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

[Félix-Antoine Constantin via cfe-commits]

================
@@ -0,0 +1,110 @@
+// RUN: %check_clang_tidy %s readability-redundant-inline-specifier %t
+
+template <typename T> inline T f()
+// CHECK-MESSAGES: :[[@LINE-1]]:23: warning: function 'f' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+// CHECK-FIXES: 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)
+// CHECK-MESSAGES-NOT: :[[@LINE-1]]:1: warning: function 'g' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+{
+    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;
+
+    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;
+    // CHECK-MESSAGES-NOT: :[[@LINE-1]]:5: warning: variable 'C_STATIC_2' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+};
+
+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;
+// CHECK-MESSAGES-NOT: :[[@LINE-1]]:18: warning: variable 'NAMESPACE_STATIC' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+
+inline static int fn0(int i)
+// CHECK-MESSAGES-NOT: :[[@LINE-1]]:1: warning: function 'fn0' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+{
+    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-NOT: :[[@LINE-1]]:5: warning: function 'fn2' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    {
+        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;
+    }
+}
+
+namespace ns
+{
+    inline int fn4(int i)
+    // CHECK-MESSAGES-NOT: :[[@LINE-1]]:5: warning: function 'fn4' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+    {
+        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 = [](){};
+//CHECK-MESSAGES-NOT: :[[@LINE-1]]:1: warning: function 'operator()' has inline specifier but is implicitly inlined [readability-redundant-inline-specifier]
+
----------------
felix642 wrote:

The current implementation does not raise any warnings if the inline keyword is inside a macro since the method `getInlineTokenLocation` is not able to match the location of the inline keyword. 

I'm wondering if we want to ignore those cases with macro since it might be require to remove the keyword in one case but might not apply to another case. From what I can see, most checks seem to ignore macros, should we do the same with this one? 

https://github.com/llvm/llvm-project/pull/73069