SI-9314 No warn on ${nonid}

Use the sym test on an expr that happens to be a subset of
idents and is not in scope. Other `${ operator_* }` warn.

3 files changed, 36 insertions, 13 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 1b55618691..facb695447 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -105,7 +105,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
   // that are turned private by typedBlock
   private final val SYNTHETIC_PRIVATE = TRANS_FLAG
 
-  private final val InterpolatorCodeRegex  = """\$\{(.*?)\}""".r
+  private final val InterpolatorCodeRegex  = """\$\{\s*(.*?)\s*\}""".r
   private final val InterpolatorIdentRegex = """\$[$\w]+""".r // note that \w doesn't include $
 
   abstract class Typer(context0: Context) extends TyperDiagnostics with Adaptation with Tag with PatternTyper with TyperContextErrors {
@@ -5211,14 +5211,18 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
         def maybeWarn(s: String): Unit = {
           def warn(message: String)         = context.warning(lit.pos, s"possible missing interpolator: $message")
           def suspiciousSym(name: TermName) = context.lookupSymbol(name, _ => true).symbol
-          val suspiciousExpr                = InterpolatorCodeRegex findFirstMatchIn s
+          val suspiciousExprs               = InterpolatorCodeRegex findAllMatchIn s
           def suspiciousIdents              = InterpolatorIdentRegex findAllIn s map (s => suspiciousSym(TermName(s drop 1)))
-
-          if (suspiciousExpr.nonEmpty)
-            suspiciousExpr filter (!_.group(1).trim.isEmpty) foreach (_ =>
+          def isCheapIdent(expr: String)    = (Character.isJavaIdentifierStart(expr.charAt(0)) &&
+                                               expr.tail.forall(Character.isJavaIdentifierPart))
+          def warnableExpr(expr: String)    = !expr.isEmpty && (!isCheapIdent(expr) || isPlausible(suspiciousSym(TermName(expr))))
+
+          if (suspiciousExprs.nonEmpty) {
+            val exprs = (suspiciousExprs map (_ group 1)).toList
+            // short-circuit on leading ${}
+            if (!exprs.head.isEmpty && exprs.exists(warnableExpr))
               warn("detected an interpolated expression") // "${...}"
-            )
-          else
+          } else
             suspiciousIdents find isPlausible foreach (sym => warn(s"detected interpolated identifier `$$${sym.name}`")) // "$id"
         }
         lit match {
diff --git a/test/files/neg/t7848-interp-warn.check b/test/files/neg/t7848-interp-warn.check
index ad66ae1577..cc94cc81de 100644
--- a/test/files/neg/t7848-interp-warn.check
+++ b/test/files/neg/t7848-interp-warn.check
@@ -1,8 +1,8 @@
 t7848-interp-warn.scala:18: warning: possible missing interpolator: detected interpolated identifier `$foo`
-    "An important $foo message!"
+    "An important $foo message!"                              // warn on ident in scope
     ^
 t7848-interp-warn.scala:22: warning: possible missing interpolator: detected an interpolated expression
-    "A doubly important ${foo * 2} message!"
+    "A doubly important ${foo * 2} message!"                  // warn on some expr, see below
     ^
 t7848-interp-warn.scala:25: warning: possible missing interpolator: detected interpolated identifier `$bar`
   def i = s"Try using '${ "$bar" }' instead."                 // was: no warn on space test
@@ -10,6 +10,18 @@ t7848-interp-warn.scala:25: warning: possible missing interpolator: detected int
 t7848-interp-warn.scala:26: warning: possible missing interpolator: detected interpolated identifier `$bar`
   def j = s"Try using '${ "something like $bar" }' instead."  // warn
                           ^
+t7848-interp-warn.scala:32: warning: possible missing interpolator: detected an interpolated expression
+  def v = "${baz}${bar}"                                      // warn on second expr
+          ^
+t7848-interp-warn.scala:33: warning: possible missing interpolator: detected an interpolated expression
+  def w = "${ op_* }"                                         // warn, only cheap ident parsing
+          ^
+t7848-interp-warn.scala:34: warning: possible missing interpolator: detected an interpolated expression
+  def x = "${ bar }"                                          // warn, a cheap ident in scope
+          ^
+t7848-interp-warn.scala:36: warning: possible missing interpolator: detected an interpolated expression
+  def z = "${ baz * 3}"                                       // warn, no expr parsing
+          ^
 error: No warnings can be incurred under -Xfatal-warnings.
-four warnings found
+8 warnings found
 one error found
diff --git a/test/files/neg/t7848-interp-warn.scala b/test/files/neg/t7848-interp-warn.scala
index 635dd48c27..ceaf6c7d67 100644
--- a/test/files/neg/t7848-interp-warn.scala
+++ b/test/files/neg/t7848-interp-warn.scala
@@ -15,16 +15,23 @@ object Test {
   def bar = "bar"
   def f = {
     val foo = "bar"
-    "An important $foo message!"
+    "An important $foo message!"                              // warn on ident in scope
   }
   def g = {
     val foo = "bar"
-    "A doubly important ${foo * 2} message!"
+    "A doubly important ${foo * 2} message!"                  // warn on some expr, see below
   }
   def h = s"Try using '$$bar' instead."                       // no warn
   def i = s"Try using '${ "$bar" }' instead."                 // was: no warn on space test
   def j = s"Try using '${ "something like $bar" }' instead."  // warn
   def k = f"Try using '$bar' instead."                        // no warn on other std interps
   def p = "Template ${} {}"                                   // no warn on unlikely or empty expressions
-  def q = "${}$bar"                                           // disables subsequent checks!
+  def q = "${}$bar"                                           // disables subsequent checks! (a feature)
+  def r = "${}${bar}"                                         // disables subsequent checks! (a feature)
+
+  def v = "${baz}${bar}"                                      // warn on second expr
+  def w = "${ op_* }"                                         // warn, only cheap ident parsing
+  def x = "${ bar }"                                          // warn, a cheap ident in scope
+  def y = "${ baz }"                                          // no warn, cheap ident not in scope
+  def z = "${ baz * 3}"                                       // warn, no expr parsing
 }