Let inlining report compiletime.error text

Author: som-snytt

compiler/src/dotty/tools/dotc/inlines/Inlines.scala

@@ -508,8 +508,13 @@ object Inlines:
           inContext(evCtx) {
             val evidence = evTyper.inferImplicitArg(tpe, callTypeArgs.head.span)
             evidence.tpe match
+              case fail: Implicits.LateMismatchedImplicit =>
+                val addendum = fail.errors match
+                  case Nil  => ""
+                  case errs => errs.map(_.msg).mkString("a search with errors:\n  ", "\n  ", "")
+                errorTree(call, evTyper.missingArgMsg(evidence, tpe, addendum))
               case fail: Implicits.SearchFailureType =>
-                errorTree(call, evTyper.missingArgMsg(evidence, tpe, ""))
+                errorTree(call, evTyper.missingArgMsg(evidence, tpe, where = ""))
               case _ =>
                 evidence
           }

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

@@ -616,6 +616,11 @@ object Implicits:
     def msg(using Context): Message =
       em"${errors.map(_.msg).mkString("\n")}"
   }
+
+  class LateMismatchedImplicit(ref: TermRef,
+                               expectedType: Type,
+                               argument: Tree,
+                               val errors: List[Diagnostic.Error]) extends MismatchedImplicit(ref, expectedType, argument)
 end Implicits
 
 import Implicits.*
@@ -1233,6 +1238,8 @@ trait Implicits:
               NoMatchingImplicitsFailure
             else if Splicer.inMacroExpansion && tpe <:< pt then
               SearchFailure(adapted.withType(new MacroErrorsFailure(ctx.reporter.allErrors.reverse, pt, argument)))
+            else if ctx.isAfterTyper then
+              SearchFailure(adapted.withType(LateMismatchedImplicit(ref, pt, argument, ctx.reporter.allErrors.reverse)))
             else
               SearchFailure(adapted.withType(new MismatchedImplicit(ref, pt, argument)))
         }

tests/neg/i15788.check

@@ -0,0 +1,32 @@
+-- Error: tests/neg/i15788.scala:39:13 ---------------------------------------------------------------------------------
+39 |  fff1[Test2] // error
+   |             ^
+   |             Field 'a' not found
+-- Error: tests/neg/i15788.scala:42:15 ---------------------------------------------------------------------------------
+42 |  summonInline[Test[Test2]].test // error
+   |               ^
+   |               Field 'a' not found
+-- [E172] Type Error: tests/neg/i15788.scala:45:6 ----------------------------------------------------------------------
+45 |  fff2[Test2] // error
+   |  ^^^^^^^^^^^
+   |  No given instance of type Test[Test2] was found for a search with errors:
+   |    Field 'a' not found.
+   |  I found:
+   |
+   |      Test.given_Test_A[Test2](
+   |        Test2.$asInstanceOf[
+   |          scala.deriving.Mirror.Product{
+   |            type MirroredMonoType = Test2; type MirroredType = Test2; type MirroredLabel = ("Test2" : String);
+   |              type MirroredElemTypes = (String, Int); type MirroredElemLabels = (("q" : String), ("w" : String))
+   |          }
+   |        ]
+   |      )
+   |
+   |  But given instance given_Test_A in object Test does not match type Test[Test2].
+   |--------------------------------------------------------------------------------------------------------------------
+   |Inline stack trace
+   |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+   |This location contains code that was inlined from i15788.scala:35
+35 |    summonInline[Test[P]].test
+   |    ^^^^^^^^^^^^^^^^^^^^^
+    --------------------------------------------------------------------------------------------------------------------

tests/neg/i15788.scala

@@ -0,0 +1,46 @@
+
+import scala.deriving.Mirror
+import scala.compiletime.*
+
+trait Test[A] {
+  def test: String
+}
+
+object Test {
+
+  inline def findA[T <: Tuple]: Unit =
+    inline erasedValue[T] match {
+      case _: EmptyTuple  => error("Field 'a' not found")
+      case _: ("a" *: tl) => ()
+      case _: (_ *: tl)   => findA[tl]
+    }
+
+  inline given [A <: Product] => (mm: Mirror.ProductOf[A]) => Test[A] = new {
+    override def test: String = {
+      findA[mm.MirroredElemLabels]
+      "test"
+    }
+  }
+}
+
+final case class Test1(a: String, b: Int)
+final case class Test2(q: String, w: Int)
+
+object Main {
+  inline def fff1[P <: Product](using ggg: Test[P]): String = {
+    ggg.test
+  }
+
+  inline def fff2[P <: Product]: String = {
+    summonInline[Test[P]].test
+  }
+
+  fff1[Test1]
+  fff1[Test2] // error
+
+  summonInline[Test[Test1]].test
+  summonInline[Test[Test2]].test // error
+
+  fff2[Test1]
+  fff2[Test2] // error
+}