Merge pull request #75983 from etcwilde/ewilde/error-on-missing-compiler

CMake: Improving missing compiler error message

Author: etcwilde

CMakeLists.txt

@@ -968,6 +968,13 @@ if(SWIFT_INCLUDE_TOOLS AND SWIFT_BUILD_SWIFT_SYNTAX)
   if(SWIFT_HOST_VARIANT_SDK MATCHES "LINUX|OPENBSD|FREEBSD" AND NOT BOOTSTRAPPING_MODE STREQUAL "HOSTTOOLS")
     message(WARNING "Force setting BOOTSTRAPPING=HOSTTOOLS because Swift parser integration is enabled")
     set(BOOTSTRAPPING_MODE "HOSTTOOLS")
+    if(NOT CMAKE_Swift_COMPILER)
+      message(SEND_ERROR "No Swift compiler found.\n"
+        "Tell CMake where to find the Swift compiler by setting either the "
+        "environment variable \"SWIFTC\" or the CMake cache entry "
+        "CMAKE_Swift_COMPILER to the full path of the compiler, or to the "
+        "compiler name if it is in the PATH")
+    endif()
   endif()
   add_definitions(-DSWIFT_BUILD_SWIFT_SYNTAX)
 endif()