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:
outer
.contextMode
.And behaviour:
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.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.
A reporter for use during type checking.
A reporter for use during type checking. It has multiple modes for handling errors.
The default (immediate mode) is to send the error to the global reporter. When switched into buffering mode via makeBuffering, errors and warnings are buffered and not be reported (there's a special case for ambiguity errors for some reason: those are force to the reporter when context.ambiguousErrors, or else they are buffered -- TODO: can we simplify this?)
When using the type checker after typers, an error results in a TypeError being thrown. TODO: get rid of this mode.
To handle nested contexts, reporters share buffers. TODO: only buffer in BufferingReporter, emit immediately in ImmediateReporter
A Context
focussed on an Import
tree
Test two objects for inequality.
Test two objects for inequality.
true
if !(this == that), false otherwise.
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
.
a hash value consistent with ==
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)
.
true
if the receiver object is equivalent to the argument; false
otherwise.
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.
the receiver object.
ClassCastException
if the receiver object is not an instance of the erasure of type T0
.
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the clone
method is platform dependent.
a copy of the receiver object.
not specified by SLS as a member of AnyRef
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:
x
and y
of type AnyRef
, multiple invocations of
x.eq(y)
consistently returns true
or consistently returns false
.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
).
true
if the argument is a reference to the receiver object; false
otherwise.
The equality method for reference types.
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.
not specified by SLS as a member of AnyRef
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.
a representation that corresponds to the dynamic class of the receiver object.
not specified by SLS as a member of AnyRef
The hashCode method for reference types.
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.
true
if the receiver object is an instance of erasure of type T0
; false
otherwise.
Equivalent to !(this eq that)
.
Equivalent to !(this eq that)
.
true
if the argument is not a reference to the receiver object; false
otherwise.
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.
not specified by SLS as a member of AnyRef
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.
not specified by SLS as a member of AnyRef
List of symbols to import from in a root context.
List of symbols to import from in a root context. Typically that
is java.lang
, scala
, and scala.Predef, in that order. Exceptions:
-Yno-imports
is given, nothing is importedjava.lang
is imported-Yno-predef
is given, if the unit body has an import of Predef
among its leading imports, or if the tree is scala.Predef, Predef
is not imported.
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.
a String representation of the object.
1.0