8000 TypeTag => WeakTypeTag in the macro guide by xeno-by · Pull Request #184 · scala/docs.scala-lang · GitHub
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TypeTag => WeakTypeTag in the macro guide #184

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Feb 17, 2013
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TypeTag => WeakTypeTag in the macro guide #184

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6 changes: 3 additions & 3 deletions overviews/macros/overview.md
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Expand Up @@ -74,7 +74,7 @@ or with `-language:experimental.macros` (providing a compiler switch) on per-com

### Generic macros

Macro definitions and macro implementations may both be generic. If a macro implementation has type parameters, actual type arguments must be given explicitly in the macro definition’s body. Type parameters in an implementation may come with `TypeTag` context bounds. In that case the corresponding type tags describing the actual type arguments instantiated at the application site will be passed along when the macro is expanded.
Macro definitions and macro implementations may both be generic. If a macro implementation has type parameters, actual type arguments must be given explicitly in the macro definition’s body. Type parameters in an implementation may come with `WeakTypeTag` context bounds. In that case the corresponding type tags describing the actual type arguments instantiated at the application site will be passed along when the macro is expanded.

The following code snippet declares a macro definition `Queryable.map` that references a macro implementation `QImpl.map`:

Expand All @@ -83,7 +83,7 @@ The following code snippet declares a macro definition `Queryable.map` that refe
}

object QImpl {
def map[T: c.TypeTag, U: c.TypeTag]
def map[T: c.WeakTypeTag, U: c.WeakTypeTag]
(c: Context)
(p: c.Expr[T => U]): c.Expr[Queryable[U]] = ...
}
Expand All @@ -95,7 +95,7 @@ Now consider a value `q` of type `Queryable[String]` and a macro call
The call is expanded to the following reflective macro invocation

QImpl.map(c)(<[ s => s.length ]>)
(implicitly[TypeTag[String]], implicitly[TypeTag[Int]])
(implicitly[WeakTypeTag[String]], implicitly[WeakTypeTag[Int]])

## A complete example

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