From cdffd55d12b42a55d31a7bde6e83808d48b670d8 Mon Sep 17 00:00:00 2001
From: Hamish Knight <hamish_knight@apple.com>
Date: Mon, 10 Nov 2025 15:57:33 +0000
Subject: [PATCH] [ClangImporter] Check for builtin conformance in
 `importNumericLiteral`

Make sure the destination type actually conforms to the corresponding
builtin literal protocol before attempting to import it. We may want
to consider allowing any type that conforms to the non-builtin literal
protocol, but I want to keep this patch low risk and just ensure we at
least don't crash for now.

rdar://156524292
---
 lib/ClangImporter/ImportMacro.cpp      | 25 +++++++++++++++++++++++
 test/ClangImporter/rdar156524292.swift | 28 ++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 test/ClangImporter/rdar156524292.swift

diff --git a/lib/ClangImporter/ImportMacro.cpp b/lib/ClangImporter/ImportMacro.cpp
index 4715e669f7a..717341b8bbf 100644
--- a/lib/ClangImporter/ImportMacro.cpp
+++ b/lib/ClangImporter/ImportMacro.cpp
@@ -125,6 +125,11 @@ static ValueDecl *importNumericLiteral(ClangImporter::Implementation &Impl,
         return nullptr;
     }
 
+    auto &ctx = DC->getASTContext();
+    auto *constantTyNominal = constantType->getAnyNominal();
+    if (!constantTyNominal)
+      return nullptr;
+
     if (auto *integer = dyn_cast<clang::IntegerLiteral>(parsed)) {
       // Determine the value.
       llvm::APSInt value{integer->getValue(), clangTy->isUnsignedIntegerType()};
@@ -140,6 +145,16 @@ static ValueDecl *importNumericLiteral(ClangImporter::Implementation &Impl,
         }
       }
 
+      // Make sure the destination type actually conforms to the builtin literal
+      // protocol before attempting to import, otherwise we'll crash since
+      // `createConstant` expects it to.
+      // FIXME: We ought to be careful checking conformance here since it can
+      // result in cycles. Additionally we ought to consider checking for the
+      // non-builtin literal protocol to allow any ExpressibleByIntegerLiteral
+      // type to be supported.
+      if (!ctx.getIntBuiltinInitDecl(constantTyNominal))
+        return nullptr;
+
       return createMacroConstant(Impl, MI, name, DC, constantType,
                                  clang::APValue(value),
                                  ConstantConvertKind::None,
@@ -158,6 +173,16 @@ static ValueDecl *importNumericLiteral(ClangImporter::Implementation &Impl,
         value.changeSign();
       }
 
+      // Make sure the destination type actually conforms to the builtin literal
+      // protocol before attempting to import, otherwise we'll crash since
+      // `createConstant` expects it to.
+      // FIXME: We ought to be careful checking conformance here since it can
+      // result in cycles. Additionally we ought to consider checking for the
+      // non-builtin literal protocol to allow any ExpressibleByFloatLiteral
+      // type to be supported.
+      if (!ctx.getFloatBuiltinInitDecl(constantTyNominal))
+        return nullptr;
+
       return createMacroConstant(Impl, MI, name, DC, constantType,
                                  clang::APValue(value),
                                  ConstantConvertKind::None,
diff --git a/test/ClangImporter/rdar156524292.swift b/test/ClangImporter/rdar156524292.swift
new file mode 100644
index 00000000000..c6cd5528921
--- /dev/null
+++ b/test/ClangImporter/rdar156524292.swift
@@ -0,0 +1,28 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+// RUN: %target-swift-frontend -typecheck -verify %t/main.swift -I %t -verify-additional-file %t/cmodule.h
+
+// REQUIRES: objc_interop
+// REQUIRES: OS=macosx
+
+//--- cmodule.h
+#import <CoreGraphics/CoreGraphics.h>
+#define intLiteralCGFloat ((CGFloat)0)
+// expected-note@-1 {{invalid numeric literal}}
+// expected-note@-2 {{macro 'intLiteralCGFloat' unavailable (cannot import)}}
+#define floatLiteralCGFloat ((CGFloat)0.0)
+// expected-note@-1 {{invalid numeric literal}}
+// expected-note@-2 {{macro 'floatLiteralCGFloat' unavailable (cannot import)}}
+
+//--- module.modulemap
+module CModule [system] {
+  header "cmodule.h"
+  export *
+}
+
+//--- main.swift
+import CModule
+
+// Make sure we don't crash when attempting to import these.
+_ = intLiteralCGFloat // expected-error {{cannot find 'intLiteralCGFloat' in scope}}
+_ = floatLiteralCGFloat // expected-error {{cannot find 'floatLiteralCGFloat' in scope}}