Refine condition when to not typecheck again

Only count errors that lead to an error type in some subtree as unrecoverable.

Author: odersky

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

@@ -344,7 +344,10 @@ object ProtoTypes {
       case _ => false
     }
 
-    /** Did an argument produce an error when typing? */
+    /** Did an argument produce an error when typing? This means: an error was reported
+     *  and a tree got an error type. Errors of adaptation whree a tree has a good type
+     *  but that type does not conform to the expected type are not counted.
+     */
     def hasErrorArg = !state.errorArgs.isEmpty
 
     private def cacheTypedArg(arg: untpd.Tree, typerFn: untpd.Tree => Tree, force: Boolean)(using Context): Tree = {
@@ -363,7 +366,7 @@ object ProtoTypes {
             targ = arg.withType(WildcardType)
           case _ =>
             targ = typerFn(arg)
-            if ctx.reporter.hasUnreportedErrors then
+            if ctx.reporter.hasUnreportedErrors && targ.existsSubTree(_.tpe.isError) then
               state.errorArgs += arg
             else
               state.typedArg = state.typedArg.updated(arg, targ)

tests/neg-custom-args/deprecation/t3235-minimal-v2.check

@@ -2,3 +2,15 @@
 3 |    assert(123456789.round == 123456789) // error
   |           ^^^^^^^^^^^^^^^
   |method round in class RichInt is deprecated since 2.11.0: this is an integer type; there is no reason to round it.  Perhaps you meant to call this on a floating-point value?
+-- Error: tests/neg-custom-args/deprecation/t3235-minimal.scala:4:16 ---------------------------------------------------
+4 |    assert(math.round(123456789) == 123456789) // error
+  |           ^^^^^^^^^^
+  |method round in package scala.math is deprecated since 2.11.0: This is an integer type; there is no reason to round it. Perhaps you meant to call this with a floating-point value?
+-- Error: tests/neg-custom-args/deprecation/t3235-minimal.scala:5:32 ---------------------------------------------------
+5 |    assert(1234567890123456789L.round == 1234567890123456789L) // error
+  |           ^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |method round in class RichLong is deprecated since 2.11.0: this is an integer type; there is no reason to round it.  Perhaps you meant to call this on a floating-point value?
+-- Error: tests/neg-custom-args/deprecation/t3235-minimal.scala:6:16 ---------------------------------------------------
+6 |    assert(math.round(1234567890123456789L) == 1234567890123456789L) // error
+  |           ^^^^^^^^^^
+  |method round in package scala.math is deprecated since 2.11.0: This is an integer type; there is no reason to round it. Perhaps you meant to call this with a floating-point value?

tests/neg-custom-args/deprecation/t3235-minimal-v2.scala

@@ -1,5 +1,8 @@
 object Test {
   def main(args: Array[String]): Unit = {
     assert(123456789.round == 123456789) // error
+    assert(math.round(123456789) == 123456789) // error
+    assert(1234567890123456789L.round == 1234567890123456789L) // error
+    assert(math.round(1234567890123456789L) == 1234567890123456789L) // error
   }
 }