scala.tools.nsc.typechecker.Contexts

# Context

###
Related Doc: package Contexts

#### 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

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AnyRef, Any
Known Subclasses
ImportContext, NoContext
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1. Context
2. AnyRef
3. Any

Implicitly

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

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### 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

   Test two objects for inequality.

   Test two objects for inequality.

   returns

     `true` if !(this == that), false otherwise.

   Definition Classes
     AnyRef → Any

2. #### final def ##(): Int

   Equivalent to `x.hashCode` except for boxed numeric types and `null`.

   Equivalent to `x.hashCode` except for boxed numeric types and `null`. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For `null` returns a hashcode where `null.hashCode` throws a `NullPointerException`.

   returns

     a hash value consistent with ==

   Definition Classes
     AnyRef → Any

3. #### def +(other: String): String

   Implicit information
     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 information
     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

   The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   returns

     `true` if the receiver object is equivalent to the argument; `false` otherwise.

   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

   Cast the receiver object to be of type `T0`.

   Cast the receiver object to be of type `T0`.

   Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression `1.asInstanceOf[String]` will throw a `ClassCastException` at runtime, while the expression `List(1).asInstanceOf[List[String]]` will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

   returns

     the receiver object.

   Definition Classes
     Any
   Exceptions thrown

     `ClassCastException` if the receiver object is not an instance of the erasure of type `T0`.

9. #### def bufferErrors: Boolean

10. #### def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the `clone` method is platform dependent.

    returns

      a copy of the receiver object.

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
    Note

      not specified by SLS as a member of AnyRef

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): 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 information
      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 information
      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 information
      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 information
      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

    Tests whether the argument (`that`) is a reference to the receiver object (`this`).

    Tests whether the argument (`that`) is a reference to the receiver object (`this`).

    The `eq` method implements an equivalence relation on non-null instances of `AnyRef`, and has three additional properties:

    - It is consistent: for any non-null instances `x` and `y` of type `AnyRef`, multiple invocations of `x.eq(y)` consistently returns `true` or consistently returns `false`.
    - For any non-null instance `x` of type `AnyRef`, `x.eq(null)` and `null.eq(x)` returns `false`.
    - `null.eq(null)` returns `true`.

    When overriding the `equals` or `hashCode` methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (`o1 eq o2`), they should be equal to each other (`o1 == o2`) and they should hash to the same value (`o1.hashCode == o2.hashCode`).

    returns

      `true` if the argument is a reference to the receiver object; `false` otherwise.

    Definition Classes
      AnyRef

33. #### def equals(arg0: Any): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to `eq`.

    See also `equals` in scala.Any.

    returns

      `true` if the receiver object is equivalent to the argument; `false` otherwise.

    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

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the `finalize` method is invoked, as well as the interaction between `finalize` and non-local returns and exceptions, are all platform dependent.

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )
    Note

      not specified by SLS as a member of AnyRef

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 information
      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[_]

    A representation that corresponds to the dynamic class of the receiver object.

    A representation that corresponds to the dynamic class of the receiver object.

    The nature of the representation is platform dependent.

    returns

      a representation that corresponds to the dynamic class of the receiver object.

    Definition Classes
      AnyRef → Any
    Note

      not specified by SLS as a member of AnyRef

42. #### def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

      the hash code value for this object.

    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

    Is `sym` defined in package object of package `pkg`? Since sym may be defined in some parent of the package object, we cannot inspect its owner only; we have to go through the info of the package object.

    Is `sym` defined in package object of package `pkg`? Since sym may be defined in some parent of the package object, we cannot inspect its owner only; we have to go through the info of the package object. However to avoid cycles we'll check what other ways we can before pushing that way.

63. #### final def isInstanceOf[T0]: Boolean

    Test whether the dynamic type of the receiver object is `T0`.

    Test whether the dynamic type of the receiver object is `T0`.

    Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression `1.isInstanceOf[String]` will return `false`, while the expression `List(1).isInstanceOf[List[String]]` will return `true`. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

    returns

      `true` if the receiver object is an instance of erasure of type `T0`; `false` otherwise.

    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. #### 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.

68. #### def macrosEnabled: Boolean

69. #### def macrosEnabled_=(value: Boolean): Unit

70. #### def make(tree: Global.Tree, owner: Global.Symbol, scope: Global.Scope): Analyzer.Context

71. #### 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 avaiable at the head of `Context#imports`.

72. #### 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.

73. #### 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.

74. #### 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

75. #### def makeNonSilent(newtree: Global.Tree): Analyzer.Context

76. #### 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.

77. #### var namedApplyBlockInfo: Option[(Global.Tree, Analyzer.NamedApplyInfo)]

78. #### final def ne(arg0: AnyRef): Boolean

    Equivalent to `!(this eq that)`.

    Equivalent to `!(this eq that)`.

    returns

      `true` if the argument is not a reference to the receiver object; `false` otherwise.

    Definition Classes
      AnyRef

79. #### def nextEnclosing(p: (Analyzer.Context) ⇒ Boolean): Analyzer.Context

80. #### final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
      AnyRef
    Note

      not specified by SLS as a member of AnyRef

81. #### final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
      AnyRef
    Note

      not specified by SLS as a member of AnyRef

82. #### var openImplicits: List[Analyzer.OpenImplicit]

    Types for which implicit arguments are currently searched

83. #### final def outer: Analyzer.Context

84. #### def outerDepth: Int

    Attributes
      protected

85. #### val owner: Global.Symbol

    The current owner

86. #### var prefix: Global.Type

87. #### def pushTypeBounds(sym: Global.Symbol): Unit

88. #### def reportErrors: Boolean

89. #### def reporter: Analyzer.ContextReporter

90. #### def resetCache(): Unit

91. #### def restoreTypeBounds(tp: Global.Type): Global.Type

92. #### def returnsSeen: Boolean

93. #### def returnsSeen_=(value: Boolean): Unit

94. #### def retyping: Boolean

95. #### def retyping_=(value: Boolean): Unit

96. #### var savedTypeBounds: List[(Global.Symbol, Global.Type)]

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

97. #### 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`?

98. #### val scope: Global.Scope

    The current scope

99. #### 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.

100. #### def siteString: String

101. #### def starPatterns: Boolean

102. #### def starPatterns_=(value: Boolean): Unit

103. #### final def synchronized[T0](arg0: ⇒ T0): T0

     Definition Classes
       AnyRef

104. #### def toString(): String

     Creates a String representation of this object.

     Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

     returns

       a String representation of the object.

     Definition Classes
       Context → AnyRef → Any

105. #### val tree: Global.Tree

     Tree associated with this context

106. #### def undetparams: List[Global.Symbol]

     Undetermined type parameters.

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

107. #### def undetparamsString: String

108. #### def undetparams_=(ps: List[Global.Symbol]): Unit

109. #### val unit: Global.CompilationUnit

110. #### def update(mask: ContextMode, value: Boolean): Unit

     Update all modes in `mask` to `value`

111. #### var variance: Variance

     Variance relative to enclosing class

112. #### final def wait(): Unit

     Definition Classes
       AnyRef
     Annotations
       @throws( ... )

113. #### final def wait(arg0: Long, arg1: Int): Unit

     Definition Classes
       AnyRef
     Annotations
       @throws( ... )

114. #### final def wait(arg0: Long): Unit

     Definition Classes
       AnyRef
     Annotations
       @throws( ... )

115. #### def warning(pos: Global.Position, msg: String): Unit

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

116. #### final def withImplicitsDisabled[T](op: ⇒ T): T

     Annotations
       @inline()

117. #### final def withImplicitsDisabledAllowEnrichment[T](op: ⇒ T): T

     Annotations
       @inline()

118. #### final def withImplicitsEnabled[T](op: ⇒ T): T

     Annotations
       @inline()

119. #### final def withMacrosDisabled[T](op: ⇒ T): T

     Annotations
       @inline()

120. #### final def withMacrosEnabled[T](op: ⇒ T): T

     Annotations
       @inline()

121. #### final def withMode[T](enabled: ContextMode = NOmode, disabled: ContextMode = NOmode)(op: ⇒ T): T

     Annotations
       @inline()

122. #### final def withOnlyStickyModes[T](op: ⇒ T): T

     Annotations
       @inline()

123. #### final def withinPatAlternative[T](op: ⇒ T): T

     Annotations
       @inline()

124. #### final def withinReturnExpr[T](op: ⇒ T): T

     Annotations
       @inline()

125. #### final def withinSecondTry[T](op: ⇒ T): T

     Annotations
       @inline()

126. #### final def withinStarPatterns[T](op: ⇒ T): T

     Annotations
       @inline()

127. #### final def withinSuperInit[T](op: ⇒ T): T

     Annotations
       @inline()

128. #### 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()

129. #### def →[B](y: B): (Analyzer.Context, B)

     Implicit information
       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