Merge pull request scala#6612 from adriaanm/pr6580-pt1

Faster implicit search: lazier error messages

Author: adriaanm

src/compiler/scala/tools/nsc/typechecker/ContextErrors.scala

@@ -97,7 +97,9 @@ trait ContextErrors {
 
     def issueTypeError(err: AbsTypeError)(implicit context: Context): Unit = { context.issue(err) }
 
-    def typeErrorMsg(found: Type, req: Type) = "type mismatch" + foundReqMsg(found, req)
+    def typeErrorMsg(context: Context, found: Type, req: Type) =
+      if (context.openImplicits.nonEmpty && !settings.XlogImplicits.value) "type mismatch"
+      else "type mismatch" + foundReqMsg(found, req)
   }
 
   def notAnyRefMessage(found: Type): String = {
@@ -208,7 +210,7 @@ trait ContextErrors {
         assert(!foundType.isErroneous, s"AdaptTypeError - foundType is Erroneous: $foundType")
         assert(!req.isErroneous, s"AdaptTypeError - req is Erroneous: $req")
 
-        issueNormalTypeError(callee, withAddendum(callee.pos)(typeErrorMsg(foundType, req)))
+        issueNormalTypeError(callee, withAddendum(callee.pos)(typeErrorMsg(context, foundType, req)))
         infer.explainTypes(foundType, req)
       }
 
@@ -1106,7 +1108,7 @@ trait ContextErrors {
       }
 
       def NoBestExprAlternativeError(tree: Tree, pt: Type, lastTry: Boolean) = {
-        issueNormalTypeError(tree, withAddendum(tree.pos)(typeErrorMsg(tree.symbol.tpe, pt)))
+        issueNormalTypeError(tree, withAddendum(tree.pos)(typeErrorMsg(context, tree.symbol.tpe, pt)))
         setErrorOnLastTry(lastTry, tree)
       }
 
@@ -1373,7 +1375,7 @@ trait ContextErrors {
                sm"""|Note that implicit conversions are not applicable because they are ambiguous:
                     |${coreMsg}are possible conversion functions from $found to $req"""
           }
-          typeErrorMsg(found, req) + (
+          typeErrorMsg(context, found, req) + (
             if (explanation == "") "" else "\n" + explanation
           )
         }

src/compiler/scala/tools/nsc/typechecker/Implicits.scala

@@ -410,7 +410,7 @@ trait Implicits {
 
     def pos = if (pos0 != NoPosition) pos0 else tree.pos
 
-    def failure(what: Any, reason: String, pos: Position = this.pos): SearchResult = {
+    @inline final def failure(what: Any, reason: => String, pos: Position = this.pos): SearchResult = {
       if (settings.XlogImplicits)
         reporter.echo(pos, what+" is not a valid implicit value for "+pt+" because:\n"+reason)
       SearchFailure
@@ -673,7 +673,7 @@ trait Implicits {
       val itree1 = if (isBlackbox(info.sym)) suppressMacroExpansion(itree0) else itree0
       typingLog("considering", typeDebug.ptTree(itree1))
 
-      def fail(reason: String): SearchResult = failure(itree0, reason)
+      @inline def fail(reason: => String): SearchResult = failure(itree0, reason)
       def fallback = typed1(itree1, EXPRmode, wildPt)
       try {
         val itree2 = if (!isView) fallback else pt match {
@@ -734,7 +734,7 @@ trait Implicits {
             info.sym.fullLocationString, itree2.symbol.fullLocationString))
         else {
           val tvars = undetParams map freshVar
-          def ptInstantiated = pt.instantiateTypeParams(undetParams, tvars)
+          val ptInstantiated = pt.instantiateTypeParams(undetParams, tvars)
 
           if (matchesPt(itree3.tpe, ptInstantiated, undetParams)) {
             if (tvars.nonEmpty)