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Merge pull request #6819 from dotty-staging/quote-implicit-search
Allow to search for implicits in macros
2 parents 7c33774 + 041647c commit 863872b

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‎compiler/src/dotty/tools/dotc/tastyreflect/KernelImpl.scala

Lines changed: 44 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,7 @@ package tastyreflect
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import dotty.tools.dotc.ast.Trees.SeqLiteral
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import dotty.tools.dotc.ast.{Trees, tpd, untpd}
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import dotty.tools.dotc.ast.tpd.TreeOps
7-
import dotty.tools.dotc.typer.Typer
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import dotty.tools.dotc.typer.{Implicits, Typer}
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import dotty.tools.dotc.core._
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import dotty.tools.dotc.core.Flags._
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import dotty.tools.dotc.core.StdNames.nme
@@ -13,6 +13,7 @@ import dotty.tools.dotc.core.Symbols._
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import dotty.tools.dotc.core.Decorators._
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import dotty.tools.dotc.tastyreflect.FromSymbol.{definitionFromSym, packageDefFromSym}
1515
import dotty.tools.dotc.parsing.Parsers.Parser
16+
import dotty.tools.dotc.typer.Implicits.{AmbiguousImplicits, DivergingImplicit, NoMatchingImplicits, SearchFailure, SearchFailureType}
1617
import dotty.tools.dotc.util.SourceFile
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import scala.tasty.reflect.Kernel
@@ -1849,6 +1850,48 @@ class KernelImpl(val rootContext: core.Contexts.Context, val rootPosition: util.
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def Definitions_NullType: Type = defn.NullType
18501851
def Definitions_StringType: Type = defn.StringType
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//
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// IMPLICITS
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//
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type ImplicitSearchResult = Tree
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def searchImplicit(tpe: Type)(implicit ctx: Context): ImplicitSearchResult =
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ctx.typer.inferImplicitArg(tpe, rootPosition.span)
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type ImplicitSearchSuccess = Tree
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def matchImplicitSearchSuccess(isr: ImplicitSearchResult)(implicit ctx: Context): Option[ImplicitSearchSuccess] = isr.tpe match {
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case _: SearchFailureType => None
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case _ => Some(isr)
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}
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def ImplicitSearchSuccess_tree(self: ImplicitSearchSuccess)(implicit ctx: Context): Term = self
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type ImplicitSearchFailure = Tree
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def matchImplicitSearchFailure(isr: ImplicitSearchResult)(implicit ctx: Context): Option[ImplicitSearchFailure] = isr.tpe match {
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case _: SearchFailureType => Some(isr)
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case _ => None
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}
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def ImplicitSearchFailure_explanation(self: ImplicitSearchFailure)(implicit ctx: Context): String =
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self.tpe.asInstanceOf[SearchFailureType].explanation
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type DivergingImplicit = Tree
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def matchDivergingImplicit(isr: ImplicitSearchResult)(implicit ctx: Context): Option[DivergingImplicit] = isr.tpe match {
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case _: Implicits.DivergingImplicit => Some(isr)
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case _ => None
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}
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type NoMatchingImplicits = Tree
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def matchNoMatchingImplicits(isr: ImplicitSearchResult)(implicit ctx: Context): Option[NoMatchingImplicits] = isr.tpe match {
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case _: Implicits.NoMatchingImplicits => Some(isr)
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case _ => None
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}
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type AmbiguousImplicits = Tree
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def matchAmbiguousImplicits(isr: ImplicitSearchResult)(implicit ctx: Context): Option[AmbiguousImplicits] = isr.tpe match {
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case _: Implicits.AmbiguousImplicits => Some(isr)
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case _ => None
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}
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//
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// HELPERS
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//

‎docs/docs/reference/metaprogramming/macros.md

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@@ -569,6 +569,22 @@ while (i < arr.length) {
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sum
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```
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### Find implicits within a macro
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Similarly to the `implicit match` construct, it is possible to make implicit search available
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in a quote context. For this we simply provide `scala.quoted.matching.searchImplicitExpr:
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```scala
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inline def setFor[T]: Set[T] = ${ setForExpr[T] }
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def setForExpr[T: Type] given QuoteContext: Expr[Set[T]] = {
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searchImplicitExpr[Ordering[T]] match {
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case Some(ord) => '{ new TreeSet[T]()($ord) }
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case _ => '{ new HashSet[T] }
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}
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}
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```
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572588
### Relationship with Whitebox Inline
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[Inline](./inline.md) documents inlining. The code below introduces a whitebox

‎library/src/scala/quoted/matching/package.scala

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@@ -0,0 +1,21 @@
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package scala.quoted
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package object matching {
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/** Find an implicit of type `T` in the current scope given by `qctx`.
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* Return `Some` containing the expression of the implicit or
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* `None` if implicit resolution failed.
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*
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* @tparam T type of the implicit parameter
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* @param tpe quoted type of the implicit parameter
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* @param qctx current context
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*/
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def searchImplicitExpr[T] given (tpe: Type[T], qctx: QuoteContext): Option[Expr[T]] = {
14+
import qctx.tasty._
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searchImplicit(tpe.unseal.tpe) match {
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case IsImplicitSearchSuccess(iss) => Some(iss.tree.seal.asInstanceOf[Expr[T]])
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case IsImplicitSearchFailure(isf) => None
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}
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}
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}

‎library/src/scala/tasty/Reflection.scala

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Original file line numberDiff line numberDiff line change
@@ -9,6 +9,7 @@ class Reflection(val kernel: Kernel)
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with CommentOps
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with FlagsOps
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with IdOps
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with ImplicitsOps
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with ImportSelectorOps
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with QuotedOps
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with PatternOps

‎library/src/scala/tasty/reflect/Core.scala

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@@ -456,4 +456,17 @@ trait Core {
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/** FlagSet of a Symbol */
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type Flags = kernel.Flags
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type ImplicitSearchResult = kernel.ImplicitSearchResult
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type ImplicitSearchSuccess = kernel.ImplicitSearchSuccess
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type ImplicitSearchFailure = kernel.ImplicitSearchFailure
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type DivergingImplicit = kernel.DivergingImplicit
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type NoMatchingImplicits = kernel.NoMatchingImplicits
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type AmbiguousImplicits = kernel.AmbiguousImplicits
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}

‎library/src/scala/tasty/reflect/ImplicitsOps.scala

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@@ -0,0 +1,41 @@
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package scala.tasty.reflect
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trait ImplicitsOps extends Core {
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def searchImplicit(tpe: Type)(implicit ctx: Context): ImplicitSearchResult =
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kernel.searchImplicit(tpe)
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object IsImplicitSearchSuccess {
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def unapply(isr: ImplicitSearchResult)(implicit ctx: Context): Option[ImplicitSearchSuccess] =
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kernel.matchImplicitSearchSuccess(isr)
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}
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implicit class IsImplicitSearchSuccessAPI(self: ImplicitSearchSuccess) {
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def tree(implicit ctx: Context): Term = kernel.ImplicitSearchSuccess_tree(self)
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}
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object IsImplicitSearchFailure {
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def unapply(isr: ImplicitSearchResult)(implicit ctx: Context): Option[ImplicitSearchFailure] =
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kernel.matchImplicitSearchFailure(isr)
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}
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implicit class ImplicitSearchFailureAPI(self: ImplicitSearchFailure) {
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def explanation(implicit ctx: Context): String = kernel.ImplicitSearchFailure_explanation(self)
24+
}
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object IsDivergingImplicit {
27+
def unapply(isr: ImplicitSearchResult)(implicit ctx: Context): Option[DivergingImplicit] =
28+
kernel.matchDivergingImplicit(isr)
29+
}
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object IsNoMatchingImplicits {
32+
def unapply(isr: ImplicitSearchResult)(implicit ctx: Context): Option[NoMatchingImplicits] =
33+
kernel.matchNoMatchingImplicits(isr)
34+
}
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object IsAmbiguousImplicits {
37+
def unapply(isr: ImplicitSearchResult)(implicit ctx: Context): Option[AmbiguousImplicits] =
38+
kernel.matchAmbiguousImplicits(isr)
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}
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}

‎library/src/scala/tasty/reflect/Kernel.scala

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@@ -1,5 +1,7 @@
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package scala.tasty.reflect
22

3+
import scala.quoted.QuoteContext
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35
/** Tasty reflect abstract types
46
*
57
* ```none
@@ -1506,4 +1508,35 @@ trait Kernel {
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def Definitions_NullType: Type
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def Definitions_StringType: Type
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1511+
//
1512+
// IMPLICITS
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//
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type ImplicitSearchResult <: AnyRef
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type ImplicitSearchSuccess <: ImplicitSearchResult
1518+
def matchImplicitSearchSuccess(isr: ImplicitSearchResult)(implicit ctx: Context): Option[ImplicitSearchSuccess]
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def ImplicitSearchSuccess_tree(self: ImplicitSearchSuccess)(implicit ctx: Context): Term
1520+
1521+
type ImplicitSearchFailure <: ImplicitSearchResult
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def matchImplicitSearchFailure(isr: ImplicitSearchResult)(implicit ctx: Context): Option[ImplicitSearchFailure]
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def ImplicitSearchFailure_explanation(self: ImplicitSearchFailure)(implicit ctx: Context): String
1524+
1525+
type DivergingImplicit <: ImplicitSearchFailure
1526+
def matchDivergingImplicit(isr: ImplicitSearchResult)(implicit ctx: Context): Option[DivergingImplicit]
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1528+
type NoMatchingImplicits <: ImplicitSearchFailure
1529+
def matchNoMatchingImplicits(isr: ImplicitSearchResult)(implicit ctx: Context): Option[NoMatchingImplicits]
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1531+
type AmbiguousImplicits <: ImplicitSearchFailure
1532+
def matchAmbiguousImplicits(isr: ImplicitSearchResult)(implicit ctx: Context): Option[AmbiguousImplicits]
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1534+
/** Find an implicit of type `T` in the current scope given by `ctx`.
1535+
* Return an `ImplicitSearchResult`.
1536+
*
1537+
* @param tpe type of the implicit parameter
1538+
* @param ctx current context
1539+
*/
1540+
def searchImplicit(tpe: Type)(implicit ctx: Context): ImplicitSearchResult
1541+
15091542
}

‎tests/neg-macros/delegate-match-1.check

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@@ -0,0 +1,7 @@
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-- Error: tests/neg-macros/delegate-match-1/Test_2.scala:6:2 -----------------------------------------------------------
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6 | f // error
4+
| ^
5+
| AmbiguousImplicits
6+
| both value a1 in class Test1 and value a2 in class Test1 match type A
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| This location is in code that was inlined at Test_2.scala:6

‎tests/neg-macros/delegate-match-1/Macro_1.scala

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@@ -0,0 +1,23 @@
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import scala.quoted._
2+
import scala.quoted.matching._
3+
4+
inline def f: Any = ${ fImpl }
5+
6+
private def fImpl given (qctx: QuoteContext): Expr[Unit] = {
7+
import qctx.tasty._
8+
searchImplicit(('[A]).unseal.tpe) match {
9+
case IsImplicitSearchSuccess(x) =>
10+
'{}
11+
case IsDivergingImplicit(x) => '{}
12+
error("DivergingImplicit\n" + x.explanation, rootPosition)
13+
'{}
14+
case IsNoMatchingImplicits(x) =>
15+
error("NoMatchingImplicits\n" + x.explanation, rootPosition)
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'{}
17+
case IsAmbiguousImplicits(x) =>
18+
error("AmbiguousImplicits\n" + x.explanation, rootPosition)
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'{}
20+
}
21+
}
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class A

‎tests/neg-macros/delegate-match-1/Test_2.scala

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@@ -0,0 +1,8 @@
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class Test1 extends App {
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implicit val a1: A = new A
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implicit val a2: A = new A
6+
f // error
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8+
}

‎tests/neg-macros/delegate-match-2.check

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-- Error: tests/neg-macros/delegate-match-2/Test_2.scala:5:2 -----------------------------------------------------------
3+
5 | f // error
4+
| ^
5+
| DivergingImplicit
6+
| method a1 in class Test produces a diverging implicit search when trying to match type A
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| This location is in code that was inlined at Test_2.scala:5

‎tests/neg-macros/delegate-match-2/Macro_1.scala

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import scala.quoted._
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import scala.quoted.matching._
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inline def f: Any = ${ fImpl }
5+
6+
private def fImpl given (qctx: QuoteContext): Expr[Unit] = {
7+
import qctx.tasty._
8+
searchImplicit(('[A]).unseal.tpe) match {
9+
case IsImplicitSearchSuccess(x) =>
10+
'{}
11+
case IsDivergingImplicit(x) => '{}
12+
error("DivergingImplicit\n" + x.explanation, rootPosition)
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'{}
14+
case IsNoMatchingImplicits(x) =>
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error("NoMatchingImplicits\n" + x.explanation, rootPosition)
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'{}
17+
case IsAmbiguousImplicits(x) =>
18+
error("AmbiguousImplicits\n" + x.explanation, rootPosition)
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'{}
20+
}
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}
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class A

‎tests/neg-macros/delegate-match-2/Test_2.scala

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class Test extends App {
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implicit def a1(implicit a: A): A = new A
5+
f // error
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}

‎tests/neg-macros/delegate-match-3.check

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-- Error: tests/neg-macros/delegate-match-3/Test_2.scala:3:2 -----------------------------------------------------------
3+
3 | f // error
4+
| ^
5+
| NoMatchingImplicits
6+
| no implicit values were found that match type A
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| This location is in code that was inlined at Test_2.scala:3

‎tests/neg-macros/delegate-match-3/Macro_1.scala

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@@ -0,0 +1,23 @@
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import scala.quoted._
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import scala.quoted.matching._
3+
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inline def f: Any = ${ fImpl }
5+
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private def fImpl given (qctx: QuoteContext): Expr[Unit] = {
7+
import qctx.tasty._
8+
searchImplicit(('[A]).unseal.tpe) match {
9+
case IsImplicitSearchSuccess(x) =>
10+
'{}
11+
case IsDivergingImplicit(x) => '{}
12+
error("DivergingImplicit\n" + x.explanation, rootPosition)
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'{}
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case IsNoMatchingImplicits(x) =>
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error("NoMatchingImplicits\n" + x.explanation, rootPosition)
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'{}
17+
case IsAmbiguousImplicits(x) =>
18+
error("AmbiguousImplicits\n" + x.explanation, rootPosition)
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'{}
20+
}
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}
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class A

‎tests/neg-macros/delegate-match-3/Test_2.scala

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class Test extends App {
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f // error
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}

‎tests/run-macros/quote-implicitMatch.check

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class scala.collection.immutable.TreeSet
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class scala.collection.immutable.HashSet
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B

‎tests/run-macros/quote-implicitMatch/Macro_1.scala

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import collection.immutable.TreeSet
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import collection.immutable.HashSet
3+
import scala.quoted._
4+
import scala.quoted.matching._
5+
6+
inline def f1[T]() = ${ f1Impl[T] }
7+
8+
def f1Impl[T: Type] given QuoteContext = {
9+
searchImplicitExpr[Ordering[T]] match {
10+
case Some(ord) => '{ new TreeSet[T]()($ord) }
11+
case _ => '{ new HashSet[T] }
12+
}
13+
}
14+
15+
class A
16+
class B
17+
18+
inline def g = ${ gImpl }
19+
20+
def gImpl given QuoteContext = {
21+
if (searchImplicitExpr[A].isDefined) '{ println("A") }
22+
else if (searchImplicitExpr[B].isDefined) '{ println("B") }
23+
else throw new MatchError("")
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}

‎tests/run-macros/quote-implicitMatch/Test_2.scala

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object Test extends App {
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implicitly[Ordering[String]]
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println(f1[String]().getClass)
6+
println(f1[AnyRef]().getClass)
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implicit val b: B = new B
9+
implicitly[B]
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g
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}

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