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

[Félix-Antoine Constantin via llvm-commits]

================
@@ -0,0 +1,175 @@
+// RUN: %check_clang_tidy %s readability-use-std-min-max %t
+
+#define MY_MACRO_MIN(a, b) ((a) < (b) ? (a) : (b))
+
+constexpr int myConstexprMin(int a, int b) {
+  return a < b ? a : b;
+}
+
+constexpr int myConstexprMax(int a, int b) {
+  return a > b ? a : b;
+}
+
+#define MY_IF_MACRO(condition, statement) \
+  if (condition) {                        \
+    statement                             \
+  }
+
+class MyClass {
+public:
+  int member1;
+  int member2;
+};
+
+void foo() {
+  int value1,value2,value3;
+  short value4;
+  MyClass obj;
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: value1 = std::max(value1, value2);
+  if (value1 < value2)
+    value1 = value2; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: value2 = std::min(value1, value2);
+  if (value1 < value2)
+    value2 = value1; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `>` [readability-use-std-min-max]
+  // CHECK-FIXES: value2 = std::min(value2, value1);
+  if (value2 > value1)
+    value2 = value1; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `>` [readability-use-std-min-max
+  // CHECK-FIXES: value1 = std::max(value2, value1);
+  if (value2 > value1)
+    value1 = value2; 
+
+  // No suggestion needed here
+  if (value1 == value2)
+    value1 = value2;
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: value1 = std::max<int>(value1, value4);
+  if(value1<value4)
+    value1=value4; 
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: value3 = std::min(value1+value2, value3);
+  if(value1+value2<value3)
+    value3 = value1+value2; 
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: value1 = std::max(value1, myConstexprMin(value2, value3));
+  if (value1 < myConstexprMin(value2, value3))
+    value1 = myConstexprMin(value2, value3); 
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `>` [readability-use-std-min-max]
+  // CHECK-FIXES: value1 = std::min(value1, myConstexprMax(value2, value3));
+  if (value1 > myConstexprMax(value2, value3))
+    value1 = myConstexprMax(value2, value3); 
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `<=` [readability-use-std-min-max]
+  // CHECK-FIXES: value2 = std::min(value1, value2);
+  if (value1 <= value2)
+    value2 = value1; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `<=` [readability-use-std-min-max]
+  // CHECK-FIXES: value1 = std::max(value1, value2);
+  if (value1 <= value2)
+    value1 = value2; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `>=` [readability-use-std-min-max]
+  // CHECK-FIXES: value1 = std::max(value2, value1);
+  if (value2 >= value1)
+    value1 = value2; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `>=` [readability-use-std-min-max]
+  // CHECK-FIXES: value2 = std::min(value2, value1);
+  if (value2 >= value1)
+    value2 = value1; 
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: obj.member1 = std::max(obj.member1, obj.member2);
+  if (obj.member1 < obj.member2)
+    obj.member1 = obj.member2; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: obj.member2 = std::min(obj.member1, obj.member2);
+  if (obj.member1 < obj.member2)
+    obj.member2 = obj.member1; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `>` [readability-use-std-min-max]
+  // CHECK-FIXES: obj.member2 = std::min(obj.member2, obj.member1);
+  if (obj.member2 > obj.member1)
+    obj.member2 = obj.member1; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `>` [readability-use-std-min-max]
+  // CHECK-FIXES: obj.member1 = std::max(obj.member2, obj.member1);
+  if (obj.member2 > obj.member1)
+    obj.member1 = obj.member2; 
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: obj.member1 = std::max<int>(obj.member1, value4);
+  if (obj.member1 < value4)
+    obj.member1 = value4; 
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: value3 = std::min(obj.member1 + value2, value3);
+  if (obj.member1 + value2 < value3)
+    value3 = obj.member1 + value2; 
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `<=` [readability-use-std-min-max]
+  // CHECK-FIXES: obj.member2 = std::min(value1, obj.member2);
+  if (value1 <= obj.member2)
+    obj.member2 = value1; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `<=` [readability-use-std-min-max]
+  // CHECK-FIXES: value1 = std::max(value1, obj.member2);
+  if (value1 <= obj.member2)
+    value1 = obj.member2; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `>=` [readability-use-std-min-max]
+  // CHECK-FIXES: value1 = std::max(obj.member2, value1);
+  if (obj.member2 >= value1)
+    value1 = obj.member2; 
+
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `>=` [readability-use-std-min-max]
+  // CHECK-FIXES: obj.member2 = std::min(obj.member2, value1);
+  if (obj.member2 >= value1)
+    obj.member2 = value1; 
+  
+  // No suggestion needed here
+  if (MY_MACRO_MIN(value1, value2) < value3)
+    value3 = MY_MACRO_MIN(value1, value2); 
+  
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::max` instead of `<` [readability-use-std-min-max]
+  // CHECK-FIXES: value4 = std::max<short>(value4, value2);
+  if (value4 < value2){
+    value4 = value2; 
+  }
+
+  // No suggestion needed here
+  if(value1 < value2)
+    value2 = value1;
+  else
+    value2 = value3;
+  
+  // No suggestion needed here
+  if(value1<value2){
+    value2 = value1; 
+  }
+  else{
+    value2 = value3;  
+  }
+
+  // No suggestion needed here
+  if(value1<value2){
+    value2 = value1; 
+    int res = value1 + value2;
+  }
+
+  // No suggestion needed here
+  MY_IF_MACRO(value1 < value2, value1 = value2;)
----------------
felix642 wrote:

I apologies for my iterative feedback, but I just realized that we're missing a test that might not be working properly. Could you please add the following test and validate that it works properly? 

```
int var1, var2;
if(var1 < var2)
{
    var1 = var2;
}
else if(var1 > var2)
{
    var2 = var1;
}
```


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