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 pararameters 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 defintions (`implicitss`) Supporting these are `imports`, which represents all `Import` trees in in the enclosing context chain.
- In a similar vein, we can assess accessiblity (`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`.

Intially, 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 exploraratory typing, such as determining whether `a == b` in an argument position is an assignment or a named argument, when `Infererencer#isApplicableSafe` type checks applications with and without an expected type, or whtn `Typer#tryTypedApply` tries to fit arguments to a function type with/without implicit views.

When the error policies entails 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 an separate, fresh buffer.

Source
  Contexts.scala

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ImportContext, NoContext
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2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

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### 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 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

   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 checking: Boolean

11. #### def checking_=(value: Boolean): Unit

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

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

13. #### 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

14. #### def defaultModeForTyped: Mode

15. #### def deprecationWarning(pos: Global.Position, sym: Global.Symbol): Unit

16. #### def deprecationWarning(pos: Global.Position, sym: Global.Symbol, msg: String): Unit

17. #### val depth: Int

18. #### var diagnostic: List[String]

    These messages are printed when issuing an error

19. #### def echo(pos: Global.Position, msg: String): Unit

20. #### var enclClass: Analyzer.Context

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

21. #### def enclClassOrMethod: Analyzer.Context

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

22. #### var enclMethod: Analyzer.Context

    The next outer context whose tree is a method

23. #### def enclosingApply: Analyzer.Context

    ...or an Apply.

24. #### def enclosingCaseDef: Analyzer.Context

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

25. #### def enclosingContextChain: List[Analyzer.Context]

26. #### def enclosingNonImportContext: Analyzer.Context

27. #### 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.

28. #### def enrichmentEnabled: Boolean

29. #### def enrichmentEnabled_=(value: Boolean): Unit

30. #### 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

31. #### 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

32. #### 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

33. #### 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

34. #### final def eq(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

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

    Definition Classes
      AnyRef → Any

36. #### def error(pos: Global.Position, msg: String): Unit

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

37. #### def error(pos: Global.Position, err: Throwable): Unit

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

38. #### def errors: Seq[Analyzer.AbsTypeError]

39. #### def extractUndetparams(): List[Global.Symbol]

    Return and clear the undetermined type parameters

40. #### def featureWarning(pos: Global.Position, featureName: String, featureDesc: String, featureTrait: Global.Symbol, construct: ⇒ String = "", required: Boolean): Unit

41. #### def finalize(): Unit

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

42. #### def firstError: Option[Analyzer.AbsTypeError]

    The first error, if any, in the report buffer

43. #### def firstImport: Option[Analyzer.ImportInfo]

    Equivalent to `imports.headOption`, but more efficient

44. #### def flushAndIssueWarnings(): Unit

    Issue and clear all warnings from the report buffer

45. #### def flushAndReturnBuffer(): collection.immutable.Seq[Analyzer.AbsTypeError]

    Return and clear all errors from the report buffer

46. #### def flushBuffer(): Unit

    Clear all errors from the report buffer

47. #### 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()

48. #### final def getClass(): Class[_]

    Definition Classes
      AnyRef → Any

49. #### def hasErrors: Boolean

    Does the report buffer contain any errors?

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

    Definition Classes
      AnyRef → Any

51. #### def implicitsEnabled: Boolean

52. #### def implicitsEnabled_=(value: Boolean): Unit

53. #### def implicitss: List[List[Analyzer.ImplicitInfo]]

54. #### def importedAccessibleSymbol(imp: Analyzer.ImportInfo, name: Global.Name): Global.Symbol

    The symbol with name `name` imported via the import in `imp`, if any such symbol is accessible from this context.

55. #### def imports: List[Analyzer.ImportInfo]

    The currently visible imports

56. #### def inConstructorSuffix: Boolean

57. #### def inConstructorSuffix_=(value: Boolean): Unit

58. #### def inPatAlternative: Boolean

59. #### def inPatAlternative_=(value: Boolean): Unit

60. #### def inReturnExpr: Boolean

61. #### def inSecondTry: Boolean

62. #### def inSecondTry_=(value: Boolean): Unit

63. #### def inSelfSuperCall: Boolean

64. #### def inSelfSuperCall_=(value: Boolean): Unit

65. #### final def inSilentMode(expr: ⇒ Boolean): Boolean

    returns

      true if the `expr` evaluates to true within a silent Context that incurs no errors

    Annotations
      @inline()

66. #### def inSuperInit: Boolean

67. #### def inSuperInit_=(value: Boolean): Unit

68. #### def inTypeConstructorAllowed: Boolean

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

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

70. #### 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.

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

    Definition Classes
      Any

72. #### def isNameInScope(name: Global.Name): Boolean

73. #### def isRootImport: Boolean

74. #### def issue(err: Analyzer.AbsTypeError): Unit

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

75. #### def issueAmbiguousError(err: Analyzer.AbsTypeError): Unit

    Issue/buffer/throw the given implicit ambiguity error according to the current mode for error reporting.

76. #### def issueAmbiguousError(pre: Global.Type, sym1: Global.Symbol, sym2: Global.Symbol, err: Analyzer.AbsTypeError): Unit

    Issue/buffer/throw the given implicit ambiguity error according to the current mode for error reporting.

77. #### 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

78. #### 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.

79. #### def macrosEnabled: Boolean

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

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

82. #### def make(tree: Global.Tree = tree, owner: Global.Symbol = owner, scope: Global.Scope = scope, unit: Global.CompilationUnit = unit): 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`.

83. #### 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.

84. #### 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.

85. #### def makeNewScope(tree: Global.Tree, owner: Global.Symbol): Analyzer.Context

    Make a child context that represents a new nested scope

86. #### 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.

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

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

    Definition Classes
      AnyRef

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

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

    Definition Classes
      AnyRef

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

    Definition Classes
      AnyRef

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

    Types for which implicit arguments are currently searched

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

94. #### def outerDepth: Int

    Attributes
      protected

95. #### val owner: Global.Symbol

    The current owner

96. #### var prefix: Global.Type

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

98. #### def reportBuffer: Analyzer.ReportBuffer

    A buffer for errors and warnings, used with `this.bufferErrors == true`

99. #### def reportErrors: Boolean

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

101. #### def restoreReportBuffer(other: Analyzer.ReportBuffer): Unit

     Discard the current report buffer, and replace with `other`

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

103. #### def returnsSeen: Boolean

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

105. #### def retyping: Boolean

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

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

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

108. #### 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`?

109. #### val scope: Global.Scope

     The current scope

110. #### 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.

111. #### def setAmbiguousErrors(report: Boolean): Unit

112. #### def setBufferErrors(): Unit

113. #### def setReportErrors(): Unit

114. #### def setThrowErrors(): Unit

115. #### def siteString: String

116. #### def starPatterns: Boolean

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

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

     Definition Classes
       AnyRef

119. #### def throwErrors: Boolean

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

     Definition Classes
       Context → AnyRef → Any

121. #### val tree: Global.Tree

     Tree associated with this context

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

     Undetermined type parameters.

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

123. #### def undetparamsString: String

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

125. #### val unit: Global.CompilationUnit

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

     Update all modes in `mask` to `value`

127. #### def updateBuffer(errors: Traversable[Analyzer.AbsTypeError]): Analyzer.ReportBuffer

     Append the given errors to the report buffer

128. #### def useFreshReportBuffer(): Unit

     Discard the current report buffer, and replace with an empty one

129. #### var variance: Variance

     Variance relative to enclosing class

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

     Definition Classes
       AnyRef
     Annotations
       @throws( ... )

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

     Definition Classes
       AnyRef
     Annotations
       @throws( ... )

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

     Definition Classes
       AnyRef
     Annotations
       @throws( ... )

133. #### def warning(pos: Global.Position, msg: String, force: Boolean = false): Unit

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

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

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

     Annotations
       @inline()

146. #### 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()

147. #### 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