[sourcekit] Retain semantic annotations across queries

Do not remove semantic annotations, so that if a client sends multiple
magic replacetext 0, 0, "" requests they will all return the same
result. This makes sourcekitd more robust around providing semantic
highlighting if the editor may make multiple queries for document
update.

rdar://64904029

Author: benlangmuir

test/SourceKit/Sema/sema_annotations_saved.swift

@@ -0,0 +1,10 @@
+func foo() {}
+foo()
+
+// RUN: %sourcekitd-test -req=open %s -- %s \
+// RUN:    == -req=edit -offset=0 -replace="" -length=0 %s \
+// RUN:    == -req=edit -offset=0 -replace="" -length=0 %s \
+// RUN:    == -req=edit -pos=3:1 -replace="foo()" -length=0 %s \
+// RUN:    == -req=edit -offset=0 -replace="" -length=0 %s \
+// RUN:    == -req=edit -offset=0 -replace="" -length=0 %s > %t.response
+// RUN: diff -u %s.response %t.response

test/SourceKit/Sema/sema_annotations_saved.swift.response

@@ -0,0 +1,66 @@
+{
+  key.annotations: [
+    {
+      key.kind: source.lang.swift.ref.function.free,
+      key.offset: 14,
+      key.length: 3
+    }
+  ],
+  key.diagnostic_stage: source.diagnostic.stage.swift.sema,
+  key.syntaxmap: [
+  ],
+  key.substructure: [
+  ]
+}
+{
+  key.annotations: [
+    {
+      key.kind: source.lang.swift.ref.function.free,
+      key.offset: 14,
+      key.length: 3
+    }
+  ],
+  key.diagnostic_stage: source.diagnostic.stage.swift.sema,
+  key.syntaxmap: [
+  ],
+  key.substructure: [
+  ]
+}
+{
+  key.annotations: [
+    {
+      key.kind: source.lang.swift.ref.function.free,
+      key.offset: 14,
+      key.length: 3
+    },
+    {
+      key.kind: source.lang.swift.ref.function.free,
+      key.offset: 20,
+      key.length: 3
+    }
+  ],
+  key.diagnostic_stage: source.diagnostic.stage.swift.sema,
+  key.syntaxmap: [
+  ],
+  key.substructure: [
+  ]
+}
+{
+  key.annotations: [
+    {
+      key.kind: source.lang.swift.ref.function.free,
+      key.offset: 14,
+      key.length: 3
+    },
+    {
+      key.kind: source.lang.swift.ref.function.free,
+      key.offset: 20,
+      key.length: 3
+    }
+  ],
+  key.diagnostic_stage: source.diagnostic.stage.swift.sema,
+  key.syntaxmap: [
+  ],
+  key.substructure: [
+  ]
+}

tools/SourceKit/lib/SwiftLang/SwiftEditor.cpp

@@ -659,7 +659,7 @@ class SwiftDocumentSemanticInfo :
   }
 
 private:
-  std::vector<SwiftSemanticToken> takeSemanticTokens(
+  std::vector<SwiftSemanticToken> getSemanticTokens(
       ImmutableTextSnapshotRef NewSnapshot);
 
   Optional<std::vector<DiagnosticEntryInfo>> getSemanticDiagnostics(
@@ -760,26 +760,28 @@ void SwiftDocumentSemanticInfo::readSemanticInfo(
 
   llvm::sys::ScopedLock L(Mtx);
 
-  Tokens = takeSemanticTokens(NewSnapshot);
+  Tokens = getSemanticTokens(NewSnapshot);
   Diags = getSemanticDiagnostics(NewSnapshot, ParserDiags);
 }
 
 std::vector<SwiftSemanticToken>
-SwiftDocumentSemanticInfo::takeSemanticTokens(
+SwiftDocumentSemanticInfo::getSemanticTokens(
     ImmutableTextSnapshotRef NewSnapshot) {
 
   llvm::sys::ScopedLock L(Mtx);
 
   if (SemaToks.empty())
     return {};
 
+  auto result = SemaToks;
+
   // Adjust the position of the tokens.
   TokSnapshot->foreachReplaceUntil(NewSnapshot,
     [&](ReplaceImmutableTextUpdateRef Upd) -> bool {
-      if (SemaToks.empty())
+      if (result.empty())
         return false;
 
-      auto ReplaceBegin = std::lower_bound(SemaToks.begin(), SemaToks.end(),
+      auto ReplaceBegin = std::lower_bound(result.begin(), result.end(),
           Upd->getByteOffset(),
           [&](const SwiftSemanticToken &Tok, unsigned StartOffset) -> bool {
             return Tok.ByteOffset+Tok.Length < StartOffset;
@@ -789,7 +791,7 @@ SwiftDocumentSemanticInfo::takeSemanticTokens(
       if (Upd->getLength() == 0) {
         ReplaceEnd = ReplaceBegin;
       } else {
-        ReplaceEnd = std::upper_bound(ReplaceBegin, SemaToks.end(),
+        ReplaceEnd = std::upper_bound(ReplaceBegin, result.end(),
             Upd->getByteOffset() + Upd->getLength(),
             [&](unsigned EndOffset, const SwiftSemanticToken &Tok) -> bool {
               return EndOffset < Tok.ByteOffset;
@@ -800,14 +802,14 @@ SwiftDocumentSemanticInfo::takeSemanticTokens(
       int Delta = InsertLen - Upd->getLength();
       if (Delta != 0) {
         for (std::vector<SwiftSemanticToken>::iterator
-               I = ReplaceEnd, E = SemaToks.end(); I != E; ++I)
+               I = ReplaceEnd, E = result.end(); I != E; ++I)
           I->ByteOffset += Delta;
       }
-      SemaToks.erase(ReplaceBegin, ReplaceEnd);
+      result.erase(ReplaceBegin, ReplaceEnd);
       return true;
     });
 
-  return std::move(SemaToks);
+  return result;
 }
 
 Optional<std::vector<DiagnosticEntryInfo>>