[clang][CIR] Fix various warnings. NFC

- Fix various warnings including '-Wparentheses', '-Wunused-variable',
  and '-Wreturn-type'.

Author: darkbuck

clang/include/clang/CIR/Dialect/IR/CIRTypesDetails.h

@@ -54,7 +54,7 @@ struct RecordTypeStorage : public mlir::TypeStorage {
                     RecordType::RecordKind kind)
       : members(members), name(name), incomplete(incomplete), packed(packed),
         padded(padded), kind(kind) {
-    assert(name || !incomplete && "Incomplete records must have a name");
+    assert((name || !incomplete) && "Incomplete records must have a name");
   }
 
   KeyTy getAsKey() const {

clang/lib/CIR/CodeGen/CIRGenBuilder.h

@@ -63,6 +63,7 @@ class CIRGenBuilderTy : public cir::CIRBaseBuilderTy {
     case clang::TagTypeKind::Enum:
       llvm_unreachable("enums are not records");
     }
+    llvm_unreachable("Unsupported record kind");
   }
 
   /// Get an incomplete CIR struct type. If we have a complete record

clang/lib/CIR/CodeGen/CIRGenTypes.cpp

@@ -153,7 +153,7 @@ isSafeToConvert(const RecordDecl *rd, CIRGenTypes &cgt,
   // out, don't do it.  This includes virtual base classes which get laid out
   // when a class is translated, even though they aren't embedded by-value into
   // the class.
-  if (const CXXRecordDecl *crd = dyn_cast<CXXRecordDecl>(rd)) {
+  if (isa<CXXRecordDecl>(rd)) {
     assert(!cir::MissingFeatures::cxxSupport());
     cgt.getCGModule().errorNYI(rd->getSourceRange(),
                                "isSafeToConvert: CXXRecordDecl");
@@ -237,7 +237,7 @@ mlir::Type CIRGenTypes::convertRecordDeclType(const clang::RecordDecl *rd) {
   assert(insertResult && "isSafeToCovert() should have caught this.");
 
   // Force conversion of non-virtual base classes recursively.
-  if (const auto *cxxRecordDecl = dyn_cast<CXXRecordDecl>(rd)) {
+  if (isa<CXXRecordDecl>(rd)) {
     cgm.errorNYI(rd->getSourceRange(), "CXXRecordDecl");
   }