Requestify the #if computation using SwiftIfConfig

We're not caching this now, but it lets us dodge annoying layering
issues because ASTGen (where this is available) sits on top of the C++
parser, which needs to call it.

Author: DougGregor

include/swift/AST/ParseRequests.h

@@ -175,6 +175,23 @@ class IDEInspectionSecondPassRequest
   readDependencySource(const evaluator::DependencyRecorder &) const;
 };
 
+class EvaluateIfConditionRequest
+    : public SimpleRequest<EvaluateIfConditionRequest,
+          std::pair<bool, bool>(SourceFile *, SourceRange conditionRange,
+                                bool shouldEvaluate),
+                           RequestFlags::Uncached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  // Evaluation.
+  std::pair<bool, bool> evaluate(
+      Evaluator &evaluator, SourceFile *SF, SourceRange conditionRange,
+      bool shouldEvaluate) const;
+};
+
 /// The zone number for the parser.
 #define SWIFT_TYPEID_ZONE Parse
 #define SWIFT_TYPEID_HEADER "swift/AST/ParseTypeIDZone.def"

include/swift/AST/ParseTypeIDZone.def

@@ -31,3 +31,6 @@ SWIFT_REQUEST(Parse, ParseTopLevelDeclsRequest,
 SWIFT_REQUEST(Parse, ExportedSourceFileRequest,
               void *(const SourceFile *), Cached,
               NoLocationInfo)
+SWIFT_REQUEST(Parse, EvaluateIfConditionRequest,
+              (std::pair<bool, bool>)(SourceFile *, SourceRange, bool), Uncached,
+              NoLocationInfo)

include/swift/Basic/SourceLoc.h

@@ -163,6 +163,15 @@ class SourceRange {
   }
 
   SWIFT_DEBUG_DUMPER(dump(const SourceManager &SM));
+
+  friend size_t hash_value(SourceRange range) {
+    return llvm::hash_combine(range.Start, range.End);
+  }
+
+  friend void simple_display(raw_ostream &OS, const SourceRange &loc) {
+    // Nothing meaningful to print.
+  }
+
 };
 
 /// A half-open character-based source range.

lib/Parse/ParseIfConfig.cpp

@@ -767,13 +767,6 @@ static Expr *findAnyLikelySimulatorEnvironmentTest(Expr *Condition) {
 
 } // end anonymous namespace
 
-extern "C" intptr_t swift_ASTGen_evaluatePoundIfCondition(
-                        BridgedASTContext astContext,
-                        void *_Nonnull diagEngine,
-                        BridgedStringRef sourceFileBuffer,
-                        BridgedStringRef conditionText,
-                        bool);
-
 /// Call into the Swift implementation of #if condition evaluation.
 ///
 /// \returns std::nullopt if the Swift implementation is not available, or
@@ -786,21 +779,10 @@ static std::optional<std::pair<bool, bool>> evaluateWithSwiftIfConfig(
     bool shouldEvaluate
 ) {
 #if SWIFT_BUILD_SWIFT_SYNTAX
-  // FIXME: When we migrate to SwiftParser, use the parsed syntax tree.
-  auto &sourceMgr = parser.Context.SourceMgr;
-  StringRef sourceFileText =
-      sourceMgr.getEntireTextForBuffer(*parser.SF.getBufferID());
-  StringRef conditionText =
-      sourceMgr.extractText(Lexer::getCharSourceRangeFromSourceRange(
-          sourceMgr, conditionRange));
-  intptr_t evalResult = swift_ASTGen_evaluatePoundIfCondition(
-      parser.Context, &parser.Context.Diags, sourceFileText, conditionText,
-      shouldEvaluate
-  );
-
-  bool isActive = (evalResult & 0x01) != 0;
-  bool allowSyntaxErrors = (evalResult & 0x02) != 0;
-  return std::pair(isActive, allowSyntaxErrors);
+  return evaluateOrDefault(
+      parser.Context.evaluator,
+      EvaluateIfConditionRequest{&parser.SF, conditionRange, shouldEvaluate},
+      std::pair(false, false));
 #else
   return std::nullopt;
 #endif

lib/Sema/TypeChecker.cpp

@@ -23,6 +23,7 @@
 #include "TypeCheckType.h"
 #include "CodeSynthesis.h"
 #include "MiscDiagnostics.h"
+#include "swift/AST/ASTBridging.h"
 #include "swift/AST/ASTWalker.h"
 #include "swift/AST/ASTVisitor.h"
 #include "swift/AST/Attr.h"
@@ -765,3 +766,31 @@ bool TypeChecker::diagnoseInvalidFunctionType(
 
   return hadAnyError;
 }
+
+extern "C" intptr_t swift_ASTGen_evaluatePoundIfCondition(
+                        BridgedASTContext astContext,
+                        void *_Nonnull diagEngine,
+                        BridgedStringRef sourceFileBuffer,
+                        BridgedStringRef conditionText,
+                        bool);
+
+std::pair<bool, bool> EvaluateIfConditionRequest::evaluate(
+    Evaluator &evaluator, SourceFile *sourceFile, SourceRange conditionRange,
+    bool shouldEvaluate
+) const {
+  // FIXME: When we migrate to SwiftParser, use the parsed syntax tree.
+  ASTContext &ctx = sourceFile->getASTContext();
+  auto &sourceMgr = ctx.SourceMgr;
+  StringRef sourceFileText =
+      sourceMgr.getEntireTextForBuffer(*sourceFile->getBufferID());
+  StringRef conditionText =
+      sourceMgr.extractText(Lexer::getCharSourceRangeFromSourceRange(
+          sourceMgr, conditionRange));
+  intptr_t evalResult = swift_ASTGen_evaluatePoundIfCondition(
+      ctx, &ctx.Diags, sourceFileText, conditionText, shouldEvaluate
+  );
+
+  bool isActive = (evalResult & 0x01) != 0;
+  bool allowSyntaxErrors = (evalResult & 0x02) != 0;
+  return std::pair(isActive, allowSyntaxErrors);
+}