[SILGen] Expand magic literals like #file and #line to values in the outermost

source file.

Values inside macro expansion buffers are not useful.

(cherry picked from commit 9eb9ba2)

Author: hborla

lib/SILGen/SILGenApply.cpp

@@ -2124,6 +2124,28 @@ buildBuiltinLiteralArgs(SILGenFunction &SGF, SGFContext C,
   return args;
 }
 
+/// Returns the source location in the outermost source file
+/// for the given source location.
+///
+/// If the given source loc is in a macro expansion buffer, this
+/// method walks up the macro expansion buffer tree to the outermost
+/// source file. Otherwise, the method returns the given loc.
+static SourceLoc
+getLocInOutermostSourceFile(SourceManager &sourceManager, SourceLoc loc) {
+  auto outermostLoc = loc;
+  auto bufferID = sourceManager.findBufferContainingLoc(outermostLoc);
+
+  // Walk up the macro expansion buffer tree to the outermost
+  // source file.
+  while (auto generated = sourceManager.getGeneratedSourceInfo(bufferID)) {
+    auto node = ASTNode::getFromOpaqueValue(generated->astNode);
+    outermostLoc = node.getStartLoc();
+    bufferID = sourceManager.findBufferContainingLoc(outermostLoc);
+  }
+
+  return outermostLoc;
+}
+
 static inline PreparedArguments
 buildBuiltinLiteralArgs(SILGenFunction &SGF, SGFContext C,
                         MagicIdentifierLiteralExpr *magicLiteral) {
@@ -2153,7 +2175,8 @@ buildBuiltinLiteralArgs(SILGenFunction &SGF, SGFContext C,
 
   case MagicIdentifierLiteralExpr::Line:
   case MagicIdentifierLiteralExpr::Column: {
-    SourceLoc Loc = magicLiteral->getStartLoc();
+    auto Loc = getLocInOutermostSourceFile(SGF.getSourceManager(),
+                                           magicLiteral->getStartLoc());
     unsigned Value = 0;
     if (Loc.isValid()) {
       Value = magicLiteral->getKind() == MagicIdentifierLiteralExpr::Line
@@ -6002,7 +6025,10 @@ StringRef SILGenFunction::getMagicFunctionString() {
 
 StringRef SILGenFunction::getMagicFilePathString(SourceLoc loc) {
   assert(loc.isValid());
-  return getSourceManager().getDisplayNameForLoc(loc);
+  auto &sourceManager = getSourceManager();
+  auto outermostLoc = getLocInOutermostSourceFile(sourceManager, loc);
+
+  return getSourceManager().getDisplayNameForLoc(outermostLoc);
 }
 
 std::string SILGenFunction::getMagicFileIDString(SourceLoc loc) {

test/Macros/Inputs/syntax_macro_definitions.swift

@@ -1838,3 +1838,36 @@ public struct PeerValueWithSuffixNameMacro: PeerMacro {
     return ["var \(raw: identified.identifier.text)_peer: Int { 1 }"]
   }
 }
+
+public struct MagicFileMacro: ExpressionMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    return "#file"
+  }
+}
+
+public struct MagicLineMacro: ExpressionMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    return "(#line)"
+  }
+}
+
+public struct NestedMagicLiteralMacro: ExpressionMacro {
+  public static func expansion(
+    of node: some FreestandingMacroExpansionSyntax,
+    in context: some MacroExpansionContext
+  ) -> ExprSyntax {
+    return
+      """
+      {
+        print(#MagicFile)
+        print(#MagicLine)
+      }()
+      """
+  }
+}

test/Macros/magic_literal_expansion.swift

@@ -0,0 +1,28 @@
+// REQUIRES: swift_swift_parser, executable_test
+
+// RUN: %empty-directory(%t)
+// RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
+
+// RUN: %target-build-swift -enable-experimental-feature ExtensionMacros -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %s -o %t/main -module-name MacroUser -swift-version 5 -emit-tbd -emit-tbd-path %t/MacroUser.tbd -I %t
+// RUN: %target-codesign %t/main
+// RUN: %target-run %t/main | %FileCheck %s
+
+
+@freestanding(expression)
+macro MagicFile() -> String = #externalMacro(module: "MacroDefinition", type: "MagicFileMacro")
+
+@freestanding(expression)
+macro MagicLine() -> Int = #externalMacro(module: "MacroDefinition", type: "MagicLineMacro")
+
+// CHECK: magic_literal_expansion.swift
+print(#MagicFile)
+
+// CHECK: 21
+print(#MagicLine)
+
+@freestanding(expression)
+macro Nested() -> Void = #externalMacro(module: "MacroDefinition", type: "NestedMagicLiteralMacro")
+
+// CHECK: magic_literal_expansion.swift
+// CHECK: 28
+#Nested