Fixes undercompilation on local inheritance

### background

In sbt 0.13 days, we could ignore the relationship between two classes defined in the same `*.scala` source file, because they will be compiled anyway, and the invalidation was done at the source file level. With class-based namehashing, the invalidation is done at the class level, so we can no longer ignore inheritance relationship coming from the same source. This fact is acknowledged in the existence of `LocalDependencyByInheritance`, but we still have old assumptions scattered around the xsbt-dependency implementation.

### what this changes

This change changes two if expressions that was used to filter out dependency info coming from the same source.

### notes

One might wonder why it's necessary to keep the local inheritance info, if two classes involved are compiled together anyways. The answer is transitive dependencies. Using trait-trait-211 as example, `gg.table.ObjectConcatHelpers` was changed, eventually causing `xx.EvaluatorTestSupport` to invalidate. However, because of the missing same-source inheritance, it did not invalidate `xx.EvaluatorSpecification`. This meant that neither `xx.StringLibSpecs` was invalidated, and resulting to a runtime error.

Fixes sbt#417

internal/compiler-bridge/src/main/scala/xsbt/Dependency.scala

@@ -92,16 +92,21 @@ final class Dependency(val global: CallbackGlobal) extends LocateClassFile with
     }
 
     // Define processor reusing `processDependency` definition
-    val memberRef = processDependency(DependencyByMemberRef) _
-    val inheritance = processDependency(DependencyByInheritance) _
-    val localInheritance = processDependency(LocalDependencyByInheritance) _
+    val memberRef = processDependency(DependencyByMemberRef, false) _
+    val inheritance = processDependency(DependencyByInheritance, true) _
+    val localInheritance = processDependency(LocalDependencyByInheritance, true) _
+
+    @deprecated("Use processDependency that takes allowLocal.", "1.1.0")
+    def processDependency(context: DependencyContext)(dep: ClassDependency): Unit =
+      processDependency(context, true)(dep)
 
     /*
      * Handles dependency on given symbol by trying to figure out if represents a term
      * that is coming from either source code (not necessarily compiled in this compilation
      * run) or from class file and calls respective callback method.
      */
-    def processDependency(context: DependencyContext)(dep: ClassDependency): Unit = {
+    def processDependency(context: DependencyContext, allowLocal: Boolean)(
+        dep: ClassDependency): Unit = {
       val fromClassName = classNameAsString(dep.from)
 
       def binaryDependency(file: File, binaryClassName: String) =
@@ -133,11 +138,12 @@ final class Dependency(val global: CallbackGlobal) extends LocateClassFile with
           case None =>
             debuglog(Feedback.noOriginFileForExternalSymbol(dep.to))
         }
-      } else if (onSource.file != sourceFile) {
-        // Dependency is internal -- but from other file / compilation unit
+      } else if (onSource.file != sourceFile || allowLocal) {
+        // We cannot ignore dependencies coming from the same source file because
+        // the dependency info needs to propagate. See source-dependencies/trait-trait-211.
         val onClassName = classNameAsString(dep.to)
         callback.classDependency(onClassName, fromClassName, context)
-      } else () // Comes from the same file, ignore
+      }
     }
   }
 
@@ -227,7 +233,6 @@ final class Dependency(val global: CallbackGlobal) extends LocateClassFile with
       val depClass = enclOrModuleClass(dep)
       val dependency = ClassDependency(fromClass, depClass)
       if (!cache.contains(dependency) &&
-          fromClass.associatedFile != depClass.associatedFile &&
           !depClass.isRefinementClass) {
         process(dependency)
         cache.add(dependency)

zinc/src/sbt-test/source-dependencies/patMat-scope/test

@@ -12,9 +12,7 @@ $ sleep 1000
 $ exists target/classes/foo/SealedUsedInPatMatScope.class
 $ exists target/classes/foo/SealedNameUsedInDefaultScope.class
 
-# Default scopes should not change
-$ newer beforeFirstCompilation target/classes/foo/SealedNameUsedInDefaultScope.class
-# But PatMat and direct usage of child should be recompiled
+# PatMat and direct usage of child should be recompiled
 $ newer target/classes/foo/SealedUsedInPatMatScope.class beforeFirstCompilation
 
 # Change type of Sealed

zinc/src/sbt-test/source-dependencies/sealed/test

@@ -5,5 +5,5 @@ $ copy-file changes/A.scala A.scala
 
 # D.scala needs recompiling because the pattern match in D
 # is no longer exhaustive, which emits a warning
-> checkRecompilations 1 A B C E
-> checkRecompilations 2 D
+> checkRecompilations 1
+> checkRecompilations 2 A B C D E