[sil] As a fallback, if a parsed SILFunction does not have a DeclContext, set its parent SwiftModule to be the SwiftModule of its SILModule.

This ensures that we can successfully perform protocol conformance checks when
testing SIL files.

Author: gottesmm

lib/SIL/Parser/SILParserFunctionBuilder.h

@@ -31,6 +31,15 @@ class LLVM_LIBRARY_VISIBILITY SILParserFunctionBuilder {
         IsNotTransparent, IsNotSerialized, IsNotDynamic, IsNotDistributed,
         IsNotRuntimeAccessible);
     result->setDebugScope(new (builder.mod) SILDebugScope(loc, result));
+
+    // If we did not have a declcontext set, as a fallback set the parent module
+    // of our SILFunction to the parent module of our SILModule.
+    //
+    // DISCUSSION: This ensures that we can perform protocol conformance checks.
+    if (!result->getDeclContext()) {
+      result->setParentModule(result->getModule().getSwiftModule());
+    }
+
     return result;
   }
 };