[5.9][Macros] Requestify MacroExpansionExpr expansion

include/swift/AST/TypeCheckRequests.h

@@ -3930,6 +3930,26 @@ class ExpandMacroExpansionDeclRequest
   void noteCycleStep(DiagnosticEngine &diags) const;
 };
 
+/// Expand a 'MacroExpansionExpr',
+class ExpandMacroExpansionExprRequest
+    : public SimpleRequest<ExpandMacroExpansionExprRequest,
+                           Optional<unsigned>(MacroExpansionExpr *),
+                           RequestFlags::Cached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  Optional<unsigned>
+  evaluate(Evaluator &evaluator, MacroExpansionExpr *mee) const;
+
+public:
+  bool isCached() const { return true; }
+  void diagnoseCycle(DiagnosticEngine &diags) const;
+  void noteCycleStep(DiagnosticEngine &diags) const;
+};
+
 /// Expand all accessor macros attached to the given declaration.
 ///
 /// Produces the set of macro expansion buffer IDs.

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -439,6 +439,9 @@ SWIFT_REQUEST(TypeChecker, ExternalMacroDefinitionRequest,
 SWIFT_REQUEST(TypeChecker, ExpandMacroExpansionDeclRequest,
               ArrayRef<Decl *>(MacroExpansionDecl *),
               Cached, NoLocationInfo)
+SWIFT_REQUEST(TypeChecker, ExpandMacroExpansionExprRequest,
+              ArrayRef<Decl *>(MacroExpansionExpr *),
+              Cached, NoLocationInfo)
 SWIFT_REQUEST(TypeChecker, ExpandMemberAttributeMacros,
               ArrayRef<unsigned>(Decl *),
               Cached, NoLocationInfo)

include/swift/Basic/Lazy.h

@@ -14,13 +14,41 @@
 #define SWIFT_BASIC_LAZY_H
 
 #include <memory>
+#include <functional>
 
 #include "swift/Basic/Malloc.h"
 #include "swift/Basic/type_traits.h"
 #include "swift/Threading/Once.h"
 
 namespace swift {
 
+/// A template for lazy-initialized values.
+/// Usage:
+///
+///   LazyValue<std::string> value([]() { return createString(); })
+///   if (condition) {
+///     // 'createString()' is evaluated only when 'value` is dereferenced.
+///     doSomething(*value);
+///   }
+template <typename T, typename Initializer = std::function<T()>>
+class LazyValue {
+  Initializer Init;
+  llvm::Optional<T> Value;
+
+public:
+  LazyValue(Initializer Init) : Init(Init){};
+
+  T &get() {
+    if (!Value.hasValue()) {
+      Value = Init();
+    }
+    return Value.value();
+  }
+
+  T *operator->() { return &get(); }
+  T &operator*() { return get(); }
+};
+
 /// A template for lazily-constructed, zero-initialized, leaked-on-exit
 /// global objects.
 template <class T> class Lazy {

include/swift/Basic/StringExtras.h

@@ -490,7 +490,7 @@ class NullTerminatedStringRef {
 
   /// Create a null-terminated string, copying \p Str into \p A .
   template <typename Allocator>
-  NullTerminatedStringRef(StringRef Str, Allocator &A) : Ref() {
+  NullTerminatedStringRef(StringRef Str, Allocator &A) : Ref("") {
     if (Str.empty())
       return;
 

lib/AST/TypeCheckRequests.cpp

@@ -1833,6 +1833,22 @@ void ExpandMacroExpansionDeclRequest::noteCycleStep(DiagnosticEngine &diags) con
                  decl->getMacroName().getFullName());
 }
 
+void ExpandMacroExpansionExprRequest::diagnoseCycle(DiagnosticEngine &diags) const {
+  auto expr = std::get<0>(getStorage());
+  diags.diagnose(expr->getStartLoc(),
+                 diag::macro_expand_circular_reference,
+                 "freestanding",
+                 expr->getMacroName().getFullName());
+}
+
+void ExpandMacroExpansionExprRequest::noteCycleStep(DiagnosticEngine &diags) const {
+  auto expr = std::get<0>(getStorage());
+  diags.diagnose(expr->getStartLoc(),
+                 diag::macro_expand_circular_reference_through,
+                 "freestanding",
+                 expr->getMacroName().getFullName());
+}
+
 void ExpandAccessorMacros::diagnoseCycle(DiagnosticEngine &diags) const {
   auto decl = std::get<0>(getStorage());
   diags.diagnose(decl->getLoc(),

lib/Refactoring/Refactoring.cpp

@@ -8622,11 +8622,9 @@ bool RefactoringActionAddAsyncWrapper::performChange() {
 /// expression.
 static Optional<unsigned> getMacroExpansionBuffer(
     SourceManager &sourceMgr, MacroExpansionExpr *expansion) {
-  if (auto rewritten = expansion->getRewritten()) {
-    return sourceMgr.findBufferContainingLoc(rewritten->getStartLoc());
-  }
-
-  return None;
+  return evaluateOrDefault(
+      expansion->getDeclContext()->getASTContext().evaluator,
+      ExpandMacroExpansionExprRequest{expansion}, {});
 }
 
 /// Retrieve the macro expansion buffer for the given macro expansion

lib/Sema/CSApply.cpp

@@ -2937,13 +2937,14 @@ namespace {
 
         auto macro = cast<MacroDecl>(overload.choice.getDecl());
         ConcreteDeclRef macroRef = resolveConcreteDeclRef(macro, locator);
-        if (auto newExpr = expandMacroExpr(dc, expr, macroRef, expandedType)) {
-          auto expansion = new (ctx) MacroExpansionExpr(
-              dc, expr->getStartLoc(), DeclNameRef(macro->getName()),
-              DeclNameLoc(expr->getLoc()), SourceLoc(), { }, SourceLoc(),
-              nullptr, MacroRole::Expression, /*isImplicit=*/true, expandedType);
-          expansion->setMacroRef(macroRef);
-          expansion->setRewritten(newExpr);
+        auto expansion = new (ctx) MacroExpansionExpr(
+            dc, expr->getStartLoc(), DeclNameRef(macro->getName()),
+            DeclNameLoc(expr->getLoc()), SourceLoc(), {}, SourceLoc(), nullptr,
+            MacroRole::Expression, /*isImplicit=*/true, expandedType);
+        expansion->setMacroRef(macroRef);
+        (void)evaluateOrDefault(
+            ctx.evaluator, ExpandMacroExpansionExprRequest{expansion}, None);
+        if (expansion->getRewritten()) {
           cs.cacheExprTypes(expansion);
           return expansion;
         }
@@ -5386,23 +5387,19 @@ namespace {
       auto macro = cast<MacroDecl>(overload.choice.getDecl());
       ConcreteDeclRef macroRef = resolveConcreteDeclRef(macro, locator);
       E->setMacroRef(macroRef);
-
-      if (!cs.Options.contains(ConstraintSystemFlags::DisableMacroExpansions)) {
-        if (macro->getMacroRoles().contains(MacroRole::Expression)) {
-          if (auto newExpr = expandMacroExpr(dc, E, macroRef, expandedType)) {
-            E->setRewritten(newExpr);
-          }
-        }
-        // For a non-expression macro, expand it as a declaration.
-        else if (macro->getMacroRoles().contains(MacroRole::Declaration) ||
-                 macro->getMacroRoles().contains(MacroRole::CodeItem)) {
-          if (!E->getSubstituteDecl()) {
-            auto *med = E->createSubstituteDecl();
-            TypeChecker::typeCheckDecl(med);
-          }
-        }
-        // Other macro roles may also be encountered here, as they use
-        // `MacroExpansionExpr` for resolution. In those cases, do not expand.
+      E->setType(expandedType);
+
+      // FIXME: Expansion should be lazy.
+      // i.e. 'ExpandMacroExpansionExprRequest' should be sinked into
+      // 'getRewritten()', and performed on-demand.
+      if (!cs.Options.contains(ConstraintSystemFlags::DisableMacroExpansions) &&
+          // Do not expand macros inside macro arguments. For example for
+          // '#stringify(#assert(foo))' when typechecking `#assert(foo)`,
+          // we don't want to expand it.
+          llvm::none_of(makeArrayRef(ExprStack).drop_back(1),
+                       [](Expr *E) { return isa<MacroExpansionExpr>(E); })) {
+        (void)evaluateOrDefault(cs.getASTContext().evaluator,
+                                ExpandMacroExpansionExprRequest{E}, None);
       }
 
       cs.cacheExprTypes(E);