fix: map name position to desugared version of named context bound (#22374)

resolves: #22335
This PR changes the positions so context bound name position is
correctly mapped in the desugaring:
```scala
def aa[T : Numeric as num]() = ??? // original code
def aa[T >: Nothing <: Any]()(using num: Numeric[T]): Nothing = ??? // desugared code, where position of `num` points to `num` in the original code
```
This also affects the cases where context bound is not named. The
definition position of `evidence$0` changed:
```scala
def aa[T : Numeric]() = ??? // original code
def aa[T >: Nothing <: Any]()(using evidence$0: Numeric[T]): Nothing = ??? // desugared code
// previously position of evidence$0 in original code
def aa[T : <<>>Numeric]() = ???
// after this PR
def aa[T : Numeric<<>>]() = ???
```
Which I think makes sense since if the was a name it would go after the
context bound

Author: tgodzik

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -272,18 +272,20 @@ object desugar {
       case ContextBounds(tbounds, ctxbounds) =>
         val isMember = evidenceFlags.isAllOf(DeferredGivenFlags)
         for bound <- ctxbounds do
-          val evidenceName = bound match
+          val (evidenceName, spanPoint) = bound match
             case ContextBoundTypeTree(_, _, ownName) if !ownName.isEmpty =>
-              ownName // if there is an explicitly given name, use it.
+              val realName = ownName.stripModuleClassSuffix.lastPart
+              (ownName, bound.span.end - realName.length) // if there is an explicitly given name, use it.
             case _ =>
               if Config.nameSingleContextBounds
                 && !isMember
                 && ctxbounds.tail.isEmpty
                 && Feature.enabled(Feature.modularity)
-              then tdef.name.toTermName
-              else freshName(bound)
+              then (tdef.name.toTermName, bound.span.point)
+              else (freshName(bound), bound.span.point)
           evidenceNames += evidenceName
-          val evidenceParam = ValDef(evidenceName, bound, EmptyTree).withFlags(evidenceFlags)
+          val evidenceParam =
+            ValDef(evidenceName, bound, EmptyTree).withFlags(evidenceFlags).withSpan(bound.span.withPoint(spanPoint))
           evidenceParam.pushAttachment(ContextBoundParam, ())
           evidenceBuf += evidenceParam
         tbounds

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -2265,7 +2265,8 @@ object Parsers {
           in.nextToken()
           ident()
         else EmptyTermName
-      ContextBoundTypeTree(t, pname, ownName)
+      val newSpan = t.span.withPoint(t.span.end).withEnd(in.lastOffset)
+      ContextBoundTypeTree(t, pname, ownName).withSpan(newSpan)
 
     /** ContextBounds     ::= ContextBound [`:` ContextBounds]
      *                      | `{` ContextBound {`,` ContextBound} `}`

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2466,7 +2466,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
   def typedContextBoundTypeTree(tree: untpd.ContextBoundTypeTree)(using Context): Tree =
     val tycon = typedType(tree.tycon)
     def spliced(tree: Tree) = untpd.TypedSplice(tree)
-    val tparam = untpd.Ident(tree.paramName).withSpan(tree.span)
+    val tparam = untpd.Ident(tree.paramName).withSpan(tree.span.withEnd(tree.span.point))
     if tycon.tpe.typeParams.nonEmpty then
       val tycon0 = tycon.withType(tycon.tpe.etaCollapse)
       typed(untpd.AppliedTypeTree(spliced(tycon0), tparam :: Nil))

presentation-compiler/test/dotty/tools/pc/tests/hover/HoverDefnSuite.scala

@@ -238,3 +238,27 @@ class HoverDefnSuite extends BaseHoverSuite:
          |""".stripMargin,
       "val foo: Int".hover
     )
+
+  @Test def `i22335` =
+    check(
+      """|def fromInt[T: Numeric as n@@um](t: Int): T = num.fromInt(t)
+         |""".stripMargin,
+      """|num: Numeric[T]
+         |""".stripMargin.hover
+    )
+
+  @Test def `i22335-2` =
+    check(
+      """|def showMax[X : {Numeric as nu@@m, Ordered as ord}](x: X, y: X): String = ???
+         |""".stripMargin,
+      """|num: Numeric[X]
+          |""".stripMargin.hover
+    )
+
+  @Test def `i22335-3` =
+    check(
+      """|def showMax[X : {Nu@@meric as num, Ordered as ord}](x: X, y: X): String = ???
+         |""".stripMargin,
+      """|type Numeric: Numeric
+         |""".stripMargin.hover
+    )

presentation-compiler/test/dotty/tools/pc/tests/inlayHints/InlayHintsSuite.scala

@@ -898,7 +898,7 @@ class InlayHintsSuite extends BaseInlayHintsSuite {
          |    import quotes.reflect.*
          |    Type.of[T] match
          |      case '[f] =>
-         |        val fr/*: TypeRepr<<scala/quoted/Quotes#reflectModule#TypeRepr#>>*/ = TypeRepr.of[T]/*(using evidence$1<<(3:23)>>)*/
+         |        val fr/*: TypeRepr<<scala/quoted/Quotes#reflectModule#TypeRepr#>>*/ = TypeRepr.of[T]/*(using evidence$1<<(3:27)>>)*/
          |""".stripMargin
    )
 

tests/pos/i20901/Foo.tastycheck

@@ -92,7 +92,7 @@ Trees (98 bytes, starting from <elided base index>):
     96:         STRINGconst 32 [<elided source file name>]
     98:
 
-Positions (73 bytes, starting from <elided base index>):
+Positions (75 bytes, starting from <elided base index>):
   lines: 7
   line sizes:
      38, 0, 23, 0, 10, 41, 0

tests/semanticdb/expect/Synthetic.expect.scala

@@ -30,7 +30,7 @@ class Synthetic/*<-example::Synthetic#*/ {
     null.asInstanceOf/*->scala::Any#asInstanceOf().*/[Int/*->scala::Int#*/ => Int/*->scala::Int#*/](2)
   }
 
-  class J/*<-example::Synthetic#J#*/[T/*<-example::Synthetic#J#[T]*/: /*<-example::Synthetic#J#evidence$1.*/Manifest/*->scala::Predef.Manifest#*//*->example::Synthetic#J#[T]*/] { val arr/*<-example::Synthetic#J#arr.*/ = Array/*->scala::Array.*/.empty/*->scala::Array.empty().*/[T/*->example::Synthetic#J#[T]*/] }
+  class J/*<-example::Synthetic#J#*/[T/*<-example::Synthetic#J#[T]*/: Manifest/*->scala::Predef.Manifest#*//*->example::Synthetic#J#[T]*//*<-example::Synthetic#J#evidence$1.*/] { val arr/*<-example::Synthetic#J#arr.*/ = Array/*->scala::Array.*/.empty/*->scala::Array.empty().*/[T/*->example::Synthetic#J#[T]*/] }
 
   class F/*<-example::Synthetic#F#*/
   implicit val ordering/*<-example::Synthetic#ordering.*/: Ordering/*->scala::package.Ordering#*/[F/*->example::Synthetic#F#*/] = ???/*->scala::Predef.`???`().*/

tests/semanticdb/metac.expect

@@ -2734,7 +2734,7 @@ Occurrences:
 [17:9..17:10): U <- example/Methods#m7().[U]
 [17:12..17:20): Ordering -> scala/math/Ordering#
 [17:12..17:20): Ordering -> example/Methods#m7().[U]
-[17:12..17:12): <- example/Methods#m7().(evidence$1)
+[17:20..17:20): <- example/Methods#m7().(evidence$1)
 [17:22..17:23): c <- example/Methods#m7().(c)
 [17:25..17:32): Methods -> example/Methods#
 [17:33..17:34): T -> example/Methods#[T]
@@ -3668,9 +3668,9 @@ Occurrences:
 [32:8..32:9): J <- example/Synthetic#J#
 [32:9..32:9): <- example/Synthetic#J#`<init>`().
 [32:10..32:11): T <- example/Synthetic#J#[T]
-[32:13..32:13): <- example/Synthetic#J#evidence$1.
 [32:13..32:21): Manifest -> scala/Predef.Manifest#
 [32:13..32:21): Manifest -> example/Synthetic#J#[T]
+[32:21..32:21): <- example/Synthetic#J#evidence$1.
 [32:29..32:32): arr <- example/Synthetic#J#arr.
 [32:35..32:40): Array -> scala/Array.
 [32:41..32:46): empty -> scala/Array.empty().