- ContextReporter
- ImportContext
- ImportInfo
- NoContext

c

scala.tools.nsc.typechecker.Contexts

# Context

###

#### class Context extends AnyRef

A motley collection of the state and loosely associated behaviour of the type checker. Each `Typer` has an associated context, and as it descends into the tree new `(Typer, Context)` pairs are spawned.

Meet the crew; first the state:

- A tree, symbol, and scope representing the focus of the typechecker
- An enclosing context, `outer`.
- The current compilation unit.
- A variety of bits that track the current error reporting policy (more on this later); whether or not implicits/macros are enabled, whether we are in a self or super call or in a constructor suffix. These are represented as bits in the mask `contextMode`.
- Some odds and ends: undetermined type parameters of the current line of type inference; contextual augmentation for error messages, tracking of the nesting depth.

And behaviour:

- The central point for issuing errors and warnings from the typechecker, with a means to buffer these for use in 'silent' type checking, when some recovery might be possible.

- `Context` is something of a Zipper for the tree were are typechecking: it `enclosingContextChain` is the path back to the root. This is exactly what we need to resolve names (`lookupSymbol`) and to collect in-scope implicit definitions (`implicitss`) Supporting these are `imports`, which represents all `Import` trees in in the enclosing context chain.
- In a similar vein, we can assess accessibility (`isAccessible`.)

More on error buffering: When are type errors recoverable? In quite a few places, it turns out. Some examples: trying to type an application with/without the expected type, or with/without implicit views enabled. This is usually mediated by `Typer.silent`, `Inferencer#tryTwice`.

Initially, starting from the `typer` phase, the contexts either buffer or report errors; afterwards errors are thrown. This is configured in `rootContext`. Additionally, more fine grained control is needed based on the kind of error; ambiguity errors are often suppressed during exploratory typing, such as determining whether `a == b` in an argument position is an assignment or a named argument, when `Inferencer#isApplicableSafe` type checks applications with and without an expected type, or when `Typer#tryTypedApply` tries to fit arguments to a function type with/without implicit views.

When the error policies entail error/warning buffering, the mutable ContextReporter records everything that is issued. It is important to note, that child Contexts created with `make` "inherit" the very same `ContextReporter` instance, whereas children spawned through `makeSilent` receive a separate, fresh buffer.

Source
  Contexts.scala

Linear Supertypes
AnyRef, Any
Known Subclasses
ImportContext, NoContext
Type Hierarchy
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Ordering

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2. By Inheritance

Inherited

1. Context
2. AnyRef
3. Any

Implicitly

1. by any2stringadd
2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

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Visibility

1. Public
2. Protected

### Type Members

1.  abstract class TryTwice extends AnyRef

   Try inference twice: once without views and once with views, unless views are already disabled.

### Value Members

1.  final def !=(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
2.  final def ##: Int
   Definition Classes
     AnyRef → Any
3.  def +(other: String): String
   Implicit
     This member is added by an implicit conversion from (Contexts.this)#Context toany2stringadd[(Contexts.this)#Context] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): ((Contexts.this)#Context, B)
   Implicit
     This member is added by an implicit conversion from (Contexts.this)#Context toArrowAssoc[(Contexts.this)#Context] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()
5.  final def ==(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
6.  def ambiguousErrors: Boolean
7.  def apply(mask: ContextMode): Boolean

   Is this context in all modes in the given `mask`?

8.  final def asInstanceOf[T0]: T0
   Definition Classes
     Any
9.  def bufferErrors: Boolean
10.  def clone(): AnyRef
    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.CloneNotSupportedException]) @native()
11.  var contextMode: ContextMode

    A bitmask containing all the boolean flags in a context, e.g.

    A bitmask containing all the boolean flags in a context, e.g. are implicit views enabled

12.  def defaultModeForTyped: Mode
13.  def defineByNameImplicit(tpe: Global.Type, result: (Contexts.this)#SearchResult): (Contexts.this)#SearchResult
14.  def deprecationWarning(pos: Global.Position, sym: Global.Symbol): Unit
15.  def deprecationWarning(pos: Global.Position, sym: Global.Symbol, msg: String, since: String, actions: List[CodeAction] = Nil): Unit
16.  val depth: Int
17.  def echo(pos: Global.Position, msg: String): Unit
18.  def emitImplicitDictionary(result: (Contexts.this)#SearchResult): (Contexts.this)#SearchResult
19.  var enclClass: (Contexts.this)#Context

    The next outer context whose tree is a template or package definition

20.  final def enclClassOrMethod: (Contexts.this)#Context

    The next enclosing context (potentially `this`) that is owned by a class or method

    The next enclosing context (potentially `this`) that is owned by a class or method

    Annotations
      @tailrec()
21.  var enclMethod: (Contexts.this)#Context

    The next (logical) outer context whose tree is a method.

    The next (logical) outer context whose tree is a method.

    NOTE: this is the "logical" enclosing method, which may not be the actual enclosing method when we synthesize a nested method, such as for lazy val getters (scala/bug#8245) or the methods that implement a PartialFunction literal (scala/bug#10291).

22.  def enclosingApply: (Contexts.this)#Context

    ...or an Apply.

23.  def enclosingCaseDef: (Contexts.this)#Context

    The next enclosing context (potentially `this`) that has a `CaseDef` as a tree

24.  def enclosingContextChain: List[(Contexts.this)#Context]
25.  final def enclosingImport: (Contexts.this)#Context
    Annotations
      @tailrec()
26.  def enclosingNonImportContext: (Contexts.this)#Context
27.  def enclosingSubClassContext(clazz: Global.Symbol): (Contexts.this)#Context

    Return the closest enclosing context that defines a subclass of `clazz` or a companion object thereof, or `NoContext` if no such context exists.

28.  def enrichmentEnabled: Boolean
29.  def enrichmentEnabled_=(value: Boolean): Unit
30.  def ensuring(cond: ((Contexts.this)#Context) => Boolean, msg: => Any): (Contexts.this)#Context
    Implicit
      This member is added by an implicit conversion from (Contexts.this)#Context toEnsuring[(Contexts.this)#Context] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
31.  def ensuring(cond: ((Contexts.this)#Context) => Boolean): (Contexts.this)#Context
    Implicit
      This member is added by an implicit conversion from (Contexts.this)#Context toEnsuring[(Contexts.this)#Context] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
32.  def ensuring(cond: Boolean, msg: => Any): (Contexts.this)#Context
    Implicit
      This member is added by an implicit conversion from (Contexts.this)#Context toEnsuring[(Contexts.this)#Context] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
33.  def ensuring(cond: Boolean): (Contexts.this)#Context
    Implicit
      This member is added by an implicit conversion from (Contexts.this)#Context toEnsuring[(Contexts.this)#Context] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
34.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
35.  def equals(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef → Any
36.  def error(pos: Global.Position, msg: String, actions: List[CodeAction] = Nil): Unit

    Issue/throw the given error message according to the current mode for error reporting.

37.  def extractUndetparams(): List[Global.Symbol]

    Return and clear the undetermined type parameters

38.  def featureWarning(pos: Global.Position, featureName: String, featureDesc: String, featureTrait: Global.Symbol, construct: => String = "", required: Boolean): Unit
39.  def finalize(): Unit
    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.Throwable])
40.  def firstImport: Option[(Contexts.this)#ImportInfo]

    Equivalent to `imports.headOption`, but more efficient

41.  def fixPosition(pos: Global.Position): Global.Position
42.  final def getClass(): Class[_ <: AnyRef]
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
43.  def hashCode(): Int
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
44.  final def implicitRootContext: (Contexts.this)#Context
    Annotations
      @tailrec()
45.  def implicitsEnabled: Boolean
46.  def implicitsEnabled_=(value: Boolean): Unit
47.  final def implicitss: List[List[(Contexts.this)#ImplicitInfo]]
48.  def importOrNull: (Contexts.this)#ImportInfo
    Attributes
      protected[Contexts]
49.  def imports: List[(Contexts.this)#ImportInfo]

    The currently visible imports, from innermost to outermost.

50.  def inAnnotation: Boolean
51.  def inConstructorSuffix: Boolean
52.  def inConstructorSuffix_=(value: Boolean): Unit
53.  def inPatAlternative: Boolean
54.  def inPatAlternative_=(value: Boolean): Unit
55.  def inReturnExpr: Boolean
56.  def inSecondTry: Boolean
57.  def inSecondTry_=(value: Boolean): Unit
58.  def inSelfSuperCall: Boolean
59.  def inSelfSuperCall_=(value: Boolean): Unit
60.  final def inSilentMode(expr: => Boolean): Boolean
    Annotations
      @inline()
61.  def inSuperInit: Boolean
62.  def inSuperInit_=(value: Boolean): Unit
63.  def inTypeConstructorAllowed: Boolean
64.  def initRootContext(throwing: Boolean = false, checking: Boolean = false): Unit

    Use reporter (possibly buffered) for errors/warnings and enable implicit conversion *

65.  def isAccessible(sym: Global.Symbol, pre: Global.Type, superAccess: Boolean = false): Boolean

    Is `sym` accessible as a member of `pre` in current context?

66.  def isInPackageObject(sym: Global.Symbol, pkg: Global.Symbol): Boolean

    Must `sym` defined in package object of package `pkg`, if it selected from a prefix with `pkg` as its type symbol?

67.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
68.  def isNameInScope(name: Global.Name): Boolean
69.  def isPackageOwnedInDifferentUnit(s: Global.Symbol): Boolean
70.  def isRootImport: Boolean

    A root import is never unused and always bumps context depth.

    A root import is never unused and always bumps context depth. (e.g scala._ / Predef._ and magic REPL imports)

71.  final def isSearchingForImplicitParam: Boolean
72.  final def javaFindMember(pre: Global.Type, name: Global.Name, qualifies: (Global.Symbol) => Boolean): (Global.Type, Global.Symbol)
73.  final def linkByNameImplicit(tpe: Global.Type): Global.Tree
74.  final def lookupCompanionInIncompleteOwner(original: Global.Symbol): Global.Symbol
75.  final def lookupSibling(original: Global.Symbol, name: Global.Name): Global.Symbol
76.  def lookupSymbol(name: Global.Name, qualifies: (Global.Symbol) => Boolean): Global.NameLookup
77.  def macrosEnabled: Boolean
78.  def macrosEnabled_=(value: Boolean): Unit
79.  def make(tree: Global.Tree, owner: Global.Symbol, scope: Global.Scope): (Contexts.this)#Context
80.  def make(tree: Global.Tree = tree, owner: Global.Symbol = owner, scope: Global.Scope = scope, unit: Global.CompilationUnit = unit, reporter: (Contexts.this)#ContextReporter = this.reporter): (Contexts.this)#Context

    Construct a child context.

    Construct a child context. The parent and child will share the report buffer. Compare with `makeSilent`, in which the child has a fresh report buffer.

    If `tree` is an `Import`, that import will be available at the head of `Context#imports`.

81.  def makeConstructorContext: (Contexts.this)#Context

    A context for typing constructor parameter ValDefs, super or self invocation arguments and default getters of constructors.

    A context for typing constructor parameter ValDefs, super or self invocation arguments and default getters of constructors. These expressions need to be type checked in a scope outside the class, cf. spec 5.3.1.

    This method is called by namer / typer where `this` is the context for the constructor DefDef. The owner of the resulting (new) context is the outer context for the Template, i.e. the context for the ClassDef. This means that class type parameters will be in scope. The value parameters of the current constructor are also entered into the new constructor scope. Members of the class however will not be accessible.

82.  def makeImplicit(reportAmbiguousErrors: Boolean): (Contexts.this)#Context

    Make a silent child context does not allow implicits.

    Make a silent child context does not allow implicits. Used to prevent chaining of implicit views.

83.  def makeImportContext(tree: Global.Import): (Contexts.this)#Context
84.  def makeNewScope(tree: Global.Tree, owner: Global.Symbol, reporter: (Contexts.this)#ContextReporter = this.reporter): (Contexts.this)#Context

    Make a child context that represents a new nested scope

85.  def makeNonSilent(newtree: Global.Tree): (Contexts.this)#Context
86.  def makeSilent(reportAmbiguousErrors: Boolean = ambiguousErrors, newtree: Global.Tree = tree): (Contexts.this)#Context

    Make a child context that buffers errors and warnings into a fresh report buffer.

87.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
88.  final def nextEnclosing(p: ((Contexts.this)#Context) => Boolean): (Contexts.this)#Context
    Annotations
      @tailrec()
89.  final def notify(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
90.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
91.  var openImplicits: List[(Contexts.this)#OpenImplicit]

    Types for which implicit arguments are currently searched

92.  final def outer: (Contexts.this)#Context
93.  def outerDepth: Int
    Attributes
      protected
94.  final def outermostContextAtCurrentPos: (Contexts.this)#Context
95.  val owner: Global.Symbol
96.  var pendingStabilizers: List[Global.Tree]
97.  var prefix: Global.Type
98.  def pushTypeBounds(sym: Global.Symbol): Unit
99.  final def refByNameImplicit(tpe: Global.Type): Global.Tree
100.  def reportErrors: Boolean
101.  def reporter: (Contexts.this)#ContextReporter
102.  final def resetCache(): Unit
     Annotations
       @tailrec()
103.  def restoreTypeBounds(tp: Global.Type): Global.Type
104.  def returnsSeen: Boolean
105.  def returnsSeen_=(value: Boolean): Unit
106.  def retyping: Boolean
107.  def retyping_=(value: Boolean): Unit
108.  var savedTypeBounds: List[(Global.Symbol, Global.Type)]

     Saved type bounds for type parameters which are narrowed in a GADT.

109.  def savingUndeterminedTypeParams[A](reportAmbiguous: Boolean = ambiguousErrors)(body: => A): A

     Run `body` with this context with no undetermined type parameters, restore the original the original list afterwards.

     Run `body` with this context with no undetermined type parameters, restore the original the original list afterwards.

     reportAmbiguous

       Should ambiguous errors be reported during evaluation of `body`?

110.  val scope: Global.Scope
111.  def set(enable: ContextMode = NOmode, disable: ContextMode = NOmode): Context.this.type

     Set all modes in the mask `enable` to true, and all in `disable` to false.

112.  def siteString: String
113.  def starPatterns: Boolean
114.  def starPatterns_=(value: Boolean): Unit
115.  final def synchronized[T0](arg0: => T0): T0
     Definition Classes
       AnyRef
116.  def toString(): String
     Definition Classes
       Context → AnyRef → Any
117.  val tree: Global.Tree
118.  def undetparams: List[Global.Symbol]

     Undetermined type parameters.

     Undetermined type parameters. See `Infer#{inferExprInstance, adjustTypeArgs}`. Not inherited to child contexts

119.  def undetparamsString: String
120.  def undetparams_=(ps: List[Global.Symbol]): Unit
121.  val unit: Global.CompilationUnit
122.  def update(mask: ContextMode, value: Boolean): Unit

     Update all modes in `mask` to `value`

123.  final def wait(): Unit
     Definition Classes
       AnyRef
     Annotations
       @throws(classOf[java.lang.InterruptedException])
124.  final def wait(arg0: Long, arg1: Int): Unit
     Definition Classes
       AnyRef
     Annotations
       @throws(classOf[java.lang.InterruptedException])
125.  final def wait(arg0: Long): Unit
     Definition Classes
       AnyRef
     Annotations
       @throws(classOf[java.lang.InterruptedException]) @native()
126.  def warning(pos: Global.Position, msg: String, category: WarningCategory, site: Global.Symbol): Unit
127.  def warning(pos: Global.Position, msg: String, category: WarningCategory, site: Global.Symbol, actions: List[CodeAction]): Unit
128.  def warning(pos: Global.Position, msg: String, category: WarningCategory, actions: List[CodeAction] = Nil): Unit

     Issue/throw the given error message according to the current mode for error reporting.

129.  final def withImplicits[T](enabled: Boolean)(op: => T): T
     Annotations
       @inline()
130.  final def withImplicitsDisabled[T](op: => T): T
     Annotations
       @inline()
131.  final def withImplicitsDisabledAllowEnrichment[T](op: => T): T
     Annotations
       @inline()
132.  final def withImplicitsEnabled[T](op: => T): T
     Annotations
       @inline()
133.  final def withMacros[T](enabled: Boolean)(op: => T): T
     Annotations
       @inline()
134.  final def withMacrosDisabled[T](op: => T): T
     Annotations
       @inline()
135.  final def withMacrosEnabled[T](op: => T): T
     Annotations
       @inline()
136.  final def withMode[T](enabled: ContextMode = NOmode, disabled: ContextMode = NOmode)(op: => T): T
     Annotations
       @inline()
137.  final def withOnlyStickyModes[T](op: => T): T
     Annotations
       @inline()
138.  final def withSuppressDeadArgWarning[T](suppress: Boolean)(op: => T): T
     Annotations
       @inline()
139.  final def withinAnnotation[T](op: => T): T
     Annotations
       @inline()
140.  final def withinPatAlternative[T](op: => T): T
     Annotations
       @inline()
141.  final def withinReturnExpr[T](op: => T): T
     Annotations
       @inline()
142.  final def withinSecondTry[T](op: => T): T
     Annotations
       @inline()
143.  final def withinStarPatterns[T](op: => T): T
     Annotations
       @inline()
144.  final def withinSuperInit[T](op: => T): T
     Annotations
       @inline()
145.  final def withinTypeConstructorAllowed[T](op: => T): T

     TypeConstructorAllowed is enabled when we are typing a higher-kinded type.

     TypeConstructorAllowed is enabled when we are typing a higher-kinded type. adapt should then check kind-arity based on the prototypical type's kind arity. Type arguments should not be inferred.

     Annotations
       @inline()

### Deprecated Value Members

1.  def formatted(fmtstr: String): String
   Implicit
     This member is added by an implicit conversion from (Contexts.this)#Context toStringFormat[(Contexts.this)#Context] performed by method StringFormat in scala.Predef.
   Definition Classes
     StringFormat
   Annotations
     @deprecated @inline()
   Deprecated

     (Since version 2.12.16) Use `formatString.format(value)` instead of `value.formatted(formatString)`, or use the `f""` string interpolator. In Java 15 and later, `formatted` resolves to the new method in String which has reversed parameters.

2.  def →[B](y: B): ((Contexts.this)#Context, B)
   Implicit
     This member is added by an implicit conversion from (Contexts.this)#Context toArrowAssoc[(Contexts.this)#Context] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @deprecated
   Deprecated

     (Since version 2.13.0) Use `->` instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from(Contexts.this)#Context to any2stringadd[(Contexts.this)#Context]

### Inherited by implicit conversion StringFormat from(Contexts.this)#Context to StringFormat[(Contexts.this)#Context]

### Inherited by implicit conversion Ensuring from(Contexts.this)#Context to Ensuring[(Contexts.this)#Context]

### Inherited by implicit conversion ArrowAssoc from(Contexts.this)#Context to ArrowAssoc[(Contexts.this)#Context]

### Ungrouped