[lldb] Introduce precise Fallback SwiftASTContexts.

When we switched to precise compiler invocations, we still kept the
per-module fallback SwiftASTContext. This can be a problem when also
using explicit modules, because explicit module imports only work with
precise compiler invocations. This patch changes
TypeSystemSwiftTyperef to pass its SymbolContext when creating its
fallback SwiftASTContext. This basically turns on precise compiler
invocationsfor fallback contexts. The price is more compiler
instances, but this is only way to make them work reliably with
explicit modules.

rdar://137087616

Author: adrian-prantl

lldb/source/Plugins/Language/Swift/SwiftUnsafeTypes.cpp

@@ -203,8 +203,11 @@ SwiftUnsafeRawBufferPointer::SwiftUnsafeRawBufferPointer(ValueObject &valobj)
 }
 
 lldb::ChildCacheState SwiftUnsafeRawBufferPointer::Update() {
-  if (!m_valobj.GetNumChildren())
+  auto num_or_error = m_valobj.GetNumChildren();
+  if (!num_or_error) {
+    llvm::consumeError(num_or_error.takeError());
     return ChildCacheState::eRefetch;
+  }
 
   // Here is the layout of Swift's UnsafeRaw[Mutable]BufferPointer.
   // It's a view of the raw bytes of the pointee object. Each byte is viewed as

lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.cpp

@@ -207,7 +207,7 @@ class SwiftASTContext : public TypeSystemSwift {
   /// context.
   static lldb::TypeSystemSP
   CreateInstance(const SymbolContext &sc,
-                 TypeSystemSwiftTypeRefForExpressions &typeref_typesystem,
+                 TypeSystemSwiftTypeRef &typeref_typesystem,
                  const char *extra_options = nullptr);
 
   static void EnumerateSupportedLanguages(

lldb/source/Plugins/TypeSystem/Swift/SwiftASTContext.h

@@ -1839,8 +1839,7 @@ TypeSystemSwiftTypeRef::GetSwiftASTContext(const SymbolContext &sc) const {
 
   // Create a new SwiftASTContextForExpressions.
   TypeSystemSP ts = SwiftASTContext::CreateInstance(
-      LanguageType::eLanguageTypeSwift, *m_module,
-      *const_cast<TypeSystemSwiftTypeRef *>(this));
+      sc, *const_cast<TypeSystemSwiftTypeRef *>(this));
   m_swift_ast_context_map.insert({key, ts});
 
   auto *swift_ast_context = llvm::dyn_cast_or_null<SwiftASTContext>(ts.get());

lldb/source/Plugins/TypeSystem/Swift/TypeSystemSwiftTypeRef.cpp

@@ -49,7 +49,7 @@ def testSwiftDebugMacros(self):
 #       CHECK: SwiftASTContextForExpressions{{.*}}-DSPACE
 #       CHECK-NOT: {{ SPACE}}
 #       CHECK: SwiftASTContextForExpressions{{.*}}-UNDEBUG
-#       CHECK: SwiftASTContextForModule("libDylib{{.*}}-DDEBUG=1
-#       CHECK: SwiftASTContextForModule("libDylib{{.*}}-DSPACE
+#       CHECK: SwiftASTContext(module: "Dylib{{.*}}-DDEBUG=1
+#       CHECK: SwiftASTContext(module: "Dylib{{.*}}-DSPACE
 #       CHECK-NOT: {{ SPACE}}
-#       CHECK: SwiftASTContextForModule("libDylib{{.*}}-UNDEBUG
+#       CHECK: SwiftASTContext(module: "Dylib{{.*}}-UNDEBUG

lldb/test/API/lang/swift/clangimporter/config_macros/TestSwiftDedupMacros.py

@@ -91,5 +91,5 @@ def test_swift_precise_compiler_invocation_triple(self):
         self.filecheck(
             f'platform shell cat "{log}"', __file__, "-check-prefix=CHECK-PRECISE"
         )
-#       CHECK-PRECISE: SwiftASTContextForExpressions(module: "NewerTarget", cu: "NewerTarget.swift")::CreateInstance() -- Fully specified target triple {{.*}}-apple-macosx11.1.0
+#       CHECK-PRECISE: SwiftASTContextForExpressions(module: "NewerTarget", cu: "NewerTarget.swift")::CreateInstance() -- Fully specified triple {{.*}}-apple-macosx11.1.0
 #       CHECK-PRECISE: SwiftASTContextForExpressions(module: "NewerTarget", cu: "NewerTarget.swift")::SetTriple("{{.*}}-apple-macosx11.1.0")

lldb/test/API/lang/swift/deployment_target/TestSwiftDeploymentTarget.py

@@ -26,5 +26,6 @@ def test(self):
         process = target.LaunchSimple(None, None, self.get_process_working_directory())
         self.expect("expression 1")
         self.filecheck('platform shell cat "%s"' % types_log, __file__)
-        # CHECK: {{SwiftASTContextForExpressions.*Preferring module triple .*-apple-macos.[0-9.]+ over target triple .*-apple-macos-unknown.}}
+        # CHECK: {{SwiftASTContextForExpressions.*Module triple: ".*-apple-macos.[0-9.]+"}}
+        # CHECK: {{SwiftASTContextForExpressions.*Target triple: ".*-apple-macos-unknown"}}
         # CHECK: {{SwiftASTContextForExpressions.*setting to ".*-apple-macos.[0-9.]+"}}