Packages

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
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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. def ambiguousErrors: Boolean
  2. def apply(mask: ContextMode): Boolean

    Is this context in all modes in the given mask?

  3. def bufferErrors: Boolean
  4. 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

  5. def defaultModeForTyped: Mode
  6. def deprecationWarning(pos: Global.Position, sym: Global.Symbol): Unit
  7. def deprecationWarning(pos: Global.Position, sym: Global.Symbol, msg: String, since: String): Unit
  8. val depth: Int
  9. 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.

  10. def echo(pos: Global.Position, msg: String): Unit
  11. var enclClass: Analyzer.Context

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

  12. def enclClassOrMethod: Analyzer.Context

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

  13. var enclMethod: Analyzer.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).

  14. def enclosingApply: Analyzer.Context

    ...or an Apply.

  15. def enclosingCaseDef: Analyzer.Context

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

  16. def enclosingContextChain: List[Analyzer.Context]
  17. final def enclosingImport: Analyzer.Context
    Annotations
    @tailrec()
  18. def enclosingNonImportContext: Analyzer.Context
  19. 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.

  20. def enrichmentEnabled: Boolean
  21. def enrichmentEnabled_=(value: Boolean): Unit
  22. def error(pos: Global.Position, msg: String): Unit

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

  23. def extractUndetparams(): List[Global.Symbol]

    Return and clear the undetermined type parameters

  24. def featureWarning(pos: Global.Position, featureName: String, featureDesc: String, featureTrait: Global.Symbol, construct: ⇒ String = "", required: Boolean): Unit
  25. def firstImport: Option[Analyzer.ImportInfo]

    Equivalent to imports.headOption, but more efficient

  26. def fixPosition(pos: Global.Position): Global.Position
  27. def implicitsEnabled: Boolean
  28. def implicitsEnabled_=(value: Boolean): Unit
  29. def implicitss: List[List[Analyzer.ImplicitInfo]]
  30. def imports: List[Analyzer.ImportInfo]

    The currently visible imports, from innermost to outermost.

  31. def inConstructorSuffix: Boolean
  32. def inConstructorSuffix_=(value: Boolean): Unit
  33. def inPatAlternative: Boolean
  34. def inPatAlternative_=(value: Boolean): Unit
  35. def inReturnExpr: Boolean
  36. def inSecondTry: Boolean
  37. def inSecondTry_=(value: Boolean): Unit
  38. def inSelfSuperCall: Boolean
  39. def inSelfSuperCall_=(value: Boolean): Unit
  40. final def inSilentMode(expr: ⇒ Boolean): Boolean
    Annotations
    @inline()
  41. def inSuperInit: Boolean
  42. def inSuperInit_=(value: Boolean): Unit
  43. def inTypeConstructorAllowed: Boolean
  44. def initRootContext(throwing: Boolean = false, checking: Boolean = false): Unit

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

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

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

  46. 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?

  47. def isNameInScope(name: Global.Name): Boolean
  48. 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)

  49. final def isSearchingForImplicitParam: Boolean
  50. final def javaFindMember(pre: Global.Type, name: Global.Name, qualifies: (Global.Symbol) ⇒ Boolean): (Global.Type, Global.Symbol)
  51. final def lookupCompanionInIncompleteOwner(original: Global.Symbol): Global.Symbol
  52. final def lookupSibling(original: Global.Symbol, name: Global.Name): Global.Symbol
  53. def lookupSymbol(name: Global.Name, qualifies: (Global.Symbol) ⇒ Boolean): Global.NameLookup
  54. def macrosEnabled: Boolean
  55. def macrosEnabled_=(value: Boolean): Unit
  56. def make(tree: Global.Tree, owner: Global.Symbol, scope: Global.Scope): Analyzer.Context
  57. 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.

  58. 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.

  59. 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.

  60. 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

  61. def makeNonSilent(newtree: Global.Tree): Analyzer.Context
  62. 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.

  63. def nextEnclosing(p: (Analyzer.Context) ⇒ Boolean): Analyzer.Context
  64. var openImplicits: List[Analyzer.OpenImplicit]

    Types for which implicit arguments are currently searched

  65. final def outer: Analyzer.Context
  66. final def outermostContextAtCurrentPos: Analyzer.Context
  67. val owner: Global.Symbol
  68. var prefix: Global.Type
  69. def pushTypeBounds(sym: Global.Symbol): Unit
  70. def reportErrors: Boolean
  71. def reporter: Analyzer.ContextReporter
  72. def resetCache(): Unit
  73. def restoreTypeBounds(tp: Global.Type): Global.Type
  74. def returnsSeen: Boolean
  75. def returnsSeen_=(value: Boolean): Unit
  76. def retyping: Boolean
  77. def retyping_=(value: Boolean): Unit
  78. var savedTypeBounds: List[(Global.Symbol, Global.Type)]

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

  79. 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?

  80. val scope: Global.Scope
  81. 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.

  82. def siteString: String
  83. def starPatterns: Boolean
  84. def starPatterns_=(value: Boolean): Unit
  85. def toString(): String
    Definition Classes
    Context → AnyRef → Any
  86. val tree: Global.Tree
  87. def undetparams: List[Global.Symbol]

    Undetermined type parameters.

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

  88. def undetparamsString: String
  89. def undetparams_=(ps: List[Global.Symbol]): Unit
  90. val unit: Global.CompilationUnit
  91. def update(mask: ContextMode, value: Boolean): Unit

    Update all modes in mask to value

  92. var variance: Variance

    Variance relative to enclosing class

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

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

  94. final def withImplicits[T](enabled: Boolean)(op: ⇒ T): T
    Annotations
    @inline()
  95. final def withImplicitsDisabled[T](op: ⇒ T): T
    Annotations
    @inline()
  96. final def withImplicitsDisabledAllowEnrichment[T](op: ⇒ T): T
    Annotations
    @inline()
  97. final def withImplicitsEnabled[T](op: ⇒ T): T
    Annotations
    @inline()
  98. final def withMacros[T](enabled: Boolean)(op: ⇒ T): T
    Annotations
    @inline()
  99. final def withMacrosDisabled[T](op: ⇒ T): T
    Annotations
    @inline()
  100. final def withMacrosEnabled[T](op: ⇒ T): T
    Annotations
    @inline()
  101. final def withMode[T](enabled: ContextMode = NOmode, disabled: ContextMode = NOmode)(op: ⇒ T): T
    Annotations
    @inline()
  102. final def withOnlyStickyModes[T](op: ⇒ T): T
    Annotations
    @inline()
  103. final def withSuppressDeadArgWarning[T](suppress: Boolean)(op: ⇒ T): T
    Annotations
    @inline()
  104. final def withinPatAlternative[T](op: ⇒ T): T
    Annotations
    @inline()
  105. final def withinReturnExpr[T](op: ⇒ T): T
    Annotations
    @inline()
  106. final def withinSecondTry[T](op: ⇒ T): T
    Annotations
    @inline()
  107. final def withinStarPatterns[T](op: ⇒ T): T
    Annotations
    @inline()
  108. final def withinSuperInit[T](op: ⇒ T): T
    Annotations
    @inline()
  109. 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()