Compare erasedness of parameters in the TypeComparer

Author: natsukagami

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

@@ -2117,7 +2117,14 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
       case nil =>
         formals2.isEmpty
     }
-    loop(tp1.paramInfos, tp2.paramInfos)
+    // Check if methods are erased, then the erased parameters match
+    val erasedValid = if tp1.isErasedMethod && tp1.isErasedMethod then
+                        val comp1 = tp1.companion.asInstanceOf[ErasedMethodCompanion]
+                        val comp2 = tp2.companion.asInstanceOf[ErasedMethodCompanion]
+                        comp1.isErased == comp2.isErased
+                      else !tp1.isErasedMethod && !tp2.isErasedMethod
+
+    erasedValid && loop(tp1.paramInfos, tp2.paramInfos)
   }
 
   /** Do the parameter types of `tp1` and `tp2` match in a way that allows `tp1`

tests/neg-custom-args/erased/multiple-args-consume.scala

@@ -0,0 +1,13 @@
+def foo(erased x: Int, y: Int) = y
+def bar(x: Int, erased y: Int) = x
+
+def consumeFoo(f: (erased x: Int, y: Int) => Int) = f(0, 1)
+
+val fooF: (erased x: Int, y: Int) => Int = foo
+val barF: (x: Int, erased y: Int) => Int = bar
+
+val a = consumeFoo(foo) // ok
+val b = consumeFoo(bar) // error
+
+val c = consumeFoo(fooF) // ok
+val d = consumeFoo(barF) // error

tests/neg-custom-args/erased/multiple-args.scala

@@ -0,0 +1,11 @@
+def foo(x: Int, erased y: Int): Int = x
+def bar(erased x: Int, y: Int): Int = y
+
+val fooF: (x: Int, erased y: Int) => Int = foo
+
+val fooG: (erased x: Int, y: Int) => Int = foo // error
+
+val barF: (x: Int, erased y: Int) => Int = bar // error
+
+val barG: (erased x: Int, y: Int) => Int = bar
+