Relax method signature matching under Mode.CheckBoundsOrSelfType

Author: dwijnand

compiler/src/dotty/tools/dotc/core/CheckRealizable.scala

@@ -131,8 +131,8 @@ class CheckRealizable(using Context) {
   /** `Realizable` if `tp` has good bounds, a `HasProblem...` instance
    *  pointing to a bad bounds member otherwise. "Has good bounds" means:
    *
-   *    - all type members have good bounds (except for opaque helpers)
-   *    - all refinements of the underlying type have good bounds (except for opaque companions)
+   *    - all type members have good bounds
+   *    - all refinements of the underlying type have good bounds
    *    - all base types are class types, and if their arguments are wildcards
    *      they have good bounds.
    *    - base types do not appear in multiple instances with different arguments.

compiler/src/dotty/tools/dotc/core/TypeComparer.scala

@@ -2134,11 +2134,16 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
       // resort to reflection to invoke the member. And Java reflection needs to know exact
       // erased parameter types. See neg/i12211.scala. Other reflection algorithms could
       // conceivably dispatch without knowing precise parameter signatures. One can signal
-      // this by inheriting from the `scala.reflect.SignatureCanBeImprecise` marker trait,
+      // this by inheriting from the `scala.Selectable.WithoutPreciseParameterTypes` marker trait,
       // in which case the signature test is elided.
+      // We also relax signature checking when checking bounds,
+      // for instance in tests/pos/i17222.izumi.min.scala
+      // the `go` method info as seen from `Foo` is `>: (in: Any): Unit <: (Nothing): Unit`
+      // So the parameter types conform but their signatures don't match.
       def sigsOK(symInfo: Type, info2: Type) =
         tp2.underlyingClassRef(refinementOK = true).member(name).exists
         || tp2.derivesFrom(defn.WithoutPreciseParameterTypesClass)
+        || ctx.mode.is(Mode.CheckBoundsOrSelfType)
         || symInfo.isInstanceOf[MethodType]
             && symInfo.signature.consistentParams(info2.signature)
 

tests/pos/i17222.izumi.min.scala

@@ -0,0 +1,7 @@
+class Foo:
+  type In
+  type Bar = { def go(in: In): Unit }
+  type False = false
+
+class Test:
+  def t1: Unit = valueOf[Foo#False]

tests/pos/i17222.izumi.rep/InspectorBase.scala

@@ -0,0 +1,59 @@
+package izumi.reflect.dottyreflection
+
+import scala.quoted.Quotes
+
+trait InspectorBase extends ReflectionUtil {
+
+  val qctx: Quotes
+  import qctx.reflect._
+
+  protected def shift: Int
+
+  // FIXME reimplement TrivialMacroLogger on Scala 3
+  inline def debug: debug = valueOf[debug]
+  final type debug = false
+
+  // println instead of report.info because report.info eats all the subsequent report.info's after first.
+  inline final protected def logStart(inline s: String): Unit = {
+    inline if (debug) println(" " * shift + currentPositionStr + s)
+  }
+
+  inline final protected def log(inline s: String): Unit = {
+    inline if (debug) println(" " * shift + currentPositionStr + " -> " + s)
+  }
+
+  inline final protected def logTpeAttrs[T](inline typeRepr: TypeRepr): Unit = {
+    inline if (debug) {
+      val tree = TypeTree.of(using typeRepr.asType)
+      val symbol = tree.symbol
+      System
+        .err.println(
+          currentPositionStr + ": " +
+          s"Attrs[${tree.show}]: type=${symbol.isType}, term=${symbol.isTerm}, packageDef=${symbol.isPackageDef}, classDef=${symbol.isClassDef}, typeDef=${symbol.isValDef}, defdef=${symbol.isDefDef}, bind=${symbol.isBind}, nosymbol=${symbol.isNoSymbol}"
+        )
+    }
+  }
+
+  private def currentPositionStr: String = {
+    val pos = qctx.reflect.Position.ofMacroExpansion
+    s"${pos.sourceFile.name}:${pos.endLine}"
+  }
+
+}
+
+object InspectorBase {
+
+  private[reflect] inline def ifDebug[A](inline f: => Unit): Unit = {
+    inline if (valueOf[InspectorBase#debug]) {
+//[error]              ^^^^^^^^^^^^^
+//[error] izumi.reflect.dottyreflection.InspectorBase is not a legal path
+//[error] since it has a member InternalTypeRefOrParamRef with possibly conflicting bounds Object{def underlying(ctx: Any): Nothing} <: ... <: Object{def underlying(ctx: Nothing): Matchable}
+      f
+    }
+  }
+
+  private[reflect] inline def log(inline shift: Int, s: String): Unit = {
+    inline if (valueOf[InspectorBase#debug]) println(" " * shift + " -> " + s)
+  }
+
+}