Closes #5452.

 Instead of trying to track the fallback attempts we rely on the
 context state to inform us which fallback is the last one.
 setError cannot always be called in NoBestMethodAlternativeError
 because inferMethodAlternative relies on side-effects.
 Review by @paulp.

5 files changed, 19 insertions, 8 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
index 6ee09d064f..6b67ee886e 100644
--- a/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala
@@ -713,10 +713,17 @@ trait ContextErrors {
           "constructor cannot be instantiated to expected type" + foundReqMsg(restpe, pt))
         setError(tree)
       }
-
-      def NoBestMethodAlternativeError(tree: Tree, argtpes: List[Type], pt: Type) =
+ 
+      def NoBestMethodAlternativeError(tree: Tree, argtpes: List[Type], pt: Type) = {
         issueNormalTypeError(tree,
           applyErrorMsg(tree, " cannot be applied to ", argtpes, pt))
+        // since inferMethodAlternative modifies the state of the tree 
+        // we have to set the type of tree to ErrorType only in the very last
+        // fallback action that is done in the inference (tracking it manually is error prone).
+        // This avoids entering infinite loop in doTypeApply.
+        // TODO: maybe we should do the same thing with inferExprAlternative.
+        if (implicitly[Context].reportErrors) setError(tree)
+      }
 
       def AmbiguousMethodAlternativeError(tree: Tree, pre: Type, best: Symbol,
             firstCompeting: Symbol, argtpes: List[Type], pt: Type) = {
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
index b97fbebec2..e1aa8b46eb 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala
@@ -1388,7 +1388,7 @@ trait Infer {
           NoBestExprAlternativeError(tree, pt)
         } else if (!competing.isEmpty) {
           if (secondTry) NoBestExprAlternativeError(tree, pt)
-          else { if (!pt.isErroneous) AmbiguousExprAlternativeError(tree, pre, best, competing.head, pt) }
+          else if (!pt.isErroneous) AmbiguousExprAlternativeError(tree, pre, best, competing.head, pt)
         } else {
 //          val applicable = alts1 filter (alt =>
 //            global.typer.infer.isWeaklyCompatible(pre.memberType(alt), pt))
@@ -1398,10 +1398,14 @@ trait Infer {
       }
     }
 
-    @inline private def inSilentMode(expr: Typer => Boolean): Boolean = {
-        val silentContext = context.makeSilent(context.ambiguousErrors)
-        val res = expr(newTyper(silentContext))
-        if (silentContext.hasErrors) false else res
+    @inline private def inSilentMode(context: Context)(expr: => Boolean): Boolean = {
+      val oldState = context.state
+      context.setBufferErrors()
+      val res = expr
+      val contextWithErrors = context.hasErrors
+      context.flushBuffer()
+      context.restoreState(oldState)
+      res && !contextWithErrors
     }
 
     // Checks against the name of the parameter and also any @deprecatedName.
@@ -1472,7 +1476,7 @@ trait Infer {
 
           val applicable = resolveOverloadedMethod(argtpes, {
             alts filter { alt =>
-              inSilentMode(typer0 => typer0.infer.isApplicable(undetparams, followApply(pre.memberType(alt)), argtpes, pt)) &&
+              inSilentMode(context)(isApplicable(undetparams, followApply(pre.memberType(alt)), argtpes, pt)) &&
               (!varArgsOnly || isVarArgsList(alt.tpe.params))
             }
           })
diff --git a/test/disabled/neg/t5452.check b/test/files/neg/t5452.check
index 2f35a45509..2f35a45509 100644
--- a/test/disabled/neg/t5452.check
+++ b/test/files/neg/t5452.check
diff --git a/test/disabled/neg/t5452.scala b/test/files/neg/t5452.scala
index 1032db7a4b..1032db7a4b 100644
--- a/test/disabled/neg/t5452.scala
+++ b/test/files/neg/t5452.scala
diff --git a/test/disabled/pos/spurious-overload.scala b/test/files/pos/spurious-overload.scala
index 9767a44eee..9767a44eee 100644
--- a/test/disabled/pos/spurious-overload.scala
+++ b/test/files/pos/spurious-overload.scala