Scala Compiler2.12.2 < 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
  Version

    1.0

- 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 ReportBuffer records everything that is issued. It is important to note, that child Contexts created with `make` "inherit" the very same `ReportBuffer` 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

1. Alphabetic
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. All

### 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 Analyzer.Context to any2stringadd[Analyzer.Context] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (Analyzer.Context, B)
   Implicit
     This member is added by an implicit conversion from Analyzer.Context to ArrowAssoc[Analyzer.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[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
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 deprecationWarning(pos: Global.Position, sym: Global.Symbol): Unit
14.  def deprecationWarning(pos: Global.Position, sym: Global.Symbol, msg: String, since: String): Unit
15.  val depth: Int
16.  var diagUsedDefaults: Boolean

    To enrich error messages involving default arguments.

    To enrich error messages involving default arguments. When extending the notion, group diagnostics in an object.

17.  def echo(pos: Global.Position, msg: String): Unit
18.  var enclClass: Analyzer.Context

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

19.  def enclClassOrMethod: Analyzer.Context

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

20.  var enclMethod: Analyzer.Context

    The next outer context whose tree is a method

21.  def enclosingApply: Analyzer.Context

    ...or an Apply.

22.  def enclosingCaseDef: Analyzer.Context

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

23.  def enclosingContextChain: List[Analyzer.Context]
24.  def enclosingNonImportContext: Analyzer.Context
25.  def enclosingSubClassContext(clazz: Global.Symbol): Analyzer.Context

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

26.  def enrichmentEnabled: Boolean
27.  def enrichmentEnabled_=(value: Boolean): Unit
28.  def ensuring(cond: (Analyzer.Context) ⇒ Boolean, msg: ⇒ Any): Analyzer.Context
    Implicit
      This member is added by an implicit conversion from Analyzer.Context to Ensuring[Analyzer.Context] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
29.  def ensuring(cond: (Analyzer.Context) ⇒ Boolean): Analyzer.Context
    Implicit
      This member is added by an implicit conversion from Analyzer.Context to Ensuring[Analyzer.Context] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
30.  def ensuring(cond: Boolean, msg: ⇒ Any): Analyzer.Context
    Implicit
      This member is added by an implicit conversion from Analyzer.Context to Ensuring[Analyzer.Context] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
31.  def ensuring(cond: Boolean): Analyzer.Context
    Implicit
      This member is added by an implicit conversion from Analyzer.Context to Ensuring[Analyzer.Context] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
32.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
33.  def equals(arg0: Any): Boolean
    Definition Classes
      AnyRef → Any
34.  def error(pos: Global.Position, msg: String): Unit

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

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

    Return and clear the undetermined type parameters

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

    Equivalent to `imports.headOption`, but more efficient

39.  def fixPosition(pos: Global.Position): Global.Position
40.  def formatted(fmtstr: String): String
    Implicit
      This member is added by an implicit conversion from Analyzer.Context to StringFormat[Analyzer.Context] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()
41.  final def getClass(): Class[_]
    Definition Classes
      AnyRef → Any
42.  def hashCode(): Int
    Definition Classes
      AnyRef → Any
43.  def implicitsEnabled: Boolean
44.  def implicitsEnabled_=(value: Boolean): Unit
45.  def implicitss: List[List[Analyzer.ImplicitInfo]]
46.  def imports: List[Analyzer.ImportInfo]

    The currently visible imports

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

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

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

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

62.  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?

63.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
64.  def isNameInScope(name: Global.Name): Boolean
65.  def isRootImport: Boolean
66.  def lookup(name: Global.Name, expectedOwner: Global.Symbol): Global.Symbol

    Find a symbol in this context or one of its outers.

    Find a symbol in this context or one of its outers.

    Used to find symbols are owned by methods (or fields), they can't be found in some scope.

    Examples: companion module of classes owned by a method, default getter methods of nested methods. See NamesDefaults.scala

67.  final def lookupCompanionInIncompleteOwner(original: Global.Symbol): Global.Symbol
68.  def lookupSymbol(name: Global.Name, qualifies: (Global.Symbol) ⇒ Boolean): Global.NameLookup

    Find the symbol of a simple name starting from this context.

    Find the symbol of a simple name starting from this context. All names are filtered through the "qualifies" predicate, the search continuing as long as no qualifying name is found.

69.  def macrosEnabled: Boolean
70.  def macrosEnabled_=(value: Boolean): Unit
71.  def make(tree: Global.Tree, owner: Global.Symbol, scope: Global.Scope): Analyzer.Context
72.  def make(tree: Global.Tree = tree, owner: Global.Symbol = owner, scope: Global.Scope = scope, unit: Global.CompilationUnit = unit, reporter: Analyzer.ContextReporter = this.reporter): Analyzer.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`.

73.  def makeConstructorContext: Analyzer.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.

74.  def makeImplicit(reportAmbiguousErrors: Boolean): Analyzer.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.

75.  def makeNewScope(tree: Global.Tree, owner: Global.Symbol, reporter: Analyzer.ContextReporter = this.reporter): Analyzer.Context

    Make a child context that represents a new nested scope

76.  def makeNonSilent(newtree: Global.Tree): Analyzer.Context
77.  def makeSilent(reportAmbiguousErrors: Boolean = ambiguousErrors, newtree: Global.Tree = tree): Analyzer.Context

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

78.  var namedApplyBlockInfo: Option[(Global.Tree, Analyzer.NamedApplyInfo)]
79.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
80.  def nextEnclosing(p: (Analyzer.Context) ⇒ Boolean): Analyzer.Context
81.  final def notify(): Unit
    Definition Classes
      AnyRef
82.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
83.  var openImplicits: List[Analyzer.OpenImplicit]

    Types for which implicit arguments are currently searched

84.  final def outer: Analyzer.Context
85.  def outerDepth: Int
    Attributes
      protected
86.  val owner: Global.Symbol
87.  var prefix: Global.Type
88.  def pushTypeBounds(sym: Global.Symbol): Unit
89.  def reportErrors: Boolean
90.  def reporter: Analyzer.ContextReporter
91.  def resetCache(): Unit
92.  def restoreTypeBounds(tp: Global.Type): Global.Type
93.  def returnsSeen: Boolean
94.  def returnsSeen_=(value: Boolean): Unit
95.  def retyping: Boolean
96.  def retyping_=(value: Boolean): Unit
97.  var savedTypeBounds: List[(Global.Symbol, Global.Type)]

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

98.  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`?

99.  val scope: Global.Scope
100.  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.

101.  def siteString: String
102.  def starPatterns: Boolean
103.  def starPatterns_=(value: Boolean): Unit
104.  final def synchronized[T0](arg0: ⇒ T0): T0
     Definition Classes
       AnyRef
105.  def toString(): String
     Definition Classes
       Context → AnyRef → Any
106.  val tree: Global.Tree
107.  def undetparams: List[Global.Symbol]

     Undetermined type parameters.

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

108.  def undetparamsString: String
109.  def undetparams_=(ps: List[Global.Symbol]): Unit
110.  val unit: Global.CompilationUnit
111.  def update(mask: ContextMode, value: Boolean): Unit

     Update all modes in `mask` to `value`

112.  var variance: Variance

     Variance relative to enclosing class

113.  final def wait(): Unit
     Definition Classes
       AnyRef
     Annotations
       @throws( ... )
114.  final def wait(arg0: Long, arg1: Int): Unit
     Definition Classes
       AnyRef
     Annotations
       @throws( ... )
115.  final def wait(arg0: Long): Unit
     Definition Classes
       AnyRef
     Annotations
       @throws( ... )
116.  def warning(pos: Global.Position, msg: String): Unit

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

117.  final def withImplicits[T](enabled: Boolean)(op: ⇒ T): T
     Annotations
       @inline()
118.  final def withImplicitsDisabled[T](op: ⇒ T): T
     Annotations
       @inline()
119.  final def withImplicitsDisabledAllowEnrichment[T](op: ⇒ T): T
     Annotations
       @inline()
120.  final def withImplicitsEnabled[T](op: ⇒ T): T
     Annotations
       @inline()
121.  final def withMacros[T](enabled: Boolean)(op: ⇒ T): T
     Annotations
       @inline()
122.  final def withMacrosDisabled[T](op: ⇒ T): T
     Annotations
       @inline()
123.  final def withMacrosEnabled[T](op: ⇒ T): T
     Annotations
       @inline()
124.  final def withMode[T](enabled: ContextMode = NOmode, disabled: ContextMode = NOmode)(op: ⇒ T): T
     Annotations
       @inline()
125.  final def withOnlyStickyModes[T](op: ⇒ T): T
     Annotations
       @inline()
126.  final def withinPatAlternative[T](op: ⇒ T): T
     Annotations
       @inline()
127.  final def withinReturnExpr[T](op: ⇒ T): T
     Annotations
       @inline()
128.  final def withinSecondTry[T](op: ⇒ T): T
     Annotations
       @inline()
129.  final def withinStarPatterns[T](op: ⇒ T): T
     Annotations
       @inline()
130.  final def withinSuperInit[T](op: ⇒ T): T
     Annotations
       @inline()
131.  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()
132.  def →[B](y: B): (Analyzer.Context, B)
     Implicit
       This member is added by an implicit conversion from Analyzer.Context to ArrowAssoc[Analyzer.Context] performed by method ArrowAssoc in scala.Predef.
     Definition Classes
       ArrowAssoc

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from Analyzer.Context to any2stringadd[Analyzer.Context]

### Inherited by implicit conversion StringFormat from Analyzer.Context to StringFormat[Analyzer.Context]

### Inherited by implicit conversion Ensuring from Analyzer.Context to Ensuring[Analyzer.Context]

### Inherited by implicit conversion ArrowAssoc from Analyzer.Context to ArrowAssoc[Analyzer.Context]

### Ungrouped