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Align description how context bounds expand with implementation #15297

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May 27, 2022
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Align description how context bounds expand with implementation #15297

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11 changes: 9 additions & 2 deletions docs/_docs/reference/contextual/context-bounds.md
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Expand Up @@ -10,7 +10,14 @@ A context bound is a shorthand for expressing the common pattern of a context pa
def maximum[T: Ord](xs: List[T]): T = xs.reduceLeft(max)
```

A bound like `: Ord` on a type parameter `T` of a method or class indicates a context parameter `using Ord[T]`. The context parameter(s) generated from context bounds come last in the definition of the containing method or class. For instance,
A bound like `: Ord` on a type parameter `T` of a method or class indicates a context parameter `using Ord[T]`. The context parameter(s) generated from context bounds
are added as follows:

- If the method parameters end in an implicit parameter list or using clause,
context parameters are added in front of that list.
- Otherwise they are added as a separate parameter clause at the end.

Example:

```scala
def f[T: C1 : C2, U: C3](x: T)(using y: U, z: V): R
Expand All @@ -19,7 +26,7 @@ def f[T: C1 : C2, U: C3](x: T)(using y: U, z: V): R
would expand to

```scala
def f[T, U](x: T)(using y: U, z: V)(using C1[T], C2[T], C3[U]): R
def f[T, U](x: T)(using _: C1[T], _: C2[T], _: C3[U], y: U, z: V): R
```

Context bounds can be combined with subtype bounds. If both are present, subtype bounds come first, e.g.
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