[clang] [clang-tools-extra] [llvm] 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 +1,129 @@
+//===--- UseStdMinMaxCheck.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 "UseStdMinMaxCheck.h"
+#include "../utils/ASTUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Preprocessor.h"
+#include <optional>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+UseStdMinMaxCheck::UseStdMinMaxCheck(StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      IncludeInserter(Options.getLocalOrGlobal("IncludeStyle",
+                                               utils::IncludeSorter::IS_LLVM),
+                      areDiagsSelfContained()) {}
+
+void UseStdMinMaxCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "IncludeStyle", IncludeInserter.getStyle());
+  Options.store(Opts, "AlgorithmHeader",
+                Options.get("AlgorithmHeader", "<algorithm>"));
+}
+
+void UseStdMinMaxCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      ifStmt(
+          hasCondition(binaryOperator(hasAnyOperatorName("<", ">", "<=", ">="),
+                                      hasLHS(expr().bind("CondLhs")),
+                                      hasRHS(expr().bind("CondRhs")))),
+          hasThen(anyOf(stmt(binaryOperator(hasOperatorName("="),
+                                            hasLHS(expr().bind("AssignLhs")),
+                                            hasRHS(expr().bind("AssignRhs")))),
+                        compoundStmt(has(binaryOperator(
+                                         hasOperatorName("="),
+                                         hasLHS(expr().bind("AssignLhs")),
+                                         hasRHS(expr().bind("AssignRhs")))))
+                            .bind("compound"))))
+          .bind("if"),
+      this);
+}
+
+void UseStdMinMaxCheck::registerPPCallbacks(const SourceManager &SM,
+                                            Preprocessor *PP,
+                                            Preprocessor *ModuleExpanderPP) {
+  IncludeInserter.registerPreprocessor(PP);
+}
+
+void UseStdMinMaxCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *CondLhs = Result.Nodes.getNodeAs<Expr>("CondLhs");
+  const auto *CondRhs = Result.Nodes.getNodeAs<Expr>("CondRhs");
+  const auto *AssignLhs = Result.Nodes.getNodeAs<Expr>("AssignLhs");
+  const auto *AssignRhs = Result.Nodes.getNodeAs<Expr>("AssignRhs");
+  const auto *If = Result.Nodes.getNodeAs<IfStmt>("if");
+  const auto *Compound = Result.Nodes.getNodeAs<CompoundStmt>("compound");
+  const auto &Context = *Result.Context;
+  const auto &LO = Context.getLangOpts();
+  const SourceManager &Source = Context.getSourceManager();
+
+  const auto *BinaryOp = dyn_cast<BinaryOperator>(If->getCond());
+  if (!BinaryOp || If->hasElseStorage())
+    return;
+
+  if (Compound) {
+    if (Compound->size() > 1)
+      return;
+  }
+
+  const SourceLocation IfLocation = If->getIfLoc();
+  const SourceLocation ThenLocation = If->getEndLoc();
----------------
felix642 wrote:

The thenLocation might not be valid in some cases.
Let's take for example this code :
```
if(a < b)
    a = b;
```

I would assume that the ThenLocation will match on the character 'b', but in your case you want to match on the ';' otherwise you'll add an extra semicolon at the end of the line.

You'll need to add a call to `Lexer::getLocForEndOfToken` to resolve this issue. Please have a look on how other checks do it.

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