Fix overly conservative fingerprint bug & fix tests.

Author: David Ungar

lib/AST/AbstractSourceFileDepGraphFactory.cpp

@@ -79,6 +79,14 @@ void AbstractSourceFileDepGraphFactory::addAUsedDecl(
     const DependencyKey &defKey, const DependencyKey &useKey) {
   auto *defNode =
       g.findExistingNodeOrCreateIfNew(defKey, None, false /* = !isProvides */);
+  // If the depended-upon node is defined in this file, then don't
+  // create an arc to the user, when the user is the whole file.
+  // Otherwise, if the defNode's type-body fingerprint changes,
+  // the whole file will be marked as dirty, losing the benefit of the
+  // fingerprint.
+  if (defNode->getIsProvides() &&
+      useKey.getKind() == NodeKind::sourceFileProvide)
+    return;
   auto nullableUse = g.findExistingNode(useKey);
   assert(nullableUse.isNonNull() && "Use must be an already-added provides");
   auto *useNode = nullableUse.get();

test/Frontend/Inputs/type-fingerprint/a.swift

@@ -0,0 +1,5 @@
+struct A {
+  var x = 17
+}
+struct B {
+}

test/Frontend/Inputs/type-fingerprint/b0.swift

@@ -0,0 +1,4 @@
+struct A {
+}
+struct B {
+}

test/Frontend/Inputs/type-fingerprint/b1.swift

@@ -1,3 +1 @@
-func foo() {
-  B1()
-}
+

test/Frontend/Inputs/type-fingerprint/definesAB-after.swift

@@ -1,17 +1,22 @@
 {
-  "./a.swift": {
-    "object": "./a.o",
-    "swift-dependencies": "./a.swiftdeps"
-  },
-  "./b.swift": {
-    "object": "./b.o",
-    "swift-dependencies": "./b.swiftdeps"
-  },
-  "./main.swift": {
+  "main.swift": {
     "object": "./main.o",
     "swift-dependencies": "./main.swiftdeps"
   },
+  "definesAB.swift": {
+    "object": "./definesAB.o",
+    "swift-dependencies": "./definesAB.swiftdeps"
+  },
+  "usesA.swift": {
+    "object": "./usesA.o",
+    "swift-dependencies": "./usesA.swiftdeps"
+  },
+  "usesB.swift": {
+    "object": "./usesB.o",
+    "swift-dependencies": "./usesB.swiftdeps"
+  },
   "": {
     "swift-dependencies": "./main~buildrecord.swiftdeps"
   }
 }
+

test/Frontend/Inputs/type-fingerprint/definesAB-before.swift

@@ -0,0 +1 @@
+let a = A()

test/Frontend/Inputs/type-fingerprint/main.swift

@@ -0,0 +1 @@
+let b = B()