Disallow inline given aliases with functions as RHS #16498
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```scala
inline given a: Conversion[String, Item] = Item(_) // error
```
will now produce this error:
```
5 | inline given a: Conversion[String, Item] = Item(_) // error
| ^^^^^^^
|inline given alias cannot have a function value as right-hand side.
|Either drop `inline` or rewrite the given with an explicit `apply` method.
|-----------------------------------------------------------------------------
| Explanation (enabled by `-explain`)
|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| A function value on the right-hand side of an inline given alias would expand to
| an anonymous class. Each application of the inline given would then create a
| fresh copy of that class, which can increase code size in surprising ways.
| For that reason, functions are disallowed as right hand sides of inline given aliases.
| You should either drop `inline` or rewrite to an explicit `apply` method. E.g.
|
| inline given Conversion[A, B] = x => x.toB // error
|
| should be re-formulated as
|
| inline given Conversion[A, B] with
| def apply(x: A) = x.toB
|
```
Fixes scala#16497
|
I am going to close this in favor of #16499 |
odersky
added a commit
that referenced
this pull request
Dec 15, 2022
```scala
inline given a: Conversion[String, Item] = Item(_)
```
will now produce this warning:
```
5 | inline given a: Conversion[String, Item] = Item(_)
| ^^^^^^^
|An inline given alias with a function value as right-hand side can significantly increase
|generated code size. You should either drop the `inline` or rewrite the given with an
|explicit `apply` method.
|----------------------------------------------------------------------------
| Explanation (enabled by `-explain`)
|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| A function value on the right-hand side of an inline given alias expands to
| an anonymous class. Each application of the inline given will then create a
| fresh copy of that class, which can increase code size in surprising ways.
| For that reason, functions are discouraged as right hand sides of inline given aliases.
| You should either drop `inline` or rewrite to an explicit `apply` method. E.g.
|
| inline given Conversion[A, B] = x => x.toB
|
| should be re-formulated as
|
| inline given Conversion[A, B] with
| def apply(x: A) = x.toB
|
```
Fixes #16497
Alternative to #16498
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will now produce this error:
Fixes #16497
Alternative to #16499