Skip to content

SI-7161 Remove Manifests from spec #119

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 1 commit into from
Closed

SI-7161 Remove Manifests from spec #119

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
93 changes: 0 additions & 93 deletions documentation/src/reference/ReferencePart.tex
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6120,86 +6120,6 @@ \section{Context Bounds and View Bounds}\label{sec:context-bounds}
def <= [B >: A <% Ordered[B]](that: B): Boolean
\end{lstlisting}

\section{Manifests}\label{sec:manifests}

\newcommand{\Mobj}{\mbox{\sl Mobj}}

Manifests are type descriptors that can be automatically generated by
the Scala compiler as arguments to implicit parameters. The Scala
standard library contains a hierarchy of four manifest classes,
with \lstinline@OptManifest@
at the top. Their signatures follow the outline below.
\begin{lstlisting}
trait OptManifest[+T]
object NoManifest extends OptManifest[Nothing]
trait ClassManifest[T] extends OptManifest[T]
trait Manifest[T] extends ClassManifest[T]
\end{lstlisting}

If an implicit parameter of a method or constructor is of a subtype $M[T]$ of
class \lstinline@OptManifest[T]@, {\em a manifest is determined for $M[S]$},
according to the following rules.

First if there is already an implicit argument that matches $M[T]$, this
argument is selected.

Otherwise, let $\Mobj$ be the companion object \[email protected]@
if $M$ is trait \lstinline@Manifest@, or be
the companion object \[email protected]@ otherwise. Let $M'$ be the trait
\lstinline@Manifest@ if $M$ is trait \lstinline@Manifest@, or be the trait \lstinline@OptManifest@ otherwise.
Then the following rules apply.


\begin{enumerate}
\item
If $T$ is a value class or one of the classes \lstinline@Any@, \lstinline@AnyVal@, \lstinline@Object@,
\lstinline@Null@, or \lstinline@Nothing@,
a manifest for it is generated by selecting
the corresponding manifest value \lstinline@Manifest.$T$@, which exists in the
\lstinline@Manifest@ module.
\item
If $T$ is an instance of \lstinline@Array[$S$]@, a manifest is generated
with the invocation \lstinline@$\Mobj$.arrayType[S](m)@, where $m$ is the manifest
determined for $M[S]$.
\item
If $T$ is some other class type $S\#C[U_1 \commadots U_n]$ where the prefix type $S$
cannot be statically determined from the class $C$,
a manifest is generated
with the invocation \lstinline@$\Mobj$.classType[T]($m_0$, classOf[T], $ms$)@
where $m_0$ is the manifest determined for $M'[S]$ and $ms$ are the
manifests determined for $M'[U_1] \commadots M'[U_n]$.
\item
If $T$ is some other class type with type arguments $U_1 \commadots U_n$,
a manifest is generated
with the invocation \lstinline@$\Mobj$.classType[T](classOf[T], $ms$)@
where $ms$ are the
manifests determined for $M'[U_1] \commadots M'[U_n]$.
\item
If $T$ is a singleton type ~\lstinline@$p$.type@, a manifest is generated with
the invocation
\lstinline@$\Mobj$.singleType[T]($p$)@
\item
If $T$ is a refined type $T' \{ R \}$, a manifest is generated for $T'$.
(That is, refinements are never reflected in manifests).
\item
If $T$ is an intersection type
\lstinline@$T_1$ with $\commadots$ with $T_n$@
where $n > 1$, the result depends on whether a full manifest is
to be determined or not.
If $M$ is trait \lstinline@Manifest@, then
a manifest is generated with the invocation
\[email protected][T]($ms$)@ where $ms$ are the manifests
determined for $M[T_1] \commadots M[T_n]$.
Otherwise, if $M$ is trait \lstinline@ClassManifest@,
then a manifest is generated for the intersection dominator
(\sref{sec:erasure})
of the types $T_1 \commadots T_n$.
\item
If $T$ is some other type, then if $M$ is trait \lstinline@OptManifest@,
a manifest is generated from the designator \[email protected]@.
If $M$ is a type different from \lstinline@OptManifest@, a static error results.
\end{enumerate}

\chapter{Pattern Matching}

\section{Patterns}
Expand Down Expand Up @@ -8204,19 +8124,6 @@ \section{The \large{\code{Predef}} Object}\label{cls:predef}
val Map = collection.immutable.Map
val Set = collection.immutable.Set

// Manifest types, companions, and incantations for summoning ---------

type ClassManifest[T] = scala.reflect.ClassManifest[T]
type Manifest[T] = scala.reflect.Manifest[T]
type OptManifest[T] = scala.reflect.OptManifest[T]
val ClassManifest = scala.reflect.ClassManifest
val Manifest = scala.reflect.Manifest
val NoManifest = scala.reflect.NoManifest

def manifest[T](implicit m: Manifest[T]) = m
def classManifest[T](implicit m: ClassManifest[T]) = m
def optManifest[T](implicit m: OptManifest[T]) = m

// Minor variations on identity functions -----------------------------
def identity[A](x: A): A = x // @see `conforms` for the implicit version
def implicitly[T](implicit e: T) = e // for summoning implicit values from the nether world
Expand Down