style(clang-tidy): fix issues it found in CI

Curiously, the changed includes seem to allow `clang-tidy` to see issues
that it previously didn't see. This commit fixes them.

Signed-off-by: Ingo Müller <ingomueller@google.com>

Author: ingomueller-net

include/substrait/common/Exceptions.h

@@ -35,7 +35,7 @@ inline constexpr const char* kNotImplemented = "NOT_IMPLEMENTED";
 
 class SubstraitException : public std::exception {
  public:
-  enum class Type {
+  enum class Type : int8_t {
     // Errors where the root cause of the problem is either because of bad input
     // or an unsupported pattern of use are classified with USER. Examples
     // of errors in this category include syntax errors, unavailable names or

include/substrait/common/Io.h

@@ -13,7 +13,7 @@ namespace io::substrait {
 /*
  * \brief The four different ways plans can be represented on disk.
  */
-enum class PlanFileFormat {
+enum class PlanFileFormat : int8_t {
   kBinary = 0,
   kJson = 1,
   kProtoText = 2,

include/substrait/expression/DecimalLiteral.h

@@ -7,7 +7,7 @@
 #include <utility>
 
 namespace substrait::proto {
-class Expression_Literal_Decimal;
+class Expression_Literal_Decimal; // NOLINT
 }
 
 namespace io::substrait::expression {

include/substrait/function/Function.h

@@ -39,7 +39,7 @@ struct FunctionArgument {
 using FunctionArgumentPtr = std::shared_ptr<FunctionArgument>;
 
 struct EnumArgument : public FunctionArgument {
-  bool required{};
+  bool required;
 
   [[nodiscard]] bool isRequired() const override {
     return required;

include/substrait/function/FunctionLookup.h

@@ -25,7 +25,7 @@ class FunctionLookup {
  protected:
   [[nodiscard]] virtual FunctionImplMap getFunctionImpls() const = 0;
 
-  ExtensionPtr extension_{};
+  ExtensionPtr extension_;
 };
 
 using FunctionLookupPtr = std::shared_ptr<const FunctionLookup>;

src/substrait/textplan/SymbolTable.h

@@ -19,7 +19,7 @@
 
 namespace io::substrait::textplan {
 
-enum class SymbolType {
+enum class SymbolType : int8_t {
   kExtensionSpace = 0,
   kFunction = 1,
   kPlanRelation = 2,
@@ -36,7 +36,7 @@ enum class SymbolType {
   kUnknown = -1,
 };
 
-enum class RelationType {
+enum class RelationType : int8_t {
   // Logical
   kUnknown = 0,
   kRead = 1,
@@ -64,12 +64,12 @@ enum class RelationType {
   kExtensionMulti = 102,
 };
 
-enum class RelationDetailType {
+enum class RelationDetailType : int8_t {
   kUnknown = 0,
   kExpression = 1,
 };
 
-enum class SourceType {
+enum class SourceType : int8_t {
   kUnknown = 0,
   kLocalFiles = 1,
   kNamedTable = 2,
@@ -81,7 +81,7 @@ const std::string& symbolTypeName(SymbolType type);
 
 struct SymbolInfo {
   std::string name;
-  std::string alias{}; // If present, use this instead of name.
+  std::string alias; // If present, use this instead of name.
   const SymbolInfo* schema{nullptr}; // The related schema symbol if present.
   Location sourceLocation;
   Location permanentLocation{Location::kUnknownLocation};

src/substrait/textplan/parser/SubstraitPlanRelationVisitor.h

@@ -19,9 +19,9 @@
 
 namespace substrait::proto {
 class Expression;
-class Expression_Literal;
-class Expression_Literal_Map_KeyValue;
-class Type_Struct;
+class Expression_Literal; // NOLINT
+class Expression_Literal_Map_KeyValue; // NOLINT
+class Type_Struct; // NOLINT
 } // namespace substrait::proto
 
 namespace io::substrait::textplan {

src/substrait/textplan/parser/SubstraitPlanSubqueryRelationVisitor.h

@@ -19,9 +19,9 @@
 
 namespace substrait::proto {
 class Expression;
-class Expression_Literal;
-class Expression_Literal_Map_KeyValue;
-class Type_Struct;
+class Expression_Literal; // NOLINT
+class Expression_Literal_Map_KeyValue; // NOLINT
+class Type_Struct; // NOLINT
 } // namespace substrait::proto
 
 namespace io::substrait::textplan {

src/substrait/textplan/tests/RoundtripTest.cpp

@@ -59,7 +59,7 @@ class RoundTripBinaryToTextFixture
 
 std::vector<std::string> getTestCases() {
   const std::filesystem::path currPath = std::filesystem::current_path();
-  std::vector<std::string> filenames{};
+  std::vector<std::string> filenames;
   std::filesystem::path testDataPath = currPath;
   testDataPath.append("data");
   for (auto const& dirEntry :