[clang-tools-extra] Add clang-tidy check to suggest replacement of conditional statement with std::min/std::max (PR #77816)

[Félix-Antoine Constantin via cfe-commits]

================
@@ -0,0 +1,121 @@
+// RUN: %check_clang_tidy %s readability-use-std-min-max %t
+
+constexpr int myConstexprMin(int a, int b) {
+  return a < b ? a : b;
+}
+
+constexpr int myConstexprMax(int a, int b) {
+  return a > b ? a : b;
+}
+
+int bar(int x, int y) {
+  return x < y ? x : y;
+}
+
+class MyClass {
+public:
+  int member1;
+  int member2;
+};
+
+void foo() {
+  int value1,value2,value3;
+  short value4;
+  MyClass obj;
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  if (value1 < value2)
+    value1 = value2; // CHECK-FIXES: value1 = std::max(value1, value2);
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::min` instead of `<` [readability-use-std-min-max]
+  if (value1 < value2)
+    value2 = value1; // CHECK-FIXES: value2 = std::min(value1, value2);
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::min` instead of `>` [readability-use-std-min-max]
+  if (value2 > value1)
+    value2 = value1; // CHECK-FIXES: value2 = std::min(value2, value1);
+
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::max` instead of `>` [readability-use-std-min-max
+  if (value2 > value1)
+    value1 = value2; // CHECK-FIXES: value1 = std::max(value2, value1);
+
+  // No suggestion needed here
+  if (value1 == value2)
+    value1 = value2;
+  
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  if(value1<value4)
+    value1=value4; // CHECK-FIXES: value1 = std::max(value1, value4);
+  
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::min` instead of `<` [readability-use-std-min-max]
+  if(value1+value2<value3)
+    value3 = value1+value2; // CHECK-FIXES: value3 = std::min(value1+value2, value3);
+  
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  if (value1 < myConstexprMin(value2, value3))
+    value1 = myConstexprMin(value2, value3); // CHECK-FIXES: value1 = std::max(value1, myConstexprMin(value2, value3));
+  
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::min` instead of `>` [readability-use-std-min-max]
+  if (value1 > myConstexprMax(value2, value3))
+    value1 = myConstexprMax(value2, value3); // CHECK-FIXES: value1 = std::min(value1, myConstexprMax(value2, value3));
+  
+  // CHECK-MESSAGES: :[[@LINE+1]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  if (value1 < bar(value2, value3))
----------------
felix642 wrote:

I'm not quite sure about this one. What if bar() has some side-effects ? This will break the code since the method will be called once rather than twice. 

https://github.com/llvm/llvm-project/pull/77816