SI-8525 Add -Xlint:-warn-missing-interpolator

Turn off lint warnings with negating prefix, and add a lint-only
warning for the infamously nagging "Did you forget the interpolator?"

That message is made more dignified.

Without `-Xlint:false`, there is no mechanism to turn off
anonymous linters once `-Xlint` is selected.

1 files changed, 17 insertions, 7 deletions

diff --git a/src/compiler/scala/tools/nsc/settings/Warnings.scala b/src/compiler/scala/tools/nsc/settings/Warnings.scala
index ae2696accf..f1ed45a2a0 100644
--- a/src/compiler/scala/tools/nsc/settings/Warnings.scala
+++ b/src/compiler/scala/tools/nsc/settings/Warnings.scala
@@ -31,9 +31,10 @@ trait Warnings {
     warnNullaryOverride,
     warnNullaryUnit,
     warnAdaptedArgs,
-    warnInferAny
+    warnInferAny,
     // warnUnused       SI-7712, SI-7707 warnUnused not quite ready for prime-time
     // warnUnusedImport currently considered too noisy for general use
+    warnMissingInterpolator
   )
 
   private lazy val warnSelectNullable = BooleanSetting("-Xcheck-null", "This option is obsolete and does nothing.")
@@ -50,23 +51,32 @@ trait Warnings {
   val warnUnused           = BooleanSetting   ("-Ywarn-unused", "Warn when local and private vals, vars, defs, and types are are unused")
   val warnUnusedImport     = BooleanSetting   ("-Ywarn-unused-import", "Warn when imports are unused")
 
+  // Lint warnings that are not -Y
+  val warnMissingInterpolator = new BooleanSetting("warn-missing-interpolator", "Warn when a string literal appears to be missing an interpolator id.")
+
   // Warning groups.
   val lint                 = {
     // Boolean setting for testing if lint is on; not "added" to option processing
     val xlint = new BooleanSetting("-Xlint", "Enable recommended additional warnings.")
-    val lintables = (lintWarnings map (_.name drop 2)).sorted
+    def lintables = (lintWarnings map (_.name stripPrefix "-Y")).sorted
+    def isAnon(b: BooleanSetting) = !(b.name startsWith "-")
+    def setPolitely(b: BooleanSetting, v: Boolean) = if (!b.isSetByUser) b.value = v
+    def set(w: String, v: Boolean) = lintWarnings find (_.name.stripPrefix("-Y") == w) foreach (b => setPolitely(b, v))
+    val Neg = "-"
     def propagate(ss: List[String]): Unit = ss match {
-      case w :: rest => lintWarnings find (_.name == s"-Y$w") foreach (_.value = true) ; propagate(rest)
-      case Nil         => ()
+      case w :: rest => if (w startsWith Neg) set(w stripPrefix Neg, false) else set(w, true) ; propagate(rest)
+      case Nil       => ()
     }
-    def enableAll(): Unit = {   // enable lint and the group
+    // enable lint and the group, honoring previous -Y settings
+    def enableAll(): Unit = {
       xlint.value = true
-      for (s <- lintWarnings if !s.isSetByUser) s.value = true
+      for (s <- lintWarnings) setPolitely(s, true)
     }
     // The command option
-    MultiChoiceSetting("-Xlint", "warning", "Enable recommended additional warnings", lintables, enableAll) withPostSetHook { x =>
+    MultiChoiceSetting("-Xlint", "warning", "Enable recommended additional warnings", choices = lintables, default = enableAll) withPostSetHook { x =>
       propagate(x.value)      // enabling the selections (on each append to value)
       xlint.value = true      // only enables lint, not the group
+      for (b <- lintWarnings if isAnon(b) && !b.isSetByUser) b.value = true   // init anonymous settings (but not if disabled)
     }
     xlint
   }