Correctly handle context functions in scaladoc

closes #14343

Author: KacperFKorban

scaladoc-testcases/src/tests/contextfunctions.scala

@@ -0,0 +1,4 @@
+package tests.contextfunctions
+
+val x: Int ?=> Float
+  = 5.0f

scaladoc/src/dotty/tools/scaladoc/tasty/TypesSupport.scala

@@ -182,18 +182,19 @@ trait TypesSupport:
           ++ plain(" ").l
           ++ inner(typeList.last)
         else if t.isFunctionType then
+          val arrow = if t.isContextFunctionType then " ?=> " else " => "
           typeList match
             case Nil =>
               Nil
             case Seq(rtpe) =>
-              plain("()").l ++ keyword(" => ").l ++ inner(rtpe)
+              plain("()").l ++ keyword(arrow).l ++ inner(rtpe)
             case Seq(arg, rtpe) =>
               val partOfSignature = arg match
                 case byName: ByNameType => plain("(").l ++ inner(byName) ++ plain(")").l
                 case _ => inner(arg)
-              partOfSignature ++ keyword(" => ").l ++ inner(rtpe)
+              partOfSignature ++ keyword(arrow).l ++ inner(rtpe)
             case args =>
-              plain("(").l ++ commas(args.init.map(inner)) ++ plain(")").l ++ keyword(" => ").l ++ inner(args.last)
+              plain("(").l ++ commas(args.init.map(inner)) ++ plain(")").l ++ keyword(arrow).l ++ inner(args.last)
         else if t.isTupleN then
           typeList match
             case Nil =>

scaladoc/test/dotty/tools/scaladoc/signatures/TranslatableSignaturesTestCases.scala

@@ -90,3 +90,5 @@ class ContextBounds extends SignatureTest("contextBounds", SignatureTest.all)
 class FBoundedTypeParameters extends SignatureTest("fboundedTypeParameters", SignatureTest.all)
 
 class Exports extends SignatureTest("exports2", SignatureTest.all, sourceFiles = List("exports1", "exports2"))
+
+class ContextFunctions extends SignatureTest("contextfunctions", SignatureTest.all)