Differentiate between Swift 5 and “Swift 6” #file

In -swift-version 5 and earlier, #file will continue to be a synonym for #filePath; in a future -swift-version (“Swift 6 mode”), it will become a synonym for #fileID. #file in libraries will be interpreted according to the language mode the library was compiled in, not the language mode its client uses.

Implement this behavior, tied to a frontend flag instead of a language version. We do so by splitting the old `MagicIdentifierLiteralExprKind::File` into two separate cases, `FileIDSpelledAsFile` and `FilePathSpelledAsFile`, and propagating this distinction throughout the AST. This seems cleaner than looking up the setting for the module the declaration belongs to every time we see `File`.

This doesn’t handle module interfaces yet; we’ll take care of those in a separate commit.

# Conflicts:
#	lib/Serialization/ModuleFormat.h

Author: beccadax

include/swift/AST/MagicIdentifierKinds.def

@@ -52,19 +52,27 @@
 // Magic string literals
 //
 
-/// The \c #file magic identifier literal.
-MAGIC_STRING_IDENTIFIER(File, "#file", PoundFileExpr)
-  MAGIC_IDENTIFIER_TOKEN(File, pound_file)
-  MAGIC_IDENTIFIER_DEPRECATED_TOKEN(File, kw___FILE__)
-
 /// The \c #fileID magic identifier literal.
 MAGIC_STRING_IDENTIFIER(FileID, "#fileID", PoundFileIDExpr)
   MAGIC_IDENTIFIER_TOKEN(FileID, pound_fileID)
 
+/// The \c #file magic identifier literal, written in code where it is
+/// a synonym for \c #fileID (i.e. "Swift 6 mode" code).
+MAGIC_STRING_IDENTIFIER(FileIDSpelledAsFile, "#file", PoundFileExpr)
+  // tok::pound_file is shared with FilePathSpelledAsFile; please write custom
+  // code paths for it.
+
 /// The \c #filePath magic identifier literal.
 MAGIC_STRING_IDENTIFIER(FilePath, "#filePath", PoundFilePathExpr)
   MAGIC_IDENTIFIER_TOKEN(FilePath, pound_filePath)
 
+/// The \c #file magic identifier literal, written in code where it is
+/// a synonym for \c #filePath (i.e. Swift 5 mode code).
+MAGIC_STRING_IDENTIFIER(FilePathSpelledAsFile, "#file", PoundFileExpr)
+  // tok::pound_file is shared with FileIDSpelledAsFile; please write custom
+  // code paths for it.
+  MAGIC_IDENTIFIER_DEPRECATED_TOKEN(FilePathSpelledAsFile, kw___FILE__)
+
 /// The \c #function magic identifier literal.
 MAGIC_STRING_IDENTIFIER(Function, "#function", PoundFunctionExpr)
   MAGIC_IDENTIFIER_TOKEN(Function, pound_function)

lib/IDE/CodeCompletion.cpp

@@ -4043,6 +4043,12 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
                             Optional<CodeCompletionLiteralKind> literalKind) {
       CodeCompletionKeywordKind kwKind;
       switch (magicKind) {
+      case MagicIdentifierLiteralExpr::FileIDSpelledAsFile:
+        kwKind = CodeCompletionKeywordKind::pound_file;
+        break;
+      case MagicIdentifierLiteralExpr::FilePathSpelledAsFile:
+        // Already handled by above case.
+        return;
 #define MAGIC_IDENTIFIER_TOKEN(NAME, TOKEN) \
       case MagicIdentifierLiteralExpr::NAME: \
         kwKind = CodeCompletionKeywordKind::TOKEN; \

lib/Parse/ParseExpr.cpp

@@ -1018,8 +1018,13 @@ static bool isValidTrailingClosure(bool isExprBasic, Parser &P){
 /// Map magic literal tokens such as #file to their
 /// MagicIdentifierLiteralExpr kind.
 static MagicIdentifierLiteralExpr::Kind
-getMagicIdentifierLiteralKind(tok Kind) {
+getMagicIdentifierLiteralKind(tok Kind, const LangOptions &Opts) {
   switch (Kind) {
+  case tok::pound_file:
+    // TODO: Enable by default at the next source break.
+    return Opts.EnableConcisePoundFile
+         ? MagicIdentifierLiteralExpr::FileIDSpelledAsFile
+         : MagicIdentifierLiteralExpr::FilePathSpelledAsFile;
 #define MAGIC_IDENTIFIER_TOKEN(NAME, TOKEN) \
   case tok::TOKEN: \
     return MagicIdentifierLiteralExpr::Kind::NAME;
@@ -1452,7 +1457,7 @@ ParserResult<Expr> Parser::parseExprPrimary(Diag<> ID, bool isExprBasic) {
 #define MAGIC_IDENTIFIER_DEPRECATED_TOKEN(NAME, TOKEN) case tok::TOKEN:
 #include "swift/AST/MagicIdentifierKinds.def"
   {
-    auto Kind = getMagicIdentifierLiteralKind(Tok.getKind());
+    auto Kind = getMagicIdentifierLiteralKind(Tok.getKind(), Context.LangOpts);
     auto replacement = MagicIdentifierLiteralExpr::getKindString(Kind);
 
     diagnose(Tok.getLoc(), diag::snake_case_deprecated,
@@ -1462,11 +1467,12 @@ ParserResult<Expr> Parser::parseExprPrimary(Diag<> ID, bool isExprBasic) {
   }
 
   // Cases for non-deprecated magic identifier tokens
+  case tok::pound_file:
 #define MAGIC_IDENTIFIER_DEPRECATED_TOKEN(NAME, TOKEN)
 #define MAGIC_IDENTIFIER_TOKEN(NAME, TOKEN) case tok::TOKEN:
 #include "swift/AST/MagicIdentifierKinds.def"
   {
-    auto Kind = getMagicIdentifierLiteralKind(Tok.getKind());
+    auto Kind = getMagicIdentifierLiteralKind(Tok.getKind(), Context.LangOpts);
     SyntaxKind SKind = getMagicIdentifierSyntaxKind(Kind);
 
     ExprContext.setCreateSyntax(SKind);

lib/SILGen/SILGenApply.cpp

@@ -4849,6 +4849,7 @@ RValue SILGenFunction::emitLiteral(LiteralExpr *literal, SGFContext C) {
 
     auto magicLiteral = cast<MagicIdentifierLiteralExpr>(literal);
     switch (magicLiteral->getKind()) {
+    case MagicIdentifierLiteralExpr::FileIDSpelledAsFile:
     case MagicIdentifierLiteralExpr::FileID: {
       std::string value = loc.isValid() ? getMagicFileIDString(loc) : "";
       builtinLiteralArgs = emitStringLiteral(*this, literal, value, C,
@@ -4858,7 +4859,7 @@ RValue SILGenFunction::emitLiteral(LiteralExpr *literal, SGFContext C) {
       break;
     }
 
-    case MagicIdentifierLiteralExpr::File:
+    case MagicIdentifierLiteralExpr::FilePathSpelledAsFile:
     case MagicIdentifierLiteralExpr::FilePath: {
       StringRef value = loc.isValid() ? getMagicFilePathString(loc) : "";
       builtinLiteralArgs = emitStringLiteral(*this, literal, value, C,

lib/Serialization/Deserialization.cpp

@@ -218,9 +218,10 @@ getActualDefaultArgKind(uint8_t raw) {
   CASE(Normal)
   CASE(Inherited)
   CASE(Column)
-  CASE(File)
   CASE(FileID)
   CASE(FilePath)
+  CASE(FileIDSpelledAsFile)
+  CASE(FilePathSpelledAsFile)
   CASE(Line)
   CASE(Function)
   CASE(DSOHandle)

lib/Serialization/ModuleFormat.h

@@ -55,7 +55,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 556; // Serialization of -implicit-dynamic
+const uint16_t SWIFTMODULE_VERSION_MINOR = 557; // #fileID
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -459,9 +459,10 @@ using ValueOwnershipField = BCFixed<2>;
 enum class DefaultArgumentKind : uint8_t {
   None = 0,
   Normal,
-  File,
   FileID,
   FilePath,
+  FileIDSpelledAsFile,
+  FilePathSpelledAsFile,
   Line,
   Column,
   Function,

lib/Serialization/Serialization.cpp

@@ -1119,9 +1119,10 @@ static uint8_t getRawStableDefaultArgumentKind(swift::DefaultArgumentKind kind)
   CASE(Normal)
   CASE(Inherited)
   CASE(Column)
-  CASE(File)
   CASE(FileID)
   CASE(FilePath)
+  CASE(FileIDSpelledAsFile)
+  CASE(FilePathSpelledAsFile)
   CASE(Line)
   CASE(Function)
   CASE(DSOHandle)

test/SILGen/Inputs/MagicIdentifierFileSwift.swift

@@ -0,0 +1 @@
+public func useLibrary(file: String = #file) {}

test/SILGen/magic_identifier_file.swift

@@ -1,8 +1,19 @@
-// RUN: %target-swift-emit-silgen -module-name Foo %/s | %FileCheck --check-prefixes=BOTH,ABSOLUTE %s
-// RUN: %target-swift-emit-silgen -enable-experimental-concise-pound-file -DNEEDS_CONCISE -module-name Foo %/s | %FileCheck --check-prefixes=BOTH,CONCISE %s
+// RUN: %empty-directory(%t)
 
-// FIXME: Once this feature becomes non-experimental, we should update existing
-// tests and delete this file.
+// Build library in Swift 5 mode:
+// RUN: %target-build-swift-dylib(%t/%target-library-name(MagicIdentifierFileSwift5)) -module-name MagicIdentifierFileSwift5 -emit-module-path %t/MagicIdentifierFileSwift5.swiftmodule -emit-module-interface-path %t/MagicIdentifierFileSwift5.swiftinterface -swift-version 5 -enable-library-evolution %S/Inputs/MagicIdentifierFileSwift.swift
+
+// Build library in "Swift 6" mode:
+// RUN: %target-build-swift-dylib(%t/%target-library-name(MagicIdentifierFileSwift6)) -module-name MagicIdentifierFileSwift6 -emit-module-path %t/MagicIdentifierFileSwift6.swiftmodule -emit-module-interface-path %t/MagicIdentifierFileSwift6.swiftinterface -swift-version 5 -enable-experimental-concise-pound-file -enable-library-evolution %S/Inputs/MagicIdentifierFileSwift.swift
+
+// Test in Swift 5 mode:
+// RUN: %target-swift-emit-silgen -I %t -module-name Foo %/s | %FileCheck --check-prefixes=BOTH,ABSOLUTE %s
+
+// Test in "Swift 6" mode:
+// RUN: %target-swift-emit-silgen -I %t -enable-experimental-concise-pound-file -module-name Foo %/s | %FileCheck --check-prefixes=BOTH,CONCISE %s
+
+import MagicIdentifierFileSwift5
+import MagicIdentifierFileSwift6
 
 func directUse() {
 // BOTH-LABEL: sil {{.*}} @$s3Foo9directUseyyF
@@ -13,11 +24,29 @@ func directUse() {
 
 func indirectUse() {
 // BOTH-LABEL: sil {{.*}} @$s3Foo11indirectUseyyF
-  fatalError()
+  useIndirectly()
 // ABSOLUTE: string_literal utf8 "SOURCE_DIR/test/SILGen/magic_identifier_file.swift"
 // CONCISE: string_literal utf8 "Foo/magic_identifier_file.swift"
 }
 
+func swift5LibraryUse() {
+// BOTH-LABEL: sil {{.*}} @$s3Foo16swift5LibraryUseyyF
+  MagicIdentifierFileSwift5.useLibrary()
+// BOTH: string_literal utf8 "SOURCE_DIR/test/SILGen/magic_identifier_file.swift"
+}
+
+func swift6LibraryUse() {
+// BOTH-LABEL: sil {{.*}} @$s3Foo16swift6LibraryUseyyF
+  MagicIdentifierFileSwift6.useLibrary()
+// BOTH: string_literal utf8 "Foo/magic_identifier_file.swift"
+}
+
+func stdlibUse() {
+// BOTH-LABEL: sil {{.*}} @$s3Foo9stdlibUseyyF
+  fatalError()
+// BOTH: string_literal utf8 "SOURCE_DIR/test/SILGen/magic_identifier_file.swift"
+}
+
 func forceUnwrap(_ x: ()?) {
 // BOTH-LABEL: sil {{.*}} @$s3Foo11forceUnwrapyyytSgF
   _ = x!
@@ -30,6 +59,8 @@ func forceTry(_ fn: () throws -> ()) {
 // BOTH: string_literal utf8 "Foo/magic_identifier_file.swift"
 }
 
+func useIndirectly(file: String = #file) {}
+
 // CONCISE-LABEL: // Mappings from '#fileID' to '#filePath':
 // CONCISE:       //   'Foo/magic_identifier_file.swift' => 'SOURCE_DIR/test/SILGen/magic_identifier_file.swift'