Add support for ignoring -index-file

Author: vinivendra

include/swift/AST/DiagnosticsDriver.def

@@ -169,8 +169,8 @@ WARNING(warn_ignoring_batch_mode, none,
         "ignoring '-enable-batch-mode' because '%0' was also specified",
         (StringRef))
 
-WARNING(warn_ignoring_wmo, none,
-        "ignoring '-wmo' because '-dump-ast' was also specified", ())
+WARNING(warn_ignoring_single_compile, none,
+        "ignoring '%0' because '-dump-ast' was also specified", (StringRef))
 
 WARNING(warn_ignoring_source_range_dependencies,none,
 "ignoring '-enable-source-range-dependencies' because '%0' was also specified", (StringRef))

lib/Driver/Driver.cpp

@@ -1758,12 +1758,13 @@ Driver::computeCompilerMode(const DerivedArgList &Args,
   const Arg *ArgRequiringSinglePrimaryCompile =
       Args.getLastArg(options::OPT_enable_source_range_dependencies);
 
-  // AST dump doesn't work in WMO. Since it's not common want to dump the AST,
-  // we assume that's the priority and ignore `-wmo`, but we warn the user about
-  // this decision.
-  if (Args.hasArg(options::OPT_whole_module_optimization) &&
+  // AST dump doesn't work with `-wmo` or `-index-file`. Since it's not common
+  // to want to dump the AST, we assume that's the priority and ignore the
+  // conflicting option, but we warn the user about this decision.
+  if (ArgRequiringSingleCompile &&
       Args.hasArg(options::OPT_dump_ast)) {
-    Diags.diagnose(SourceLoc(), diag::warn_ignoring_wmo);
+    Diags.diagnose(SourceLoc(), diag::warn_ignoring_single_compile,
+                   ArgRequiringSingleCompile->getOption().getPrefixedName());
     return OutputInfo::Mode::StandardCompile;
   }