Add support for C unions in Swift.

lldb/packages/Python/lldbsuite/test/lang/swift/clangimporter/union/Makefile

@@ -0,0 +1,4 @@
+SWIFT_SOURCES := main.swift
+SWIFTFLAGS_EXTRAS = -I$(SRCDIR)
+
+include Makefile.rules

lldb/packages/Python/lldbsuite/test/lang/swift/clangimporter/union/TestSwiftCUnion.py

@@ -0,0 +1,19 @@
+import lldb
+from lldbsuite.test.decorators import *
+import lldbsuite.test.lldbtest as lldbtest
+import lldbsuite.test.lldbutil as lldbutil
+import os
+import unittest2
+
+
+class TestSwiftAnyType(lldbtest.TestBase):
+
+    mydir = lldbtest.TestBase.compute_mydir(__file__)
+
+    @swiftTest
+    def test_c_unions(self):
+        self.build()
+        target, process, thread, bkpt = lldbutil.run_to_source_breakpoint(
+            self, 'break here', lldb.SBFileSpec('main.swift'))
+        self.expect("target variable -- i", substrs=['42'])
+        self.expect("target variable -- d", substrs=['23'])

lldb/packages/Python/lldbsuite/test/lang/swift/clangimporter/union/main.swift

@@ -0,0 +1,7 @@
+import U
+
+func use<T>(_ t : T) {}
+
+let i = IntDoubleUnion(i: 42)
+let d = IntDoubleUnion(d: 23)
+use((i, d)) // break here

lldb/packages/Python/lldbsuite/test/lang/swift/clangimporter/union/module.modulemap

@@ -0,0 +1 @@
+module U { header "union.h" }

lldb/packages/Python/lldbsuite/test/lang/swift/clangimporter/union/union.h

@@ -0,0 +1,4 @@
+union IntDoubleUnion {
+  int i;
+  double d;
+};

lldb/source/Symbol/SwiftASTContext.cpp

@@ -6648,6 +6648,16 @@ uint32_t SwiftASTContext::GetNumFields(void *type) {
   case swift::TypeKind::BoundGenericClass:
   case swift::TypeKind::BoundGenericStruct: {
     auto nominal = swift_can_type->getAnyNominal();
+    // Imported unions don't have stored properties.
+    if (auto *ntd =
+            llvm::dyn_cast_or_null<swift::NominalTypeDecl>(nominal->getDecl()))
+      if (auto *rd = llvm::dyn_cast_or_null<clang::RecordDecl>(ntd->getClangDecl()))
+        if (rd->isUnion()) {
+          swift::DeclRange ms = ntd->getMembers();
+          return std::count_if(ms.begin(), ms.end(), [](swift::Decl *D) {
+            return llvm::isa<swift::VarDecl>(D);
+          });
+        }
     return GetStoredProperties(nominal).size();
   }
 
@@ -7295,6 +7305,38 @@ CompilerType SwiftASTContext::GetChildCompilerTypeAtIndex(
   case swift::TypeKind::Struct:
   case swift::TypeKind::BoundGenericStruct: {
     auto nominal = swift_can_type->getAnyNominal();
+
+    // Imported unions don't have stored properties, iterate over the
+    // VarDecls instead.
+    if (auto *ntd =
+            llvm::dyn_cast_or_null<swift::NominalTypeDecl>(nominal->getDecl()))
+      if (auto *rd = llvm::dyn_cast_or_null<clang::RecordDecl>(ntd->getClangDecl()))
+        if (rd->isUnion()) {
+          unsigned count = 0;
+          for (swift::Decl *D : ntd->getMembers()) {
+            auto *VD = llvm::dyn_cast_or_null<swift::VarDecl>(D);
+            if (!VD)
+              continue;
+            if (count++ < idx)
+              continue;
+
+            swift::Type child_swift_type = VD->getType();
+
+            CompilerType child_type =
+                ToCompilerType(VD->getType().getPointer());
+            child_name = VD->getNameStr();
+            if (!get_type_size(child_byte_size, child_type))
+              return {};
+            child_is_base_class = false;
+            child_is_deref_of_parent = false;
+            child_byte_offset = 0;
+            child_bitfield_bit_size = 0;
+            child_bitfield_bit_offset = 0;
+            return child_type;
+          }
+          return {};
+        }
+
     auto stored_properties = GetStoredProperties(nominal);
     if (idx >= stored_properties.size())
       break;