Scala Compiler2.12.2-20170504-135222-21d12e9 < 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

-  class Context extends AnyRef

  A motley collection of the state and loosely associated behaviour of the type checker.

  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.

  Definition Classes
    Contexts
- TryTwice

c

scala.tools.nsc.typechecker.Contexts.Context

# TryTwice 

###

#### abstract class TryTwice extends AnyRef

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

Source
  Contexts.scala

Linear Supertypes
AnyRef, Any
Type Hierarchy
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Ordering

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2. By Inheritance

Inherited

1. TryTwice
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

### Instance Constructors

1.  new TryTwice()

### Abstract Value Members

1.  abstract def tryOnce(isLastTry: Boolean): Unit

### Concrete 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 TryTwice to any2stringadd[TryTwice] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (TryTwice, B)
   Implicit
     This member is added by an implicit conversion from TryTwice to ArrowAssoc[TryTwice] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()
5.  final def ==(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
6.  final def apply(): Unit
7.  final def asInstanceOf[T0]: T0
   Definition Classes
     Any
8.  def clone(): AnyRef
   Attributes
     protected[java.lang]
   Definition Classes
     AnyRef
   Annotations
     @throws( ... )
9.  def ensuring(cond: (TryTwice) ⇒ Boolean, msg: ⇒ Any): TryTwice
   Implicit
     This member is added by an implicit conversion from TryTwice to Ensuring[TryTwice] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
10.  def ensuring(cond: (TryTwice) ⇒ Boolean): TryTwice
    Implicit
      This member is added by an implicit conversion from TryTwice to Ensuring[TryTwice] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
11.  def ensuring(cond: Boolean, msg: ⇒ Any): TryTwice
    Implicit
      This member is added by an implicit conversion from TryTwice to Ensuring[TryTwice] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
12.  def ensuring(cond: Boolean): TryTwice
    Implicit
      This member is added by an implicit conversion from TryTwice to Ensuring[TryTwice] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
13.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
14.  def equals(arg0: Any): Boolean
    Definition Classes
      AnyRef → Any
15.  def finalize(): Unit
    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )
16.  def formatted(fmtstr: String): String
    Implicit
      This member is added by an implicit conversion from TryTwice to StringFormat[TryTwice] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()
17.  final def getClass(): Class[_]
    Definition Classes
      AnyRef → Any
18.  def hashCode(): Int
    Definition Classes
      AnyRef → Any
19.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
20.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
21.  final def notify(): Unit
    Definition Classes
      AnyRef
22.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
23.  final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
      AnyRef
24.  def toString(): String
    Definition Classes
      AnyRef → Any
25.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
26.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
27.  final def wait(arg0: Long): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
28.  def →[B](y: B): (TryTwice, B)
    Implicit
      This member is added by an implicit conversion from TryTwice to ArrowAssoc[TryTwice] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from TryTwice to any2stringadd[TryTwice]

### Inherited by implicit conversion StringFormat from TryTwice to StringFormat[TryTwice]

### Inherited by implicit conversion Ensuring from TryTwice to Ensuring[TryTwice]

### Inherited by implicit conversion ArrowAssoc from TryTwice to ArrowAssoc[TryTwice]

### Ungrouped