[clang-tidy] Added new check to detect redundant inline keyword (#73069)

This checks find usages of the inline keywork where it is already
implicitly defined by the compiler and suggests it's removal.

Fixes #72397

Author: felix642

clang-tools-extra/clang-tidy/readability/CMakeLists.txt

@@ -22,6 +22,7 @@ add_clang_library(clangTidyReadabilityModule
   IdentifierLengthCheck.cpp
   IdentifierNamingCheck.cpp
   ImplicitBoolConversionCheck.cpp
+  RedundantInlineSpecifierCheck.cpp
   InconsistentDeclarationParameterNameCheck.cpp
   IsolateDeclarationCheck.cpp
   MagicNumbersCheck.cpp

clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp

@@ -42,6 +42,7 @@
 #include "RedundantControlFlowCheck.h"
 #include "RedundantDeclarationCheck.h"
 #include "RedundantFunctionPtrDereferenceCheck.h"
+#include "RedundantInlineSpecifierCheck.h"
 #include "RedundantMemberInitCheck.h"
 #include "RedundantPreprocessorCheck.h"
 #include "RedundantSmartptrGetCheck.h"
@@ -100,6 +101,8 @@ class ReadabilityModule : public ClangTidyModule {
         "readability-identifier-naming");
     CheckFactories.registerCheck<ImplicitBoolConversionCheck>(
         "readability-implicit-bool-conversion");
+    CheckFactories.registerCheck<RedundantInlineSpecifierCheck>(
+        "readability-redundant-inline-specifier");
     CheckFactories.registerCheck<InconsistentDeclarationParameterNameCheck>(
         "readability-inconsistent-declaration-parameter-name");
     CheckFactories.registerCheck<IsolateDeclarationCheck>(

clang-tools-extra/clang-tidy/readability/RedundantInlineSpecifierCheck.cpp

@@ -0,0 +1,132 @@
+//===--- RedundantInlineSpecifierCheck.cpp - clang-tidy--------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "RedundantInlineSpecifierCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/AST/DeclTemplate.h"
+#include "clang/AST/ExprCXX.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Lex/Token.h"
+
+#include "../utils/LexerUtils.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+namespace {
+AST_POLYMORPHIC_MATCHER(isInlineSpecified,
+                        AST_POLYMORPHIC_SUPPORTED_TYPES(FunctionDecl,
+                                                        VarDecl)) {
+  if (const auto *FD = dyn_cast<FunctionDecl>(&Node))
+    return FD->isInlineSpecified();
+  if (const auto *VD = dyn_cast<VarDecl>(&Node))
+    return VD->isInlineSpecified();
+  llvm_unreachable("Not a valid polymorphic type");
+}
+
+AST_POLYMORPHIC_MATCHER_P(isInternalLinkage,
+                          AST_POLYMORPHIC_SUPPORTED_TYPES(FunctionDecl,
+                                                          VarDecl),
+                          bool, strictMode) {
+  if (!strictMode)
+    return false;
+  if (const auto *FD = dyn_cast<FunctionDecl>(&Node))
+    return FD->getStorageClass() == SC_Static || FD->isInAnonymousNamespace();
+  if (const auto *VD = dyn_cast<VarDecl>(&Node))
+    return VD->isInAnonymousNamespace();
+  llvm_unreachable("Not a valid polymorphic type");
+}
+} // namespace
+
+static SourceLocation getInlineTokenLocation(SourceRange RangeLocation,
+                                             const SourceManager &Sources,
+                                             const LangOptions &LangOpts) {
+  SourceLocation Loc = RangeLocation.getBegin();
+  if (Loc.isMacroID())
+    return {};
+
+  Token FirstToken;
+  Lexer::getRawToken(Loc, FirstToken, Sources, LangOpts, true);
+  std::optional<Token> CurrentToken = FirstToken;
+  while (CurrentToken && CurrentToken->getLocation() < RangeLocation.getEnd() &&
+         CurrentToken->isNot(tok::eof)) {
+    if (CurrentToken->is(tok::raw_identifier) &&
+        CurrentToken->getRawIdentifier() == "inline")
+      return CurrentToken->getLocation();
+
+    CurrentToken =
+        Lexer::findNextToken(CurrentToken->getLocation(), Sources, LangOpts);
+  }
+  return {};
+}
+
+void RedundantInlineSpecifierCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      functionDecl(isInlineSpecified(),
+                   anyOf(isConstexpr(), isDeleted(), isDefaulted(),
+                         isInternalLinkage(StrictMode),
+                         allOf(isDefinition(), hasAncestor(recordDecl()))))
+          .bind("fun_decl"),
+      this);
+
+  if (StrictMode)
+    Finder->addMatcher(
+        functionTemplateDecl(
+            has(functionDecl(allOf(isInlineSpecified(), isDefinition()))))
+            .bind("templ_decl"),
+        this);
+
+  if (getLangOpts().CPlusPlus17) {
+    Finder->addMatcher(
+        varDecl(isInlineSpecified(),
+                anyOf(isInternalLinkage(StrictMode),
+                      allOf(isConstexpr(), hasAncestor(recordDecl()))))
+            .bind("var_decl"),
+        this);
+  }
+}
+
+template <typename T>
+void RedundantInlineSpecifierCheck::handleMatchedDecl(
+    const T *MatchedDecl, const SourceManager &Sources,
+    const MatchFinder::MatchResult &Result, StringRef Message) {
+  SourceLocation Loc = getInlineTokenLocation(
+      MatchedDecl->getSourceRange(), Sources, Result.Context->getLangOpts());
+  if (Loc.isValid())
+    diag(Loc, Message) << MatchedDecl << FixItHint::CreateRemoval(Loc);
+}
+
+void RedundantInlineSpecifierCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const SourceManager &Sources = *Result.SourceManager;
+
+  if (const auto *MatchedDecl =
+          Result.Nodes.getNodeAs<FunctionDecl>("fun_decl")) {
+    handleMatchedDecl(
+        MatchedDecl, Sources, Result,
+        "function %0 has inline specifier but is implicitly inlined");
+  } else if (const auto *MatchedDecl =
+                 Result.Nodes.getNodeAs<VarDecl>("var_decl")) {
+    handleMatchedDecl(
+        MatchedDecl, Sources, Result,
+        "variable %0 has inline specifier but is implicitly inlined");
+  } else if (const auto *MatchedDecl =
+                 Result.Nodes.getNodeAs<FunctionTemplateDecl>("templ_decl")) {
+    handleMatchedDecl(
+        MatchedDecl, Sources, Result,
+        "function %0 has inline specifier but is implicitly inlined");
+  }
+}
+
+} // namespace clang::tidy::readability

clang-tools-extra/clang-tidy/readability/RedundantInlineSpecifierCheck.h

@@ -0,0 +1,42 @@
+//===--- RedundantInlineSpecifierCheck.h - clang-tidy ------------*-C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTINLINESPECIFIERCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTINLINESPECIFIERCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::readability {
+
+/// Detects redundant ``inline`` specifiers on function and variable
+/// declarations.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/readability/redundant-inline-specifier.html
+class RedundantInlineSpecifierCheck : public ClangTidyCheck {
+public:
+  RedundantInlineSpecifierCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context),
+        StrictMode(Options.getLocalOrGlobal("StrictMode", false)) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+  std::optional<TraversalKind> getCheckTraversalKind() const override {
+    return TK_IgnoreUnlessSpelledInSource;
+  }
+
+private:
+  template <typename T>
+  void handleMatchedDecl(const T *MatchedDecl, const SourceManager &Sources,
+                         const ast_matchers::MatchFinder::MatchResult &Result,
+                         StringRef Message);
+  const bool StrictMode;
+};
+
+} // namespace clang::tidy::readability
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANTINLINESPECIFIERCHECK_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -240,6 +240,11 @@ New checks
 
   Detects explicit type casting operations that involve the same source and
   destination types, and subsequently recommend their removal.
+  
+- New :doc:`readability-redundant-inline-specifier
+  <clang-tidy/checks/readability/redundant-inline-specifier>` check.
+
+  Detects redundant ``inline`` specifiers on function and variable declarations.
 
 - New :doc:`readability-reference-to-constructed-temporary
   <clang-tidy/checks/readability/reference-to-constructed-temporary>` check.

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -354,6 +354,7 @@ Clang-Tidy Checks
    :doc:`readability-identifier-length <readability/identifier-length>`,
    :doc:`readability-identifier-naming <readability/identifier-naming>`, "Yes"
    :doc:`readability-implicit-bool-conversion <readability/implicit-bool-conversion>`, "Yes"
+   :doc:`readability-redundant-inline-specifier <readability/redundant-inline-specifier>`, "Yes"
    :doc:`readability-inconsistent-declaration-parameter-name <readability/inconsistent-declaration-parameter-name>`, "Yes"
    :doc:`readability-isolate-declaration <readability/isolate-declaration>`, "Yes"
    :doc:`readability-magic-numbers <readability/magic-numbers>`,

clang-tools-extra/docs/clang-tidy/checks/readability/redundant-inline-specifier.rst

@@ -0,0 +1,32 @@
+.. title:: clang-tidy - readability-redundant-inline-specifier
+
+readability-redundant-inline-specifier
+======================================
+
+Detects redundant ``inline`` specifiers on function and variable declarations.
+
+Examples:
+
+.. code-block:: c++
+
+   constexpr inline void f() {}
+
+In the example above the keyword ``inline`` is redundant since constexpr
+functions are implicitly inlined
+
+.. code-block:: c++
+   
+   class MyClass {
+       inline void myMethod() {}
+   };
+
+In the example above the keyword ``inline`` is redundant since member functions
+defined entirely inside a class/struct/union definition are implicitly inlined.
+
+Options
+-------
+
+.. option:: StrictMode
+
+   If set to `true`, the check will also flag functions and variables that
+   already have internal linkage as redundant.

clang-tools-extra/test/clang-tidy/checkers/readability/redundant-inline-specifier.cpp

@@ -0,0 +1,137 @@
+// RUN: %check_clang_tidy -std=c++17 %s readability-redundant-inline-specifier %t
+// RUN: %check_clang_tidy -std=c++17 -check-suffixes=,STRICT %s readability-redundant-inline-specifier %t -- -config="{CheckOptions: {readability-redundant-inline-specifier.StrictMode: 'true'}}"
+
+template <typename T> inline T f()
+// CHECK-MESSAGES-STRICT: :[[@LINE-1]]:23: warning: function 'f' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+// CHECK-FIXES-STRICT: template <typename T> T f()
+{
+    return T{};
+}
+
+template <> inline double f<double>() = delete;
+// CHECK-MESSAGES: :[[@LINE-1]]:13: warning: function 'f<double>' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+// CHECK-FIXES: template <> double f<double>() = delete;
+
+inline int g(float a)
+{
+    return static_cast<int>(a - 5.F);
+}
+
+inline int g(double) = delete;
+// CHECK-MESSAGES: :[[@LINE-1]]:1: warning: function 'g' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+// CHECK-FIXES: int g(double) = delete;
+
+class C
+{
+  public:
+    inline C& operator=(const C&) = delete;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'operator=' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES: C& operator=(const C&) = delete;
+
+    inline C(const C&) = default;
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'C' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES: C(const C&) = default;
+
+    constexpr inline C& operator=(int a);
+    // CHECK-MESSAGES: :[[@LINE-1]]:15: warning: function 'operator=' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES: constexpr C& operator=(int a);
+
+    inline C() {}
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'C' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES: C() {}
+
+    constexpr inline C(int);
+    // CHECK-MESSAGES: :[[@LINE-1]]:15: warning: function 'C' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES: constexpr C(int);
+
+    inline int Get42() const { return 42; }
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'Get42' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES: int Get42() const { return 42; }
+
+    static inline constexpr int C_STATIC = 42;
+    // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: variable 'C_STATIC' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES: static constexpr int C_STATIC = 42;
+
+    static constexpr int C_STATIC_2 = 42;
+};
+
+constexpr inline int Get42() { return 42; }
+// CHECK-MESSAGES: :[[@LINE-1]]:11: warning: function 'Get42' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+// CHECK-FIXES: constexpr int Get42() { return 42; }
+
+
+static constexpr inline int NAMESPACE_STATIC = 42;
+
+inline static int fn0(int i)
+// CHECK-MESSAGES-STRICT: :[[@LINE-1]]:1: warning: function 'fn0' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+// CHECK-FIXES-STRICT: static int fn0(int i)
+{
+    return i - 1;
+}
+
+static constexpr inline int fn1(int i)
+// CHECK-MESSAGES: :[[@LINE-1]]:18: warning: function 'fn1' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+// CHECK-FIXES: static constexpr int fn1(int i)
+{
+    return i - 1;
+}
+
+namespace
+{
+    inline int fn2(int i)
+    // CHECK-MESSAGES-STRICT: :[[@LINE-1]]:5: warning: function 'fn2' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES-STRICT: int fn2(int i)
+    {
+        return i - 1;
+    }
+
+    inline constexpr int fn3(int i)
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'fn3' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES: constexpr int fn3(int i)
+    {
+        return i - 1;
+    }
+
+    inline constexpr int MY_CONSTEXPR_VAR = 42;
+    // CHECK-MESSAGES-STRICT: :[[@LINE-1]]:5: warning: variable 'MY_CONSTEXPR_VAR' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES-STRICT: constexpr int MY_CONSTEXPR_VAR = 42;
+}
+
+namespace ns
+{
+    inline int fn4(int i)
+    {
+        return i - 1;
+    }
+
+    inline constexpr int fn5(int i)
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: function 'fn5' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    // CHECK-FIXES: constexpr int fn5(int i)
+    {
+        return i - 1;
+    }
+}
+
+auto fn6 = [](){};
+
+template <typename T> inline T fn7();
+
+template <typename T> T fn7()
+{
+    return T{};
+}
+
+template <typename T>  T fn8();
+
+template <typename T> inline T fn8()
+// CHECK-MESSAGES-STRICT: :[[@LINE-1]]:23: warning: function 'fn8' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+// CHECK-FIXES-STRICT: template <typename T> T fn8()
+{
+    return T{};
+}
+
+#define INLINE_MACRO() inline void fn9() { }
+INLINE_MACRO()
+
+#define INLINE_KW inline
+INLINE_KW void fn10() { }