================
@@ -0,0 +1,115 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "StringViewConversionsCheck.h"
+#include "clang/AST/Expr.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::performance {
+
+static auto getStringTypeMatcher(StringRef CharType) {
+ return hasCanonicalType(hasDeclaration(cxxRecordDecl(hasName(CharType))));
+}
+
+void StringViewConversionsCheck::registerMatchers(MatchFinder *Finder) {
+ // Matchers for std::basic_[w|u8|u16|u32]string[_view] families.
+ const auto IsStdString = getStringTypeMatcher("::std::basic_string");
+ const auto IsStdStringView =
getStringTypeMatcher("::std::basic_string_view");
+
+ // Matches pointer to any character type (char*, etc.) or array of any
+ // character type (char[], etc.).
+ const auto IsCharPointerOrArray =
+ anyOf(hasType(pointerType(pointee(isAnyCharacter()))),
+ hasType(arrayType(hasElementType(isAnyCharacter()))));
+
+ const auto ImplicitlyConvertibleToStringView =
+ expr(anyOf(hasType(IsStdStringView), IsCharPointerOrArray,
+ hasType(IsStdString)))
+ .bind("originalStringView");
+
+ // Matches std::string construction from a string_view-convertible
expression:
+ // - Direct construction: std::string{sv}, std::string{s}
+ // - Copy from existing string: std::string(s) where s is std::string
+ const auto RedundantStringConstruction = cxxConstructExpr(
+ hasType(IsStdString),
+ hasArgument(0, ignoringImplicit(ImplicitlyConvertibleToStringView)),
+ unless(hasArgument(1, unless(cxxDefaultArgExpr()))));
+
+ // Matches functional cast syntax: std::string(expr):
+ // std::string(sv), std::string("literal")
+ const auto RedundantFunctionalCast = cxxFunctionalCastExpr(
+ hasType(IsStdString), hasDescendant(RedundantStringConstruction));
+
+ // Match method calls on std::string that modify or use the string,
+ // such as operator+, append(), substr(), c_str(), etc.
+ const auto HasStringOperatorCall = hasDescendant(cxxOperatorCallExpr(
+ hasOverloadedOperatorName("+"), hasType(IsStdString)));
+ const auto HasStringMethodCall =
+ hasDescendant(cxxMemberCallExpr(on(hasType(IsStdString))));
+
+ const auto IsCallReturningString = callExpr(hasType(IsStdString));
+ const auto IsImplicitStringViewFromCall =
+ cxxConstructExpr(hasType(IsStdStringView),
+ hasArgument(0,
ignoringImplicit(IsCallReturningString)));
+
+ // Main matcher: finds function calls where:
+ // 1. A parameter has type string_view
+ // 2. The corresponding argument contains a redundant std::string
construction
+ // (either functional cast syntax or direct construction/brace init)
+ // 3. The argument does NOT involve:
+ // - String concatenation with operator+ (string_view doesn't support it)
+ // - Method calls on the std::string (like append(), substr(), etc.)
+ Finder->addMatcher(
+ callExpr(forEachArgumentWithParam(
+ expr(hasType(IsStdStringView),
+ // Ignore cases where the argument is a function call
+ unless(ignoringParenImpCasts(IsImplicitStringViewFromCall)),
+ // Match either syntax for std::string construction
+ hasDescendant(expr(anyOf(RedundantFunctionalCast,
+ RedundantStringConstruction))
+ .bind("redundantExpr")),
+ // Exclude cases of std::string methods or operator+ calls
+ unless(anyOf(HasStringOperatorCall, HasStringMethodCall)))
+ .bind("expr"),
+ parmVarDecl(hasType(IsStdStringView)))),
+ this);
+}
+
+void StringViewConversionsCheck::check(const MatchFinder::MatchResult &Result)
{
+ const auto *ParamExpr = Result.Nodes.getNodeAs<Expr>("expr");
+ assert(ParamExpr);
+
+ const auto *RedundantExpr = Result.Nodes.getNodeAs<Expr>("redundantExpr");
+ assert(RedundantExpr);
+
+ const auto *OriginalExpr =
Result.Nodes.getNodeAs<Expr>("originalStringView");
+ assert(OriginalExpr);
----------------
vbvictor wrote:
Could be
```suggestion
const auto *ParamExpr = Result.Nodes.getNodeAs<Expr>("expr");
const auto *RedundantExpr = Result.Nodes.getNodeAs<Expr>("redundantExpr");
const auto *OriginalExpr = Result.Nodes.getNodeAs<Expr>("originalStringView");
assert(RedundantExpr && ParamExpr && OriginalExpr);
```
https://github.com/llvm/llvm-project/pull/174288
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