Disallow phase inconsistent inline parameters #8061
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nicolasstucki
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Will need to be rebased on #8077 (the second commit will disapear) |
| inline def power(x: Double, inline n: Int) = ${ powerCode('x, 'n) } | ||
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| private def powerCode(x: Expr[Double], n: Expr[Int]): Expr[Double] = | ||
| powerCode(x, n.value) // Transform `n` into an Int or emit an error if it is not possible |
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Maybe do it safely by n.getValue
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This has the same semantics as before. If the inline parameter is not a constant, an error is emitted.
| def unapply[T](expr: Expr[T])(given valueOf: ValueOfExpr[T], qxtc: QuoteContext): Option[T] = | ||
| valueOf(expr) | ||
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| } |
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We already have extractor for Const, a duplicate? The name Value is a little misleading, if we in fact only want to get the literal const out.
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Yes, Value is more general. I plan to replace and remove Const in another PR
| * Otherwise returns the value. | ||
| */ | ||
| final def value[U >: T](given qctx: QuoteContext, valueOf: ValueOfExpr[U]): U = | ||
| valueOf(this).getOrElse(qctx.throwError(s"Expected a known value. \n\nThe value of: $show\ncould not be recovered using $valueOf", this)) |
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It seems this method only invites errors in meta-programming, maybe we should just remove it.
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Without it we would end up writing expr.getValue.get all over the place which would crash the macro expansion. This alternative emits an error saying that the call expected a constant value. Pointing to the argument that is not a value.
| @@ -18,6 +18,14 @@ class Expr[+T] private[scala] { | |||
| */ | |||
| final def getValue[U >: T](given qctx: QuoteContext, valueOf: ValueOfExpr[U]): Option[U] = valueOf(this) | |||
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I find getValue is a little misleading, if what it does is to get the literal out. Maybe getLiteralValue?
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It is not necessarily a literal value.
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In preparation for #8060.
Originally we used
inlineparameters as the way to recover statically known values from the arguments. This worked on some predefined types such as literal primitives, case objects, case classes, enums among others. The latter ones where ad-hoc addons without a clear specification.ValueOfExpralso recovers statically known values but it is more general. It can be implemented for any arbitrary type that represents a value. In this PR we introduce some extra ways to use this such asExpr.value,matching.Valueandmatching.ValueSeq.ValueOfExprmakes the current use of inline parameters completely redundant hence this PR replaces all uses of inline parameters by equivalent code usingValueOfExpr.It also simplifies the PCP as it removes a special case from the rules.