[Macros] Parse top-level freestanding macros as MacroExpansionDecls when not

in script mode.

Author: hborla

include/swift/AST/DiagnosticsSema.def

@@ -6928,6 +6928,9 @@ ERROR(literal_type_in_macro_expansion,none,
 ERROR(invalid_macro_introduced_name,none,
       "declaration name %0 is not covered by macro %1",
       (DeclName, DeclName))
+ERROR(global_freestanding_macro_script,none,
+      "global freestanding macros not yet supported in script mode",
+      ())
 
 //------------------------------------------------------------------------------
 // MARK: Move Only Errors

lib/AST/ASTWalker.cpp

@@ -1343,9 +1343,6 @@ class Traversal : public ASTVisitor<Traversal, Expr*, Stmt*,
       }
       E->setRewritten(rewritten);
     }
-    if (auto *decl = E->getSubstituteDecl())
-      if (doIt(decl))
-        return nullptr;
     return E;
   }
 

lib/AST/Module.cpp

@@ -275,23 +275,6 @@ void SourceLookupCache::addToUnqualifiedLookupCache(Range decls,
 
     else if (auto *MED = dyn_cast<MacroExpansionDecl>(D))
       MayHaveAuxiliaryDecls.push_back(MED);
-
-    // Top-level macro expansion expressions can actually produce declarations,
-    // when they resolve to a substitute macro expansion decl.
-    else if (auto *TLCD = dyn_cast<TopLevelCodeDecl>(D)) {
-      for (auto node : TLCD->getBody()->getElements()) {
-        if (auto *E = node.dyn_cast<Expr *>()) {
-          if (auto *MEE = dyn_cast<MacroExpansionExpr>(E)) {
-            auto *MED = MEE->getSubstituteDecl();
-            if (!MED) {
-              MED = MEE->createSubstituteDecl();
-              MEE->setSubstituteDecl(MED);
-            }
-            MayHaveAuxiliaryDecls.push_back(MED);
-          }
-        }
-      }
-    }
   }
 }
 

lib/Parse/ParseDecl.cpp

@@ -4687,6 +4687,7 @@ bool swift::isKeywordPossibleDeclStart(const LangOptions &options,
   case tok::kw_subscript:
   case tok::kw_typealias:
   case tok::kw_var:
+  case tok::pound:
   case tok::pound_if:
   case tok::pound_warning:
   case tok::pound_error:
@@ -4798,6 +4799,11 @@ bool Parser::isStartOfSwiftDecl(bool allowPoundIfAttributes) {
     return isStartOfSwiftDecl(allowPoundIfAttributes);
   }
 
+  if (Tok.is(tok::pound) && peekToken().is(tok::identifier)) {
+    // Macro expansions at the top level are declarations.
+    return CurDeclContext->isModuleScopeContext() && !allowTopLevelCode();
+  }
+
   // Skip a #if that contains only attributes in all branches. These will be
   // parsed as attributes of a declaration, not as separate declarations.
   if (Tok.is(tok::pound_if) && allowPoundIfAttributes) {

lib/SILGen/SILGen.cpp

@@ -1984,13 +1984,6 @@ void SILGenModule::visitTopLevelCodeDecl(TopLevelCodeDecl *td) {
     if (auto *S = ESD.dyn_cast<Stmt*>()) {
       TopLevelSGF->emitStmt(S);
     } else if (auto *E = ESD.dyn_cast<Expr*>()) {
-      if (auto *MEE = dyn_cast<MacroExpansionExpr>(E)) {
-        if (auto *MED = MEE->getSubstituteDecl()) {
-          MED->visitAuxiliaryDecls([&](Decl *decl) {
-            visit(decl);
-          });
-        }
-      }
       TopLevelSGF->emitIgnoredExpr(E);
     } else {
       TopLevelSGF->visit(ESD.get<Decl*>());

lib/SILGen/SILGenDecl.cpp

@@ -1450,9 +1450,6 @@ void SILGenFunction::visitMacroExpansionDecl(MacroExpansionDecl *D) {
   MacroScope scope(*this, CleanupLocation(D), D,
                    D->getMacroName().getBaseIdentifier().str(),
                    D->getMacroRef().getDecl());
-  D->visitAuxiliaryDecls([&](Decl *decl) {
-    visit(decl);
-  });
   D->forEachExpandedExprOrStmt([&](ASTNode node) {
     if (auto *expr = node.dyn_cast<Expr *>())
       emitIgnoredExpr(expr);

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -3791,5 +3791,12 @@ ExpandMacroExpansionDeclRequest::evaluate(Evaluator &evaluator,
 
   // Otherwise, we treat it as a declaration macro.
   assert(roles.contains(MacroRole::Declaration));
+
+  // For now, restrict global freestanding macros in script mode.
+  if (dc->isModuleScopeContext() &&
+      dc->getParentSourceFile()->isScriptMode()) {
+    MED->diagnose(diag::global_freestanding_macro_script);
+  }
+
   return expandFreestandingMacro(MED);
 }

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -1178,7 +1178,6 @@ public struct DefineAnonymousTypesMacro: DeclarationMacro {
 
       class \(context.createUniqueName("name")) {
         func hello() {
-          \(body.statements)
         }
       }
       """,
@@ -1189,7 +1188,6 @@ public struct DefineAnonymousTypesMacro: DeclarationMacro {
         case banana
 
         func hello() {
-          \(body.statements)
         }
       }
       """

test/Macros/top_level_freestanding.swift

@@ -0,0 +1,37 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift -swift-version 5 -parse-as-library -enable-experimental-feature FreestandingMacros -I %swift-host-lib-dir -L %swift-host-lib-dir -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
+// RUNx: %target-swift-frontend -enable-experimental-feature FreestandingMacros -parse-as-library -emit-sil -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir %s -module-name MacroUser 2>&1 | %FileCheck --check-prefix CHECK-SIL %s
+// RUN: %target-typecheck-verify-swift -swift-version 5 -enable-experimental-feature FreestandingMacros -parse-as-library -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir -module-name MacroUser -DTEST_DIAGNOSTICS -swift-version 5
+// RUN: %target-build-swift -swift-version 5 -enable-experimental-feature FreestandingMacros -parse-as-library -load-plugin-library %t/%target-library-name(MacroDefinition) -I %swift-host-lib-dir -L %swift-host-lib-dir %s -o %t/main -module-name MacroUser -swift-version 5
+// RUN: %target-run %t/main | %FileCheck %s
+// REQUIRES: executable_test
+
+// FIXME: Swift parser is not enabled on Linux CI yet.
+// REQUIRES: OS=macosx
+
+// Test unqualified lookup from within a macro expansion
+@freestanding(declaration, names: named(StructWithUnqualifiedLookup))
+macro structWithUnqualifiedLookup() = #externalMacro(module: "MacroDefinition", type: "DefineStructWithUnqualifiedLookupMacro")
+
+let world = 3 // to be used by the macro expansion below
+
+#structWithUnqualifiedLookup
+
+func lookupGlobalFreestandingExpansion() {
+  // CHECK: 4
+  print(StructWithUnqualifiedLookup().foo())
+}
+
+@freestanding(declaration)
+macro anonymousTypes(_: () -> String) = #externalMacro(module: "MacroDefinition", type: "DefineAnonymousTypesMacro")
+
+#anonymousTypes { "hello" }
+
+// CHECK-SIL: sil hidden @$s9MacroUser03$s9A35User14anonymousTypesfMf0_4namefMu0_O5helloyyF : $@convention(method) ($s9MacroUser14anonymousTypesfMf0_4namefMu0_) -> () {
+
+@main
+struct Main {
+  static func main() {
+    lookupGlobalFreestandingExpansion()
+  }
+}