Workaround compiler issue

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/BidirectionalMap.swift

@@ -26,9 +26,9 @@ public struct BidirectionalMap<T1: Hashable, T2: Hashable>: Equatable, Sequence
       return value
     }
     set {
-      if let newValue = newValue {
-        map1[key] = newValue
-        map2[newValue] = key
+      if let someNewValue = newValue {
+        map1[key] = someNewValue
+        map2[someNewValue] = key
         return
       }
       if let oldValue = map1.removeValue(forKey: key) {
@@ -45,9 +45,9 @@ public struct BidirectionalMap<T1: Hashable, T2: Hashable>: Equatable, Sequence
       return value
     }
     set {
-      if let newValue = newValue {
-        map2[key] = newValue
-        map1[newValue] = key
+      if let someNewValue = newValue {
+        map2[key] = someNewValue
+        map1[someNewValue] = key
         return
       }
       if let oldValue = map2.removeValue(forKey: key) {

Sources/SwiftDriver/IncrementalCompilation/InitialStateComputer.swift

@@ -126,17 +126,17 @@ extension IncrementalCompilationState.InitialStateComputer {
   ) -> (ModuleDependencyGraph, Set<TypedVirtualPath>)?
   {
     let dependencyGraphPath = buildRecordInfo.dependencyGraphPath
-    let graph: ModuleDependencyGraph?
+    let graphIfPresent: ModuleDependencyGraph?
     do {
-      graph = try ModuleDependencyGraph.read( from: dependencyGraphPath, info: self)
+      graphIfPresent = try ModuleDependencyGraph.read( from: dependencyGraphPath, info: self)
     }
     catch {
       diagnosticEngine.emit(
         warning: "Could not read \(dependencyGraphPath), will not do cross-module incremental builds")
       reporter?.reportDisablingIncrementalBuild("Could not read priors from \(dependencyGraphPath)")
       return nil
     }
-    guard let graph = graph
+    guard let graph = graphIfPresent
     else {
       return buildInitialGraphFromSwiftDepsAndCollectInputsInvalidatedByChangedExternals()
     }