Fix: dot notation using block params (#918)

Fixes #709 by changing `resolveOverloadedFunction` to also check
`BlockParam`s in scope. Notably, we only look up the first matching
symbol, as we do not (yet?) support overloading on block parameters.

Author: dvdvgt

effekt/shared/src/main/scala/effekt/Namer.scala

@@ -903,7 +903,10 @@ trait NamerOps extends ContextOps { Context: Context =>
 
     val syms2 = if (syms.isEmpty) scope.lookupOperation(id.path, id.name) else syms
 
-    if (syms2.nonEmpty) { assignSymbol(id, CallTarget(syms2.asInstanceOf)); true } else { false }
+    // lookup first block param and do not collect multiple since we do not (yet?) permit overloading on block parameters
+    val syms3 = if (syms2.isEmpty) List(scope.lookupFirstBlockParam(id.path, id.name)) else syms2
+
+    if (syms3.nonEmpty) { assignSymbol(id, CallTarget(syms3.asInstanceOf)); true } else { false }
   }
 
   /**

effekt/shared/src/main/scala/effekt/source/Tree.scala

@@ -646,7 +646,7 @@ object Named {
     // CallLike
     case Do         => symbols.Operation
     case Select     => symbols.Field
-    case MethodCall => symbols.Operation | symbols.CallTarget
+    case MethodCall => symbols.Operation | symbols.CallTarget | symbols.BlockParam
     case IdTarget   => symbols.TermSymbol
 
     // Others

effekt/shared/src/main/scala/effekt/symbols/Scope.scala

@@ -192,6 +192,13 @@ object scopes {
         namespace.terms.getOrElse(name, Set.empty).collect { case c: Callable if !c.isInstanceOf[Operation] => c }
       }.filter { namespace => namespace.nonEmpty }
 
+    def lookupFirstBlockParam(path: List[String], name: String)(using ErrorReporter): Set[BlockParam] =
+       first(path, scope) { namespace =>
+        namespace.terms.get(name).map(set => 
+          set.collect { case bp: BlockParam => bp }
+        )
+      }.getOrElse(Set.empty)
+
     // can be a term OR a type symbol
     def lookupFirst(path: List[String], name: String)(using E: ErrorReporter): Symbol =
       lookupFirstOption(path, name) getOrElse { E.abort(s"Could not resolve ${name}") }

effekt/shared/src/main/scala/effekt/typer/BoxUnboxInference.scala

@@ -87,20 +87,14 @@ object BoxUnboxInference extends Phase[NameResolved, NameResolved] {
       val vargsTransformed = vargs.map(rewriteAsExpr)
       val bargsTransformed = bargs.map(rewriteAsBlock)
 
-      val syms = m.definition match {
+      val hasMethods = m.definition match {
         // an overloaded call target
-        case symbols.CallTarget(syms) => syms.flatten
-        case s => C.panic(s"Not a valid method or function: ${id.name}")
-      }
-
-      val (funs, methods) = syms.partitionMap {
-        case t: symbols.Operation => Right(t)
-        case t: symbols.Callable => Left(t)
-        case t => C.abort(pp"Not a valid method or function: ${t}")
+        case symbols.CallTarget(syms) => syms.flatten.exists(b => b.isInstanceOf[symbols.Operation])
+        case s => false
       }
 
       // we prefer methods over uniform call syntax
-      if (methods.nonEmpty) {
+      if (hasMethods) {
         MethodCall(rewriteAsBlock(receiver), id, targs, vargsTransformed, bargsTransformed)
       } else {
         Call(IdTarget(id).inheritPosition(id), targs, rewriteAsExpr(receiver) :: vargsTransformed, bargsTransformed)

examples/pos/ufcs_blockparams.check

@@ -0,0 +1 @@
+true

examples/pos/ufcs_blockparams.effekt

@@ -0,0 +1,6 @@
+def refl[A](a: A) { eq: (A, A) => Bool }: Bool =
+  a.eq(a) && eq(a, a)
+
+def main() = {
+  println(refl(42) { (x, y) => x == y })
+}