Don't crash the compiler for the 'companions in...

Don't crash the compiler for the 'companions in different files'
error. This turned out to be pretty bad for the presentation compiler.
References #1286. Review by extempore

4 files changed, 29 insertions, 15 deletions

diff --git a/src/compiler/scala/tools/nsc/symtab/Symbols.scala b/src/compiler/scala/tools/nsc/symtab/Symbols.scala
index 9dec01fb7d..ef295acd02 100644
--- a/src/compiler/scala/tools/nsc/symtab/Symbols.scala
+++ b/src/compiler/scala/tools/nsc/symtab/Symbols.scala
@@ -1220,16 +1220,21 @@ trait Symbols extends reflect.generic.Symbols { self: SymbolTable =>
     /** Is this symbol defined in the same scope and compilation unit as `that' symbol?
      */
     def isCoDefinedWith(that: Symbol) =
-      (this.rawInfo ne NoType) &&
-      (this.owner == that.owner) && {
-        !this.owner.isPackageClass ||
-        (this.sourceFile eq null) ||
-        (that.sourceFile eq null) ||
-        (this.sourceFile == that.sourceFile) || {
-          // recognize companion object in separate file and fail, else compilation
-          // appears to succeed but highly opaque errors come later: see bug #1286
-          if (this.sourceFile.path != that.sourceFile.path)
+      (this.rawInfo ne NoType) && {
+        val res =
+          !this.owner.isPackageClass ||
+          (this.sourceFile eq null) ||
+          (that.sourceFile eq null) ||
+          (this.sourceFile eq that.sourceFile) ||
+          (this.sourceFile == that.sourceFile)
+
+        // recognize companion object in separate file and fail, else compilation
+        // appears to succeed but highly opaque errors come later: see bug #1286
+        if (res == false) {
+          val (f1, f2) = (this.sourceFile, that.sourceFile)
+          if (f1 != null && f2 != null && f1.path != f2.path)
             throw InvalidCompanions(this, that)
+        }
 
           false
         }
@@ -2103,9 +2108,7 @@ trait Symbols extends reflect.generic.Symbols { self: SymbolTable =>
   }
 
   case class InvalidCompanions(sym1: Symbol, sym2: Symbol)
-  extends Throwable("Companions '" + sym1 + "' and '" + sym2 + "' must be defined in same file") {
-      override def toString = getMessage
-  }
+  extends Throwable("Companions '" + sym1 + "' and '" + sym2 + "' must be defined in same file")
 
   /** A class for type histories */
   private sealed case class TypeHistory(var validFrom: Period, info: Type, prev: TypeHistory) {
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index 27f8df18b3..07cce81565 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -1382,7 +1382,7 @@ trait Namers { self: Analyzer =>
    * Finds the companion module of a class symbol. Calling .companionModule
    * does not work for classes defined inside methods.
    */
-  def companionModuleOf(clazz: Symbol, context: Context): Symbol = {
+  def companionModuleOf(clazz: Symbol, context: Context) = {
     try {
       var res = clazz.companionModule
       if (res == NoSymbol)
@@ -1396,7 +1396,7 @@ trait Namers { self: Analyzer =>
     }
   }
 
-  def companionClassOf(module: Symbol, context: Context): Symbol = {
+  def companionClassOf(module: Symbol, context: Context) = {
     try {
       var res = module.companionClass
       if (res == NoSymbol)
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 745809ccbb..1bf51973ba 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -1340,7 +1340,14 @@ trait Typers { self: Analyzer =>
 //      attributes(mdef)
       // initialize all constructors of the linked class: the type completer (Namer.methodSig)
       // might add default getters to this object. example: "object T; class T(x: Int = 1)"
-      val linkedClass = mdef.symbol.companionClass
+      val linkedClass =
+          try {
+            mdef.symbol.companionClass
+          } catch {
+            case e: InvalidCompanions =>
+              context.error(mdef.symbol.pos, e.getMessage)
+              NoSymbol
+          }
       if (linkedClass != NoSymbol)
         for (c <- linkedClass.info.decl(nme.CONSTRUCTOR).alternatives)
           c.initialize
diff --git a/test/files/neg/bug1286.check b/test/files/neg/bug1286.check
index d45d8094fd..734964e9cf 100644
--- a/test/files/neg/bug1286.check
+++ b/test/files/neg/bug1286.check
@@ -1,3 +1,7 @@
 a.scala:1: error: Companions 'object Foo' and 'trait Foo' must be defined in same file
 trait Foo {
       ^
+b.scala:1: error: Companions 'trait Foo' and 'object Foo' must be defined in same file
+object Foo extends Foo {
+       ^
+two errors found