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, 40 insertions, 13 deletions

diff --git a/src/compiler/scala/tools/nsc/symtab/Symbols.scala b/src/compiler/scala/tools/nsc/symtab/Symbols.scala
index f62d221320..34a9dfa5cd 100644
--- a/src/compiler/scala/tools/nsc/symtab/Symbols.scala
+++ b/src/compiler/scala/tools/nsc/symtab/Symbols.scala
@@ -1185,7 +1185,7 @@ trait Symbols extends reflect.generic.Symbols { self: SymbolTable =>
         if (res == false) {
           val (f1, f2) = (this.sourceFile, that.sourceFile)
           if (f1 != null && f2 != null && f1.path != f2.path)
-            throw FatalError("Companions '" + this + "' and '" + that + "' must be defined in same file.")
+            throw InvalidCompanions(this, that)
         }
 
         res
@@ -2047,6 +2047,9 @@ trait Symbols extends reflect.generic.Symbols { self: SymbolTable =>
     // printStackTrace() // debug
   }
 
+  case class InvalidCompanions(sym1: Symbol, sym2: Symbol)
+  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) {
     assert((prev eq null) || phaseId(validFrom) > phaseId(prev.validFrom), this)
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index cac788906b..35b34ae5fd 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -1359,18 +1359,30 @@ trait Namers { self: Analyzer =>
    * does not work for classes defined inside methods.
    */
   def companionModuleOf(clazz: Symbol, context: Context) = {
-    var res = clazz.companionModule
-    if (res == NoSymbol)
-      res = context.lookup(clazz.name.toTermName, clazz.owner).suchThat(sym =>
-        sym.hasFlag(MODULE) && sym.isCoDefinedWith(clazz))
-    res
+    try {
+      var res = clazz.companionModule
+      if (res == NoSymbol)
+        res = context.lookup(clazz.name.toTermName, clazz.owner).suchThat(sym =>
+          sym.hasFlag(MODULE) && sym.isCoDefinedWith(clazz))
+        res
+    } catch {
+      case e: InvalidCompanions =>
+        context.error(clazz.pos, e.getMessage)
+        NoSymbol
+    }
   }
 
   def companionClassOf(module: Symbol, context: Context) = {
-    var res = module.companionClass
-    if (res == NoSymbol)
-      res = context.lookup(module.name.toTypeName, module.owner).suchThat(_.isCoDefinedWith(module))
-    res
+    try {
+      var res = module.companionClass
+      if (res == NoSymbol)
+        res = context.lookup(module.name.toTypeName, module.owner).suchThat(_.isCoDefinedWith(module))
+      res
+    } catch {
+      case e: InvalidCompanions =>
+        context.error(module.pos, e.getMessage)
+        NoSymbol
+    }
   }
 
   /** An explanatory note to be added to error messages
diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index e0e8efb007..d87cd571d8 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -1330,7 +1330,14 @@ 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 9bf63252cc..734964e9cf 100644
--- a/test/files/neg/bug1286.check
+++ b/test/files/neg/bug1286.check
@@ -1,2 +1,7 @@
-error: fatal error: Companions 'object Foo' and 'trait Foo' must be defined in same file.
-one error found
+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