Remove llvm::Error include form Diagnostic.h

Saves ~400 related LLVM ADT. llvm/ADT/Error.h takes 90ms to parse.

$ diff -u <(sort thedeps-before.txt) <(sort thedeps-after.txt) \
    | grep '^[-+] ' | sort | uniq -c | sort -nr
    403 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm/Support/Error.h
    403 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm-c/Error.h
    397 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm/Support/Format.h
    397 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm/Support/Debug.h
    377 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm/ADT/StringExtras.h
    158 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm-c/ExternC.h
    138 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm/Support/ErrorOr.h
     13 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm/Support/raw_ostream.h
     13 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm/ADT/SmallString.h
      5 -    /usr/local/google/home/rnk/llvm-project/llvm/include/llvm/ADT/Twine.h

clang-tools-extra/clang-include-fixer/find-all-symbols/PathConfig.cpp

@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "PathConfig.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/Support/Path.h"
 
 namespace clang {

clang/include/clang/Basic/Diagnostic.h

@@ -26,7 +26,6 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/Compiler.h"
-#include "llvm/Support/Error.h"
 #include <cassert>
 #include <cstdint>
 #include <limits>
@@ -38,6 +37,10 @@
 #include <utility>
 #include <vector>
 
+namespace llvm {
+class Error;
+}
+
 namespace clang {
 
 class DeclContext;
@@ -1329,11 +1332,8 @@ inline DiagnosticBuilder DiagnosticsEngine::Report(SourceLocation Loc,
   return DiagnosticBuilder(this);
 }
 
-inline const DiagnosticBuilder &operator<<(const DiagnosticBuilder &DB,
-                                           llvm::Error &&E) {
-  DB.AddString(toString(std::move(E)));
-  return DB;
-}
+const DiagnosticBuilder &operator<<(const DiagnosticBuilder &DB,
+                                    llvm::Error &&E);
 
 inline DiagnosticBuilder DiagnosticsEngine::Report(unsigned DiagID) {
   return Report(SourceLocation(), DiagID);

clang/include/clang/Tooling/Refactoring/ASTSelection.h

@@ -13,6 +13,7 @@
 #include "clang/AST/Stmt.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/SourceLocation.h"
+#include "llvm/Support/raw_ostream.h"
 #include <vector>
 
 namespace clang {

clang/lib/AST/ExprConstant.cpp

@@ -54,6 +54,7 @@
 #include "clang/Basic/TargetInfo.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallBitVector.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Support/SaveAndRestore.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cstring>

clang/lib/AST/Interp/Disasm.cpp

@@ -16,6 +16,7 @@
 #include "Program.h"
 #include "clang/AST/DeclCXX.h"
 #include "llvm/Support/Compiler.h"
+#include "llvm/Support/Format.h"
 
 using namespace clang;
 using namespace clang::interp;

clang/lib/Basic/Diagnostic.cpp

@@ -61,6 +61,12 @@ const DiagnosticBuilder &clang::operator<<(const DiagnosticBuilder &DB,
   return DB;
 }
 
+const DiagnosticBuilder &clang::operator<<(const DiagnosticBuilder &DB,
+                                           llvm::Error &&E) {
+  DB.AddString(toString(std::move(E)));
+  return DB;
+}
+
 static void DummyArgToStringFn(DiagnosticsEngine::ArgumentKind AK, intptr_t QT,
                             StringRef Modifier, StringRef Argument,
                             ArrayRef<DiagnosticsEngine::ArgumentValue> PrevArgs,

clang/lib/Lex/LiteralSupport.cpp

@@ -25,6 +25,7 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/ConvertUTF.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <algorithm>
 #include <cassert>

clang/lib/Sema/CodeCompleteConsumer.cpp

@@ -23,6 +23,7 @@
 #include "clang/Sema/Sema.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/Casting.h"

clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp

@@ -23,6 +23,7 @@
 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace clang;

clang/lib/StaticAnalyzer/Checkers/FuchsiaHandleChecker.cpp

@@ -90,6 +90,7 @@
 #include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/SymExpr.h"
+#include "llvm/ADT/StringExtras.h"
 
 using namespace clang;
 using namespace ento;

clang/lib/StaticAnalyzer/Checkers/NonNullParamChecker.cpp

@@ -21,6 +21,7 @@
 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+#include "llvm/ADT/StringExtras.h"
 
 using namespace clang;
 using namespace ento;

clang/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp

@@ -20,6 +20,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace clang;

clang/lib/StaticAnalyzer/Core/BugReporter.cpp

@@ -51,6 +51,7 @@
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Support/Casting.h"

clang/lib/Tooling/Transformer/SourceCode.cpp

@@ -20,6 +20,7 @@
 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/Support/Errc.h"
+#include "llvm/Support/Error.h"
 #include <set>
 
 using namespace clang;