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[clang-tidy] Don't report unnamed params for misc-const-correctness (#184388)

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Previously misc-const-correctness warned about non-const unnamed
parameters; but this commit excludes them because these warnings are not
actually useful. An unnamed parameter cannot be referenced at all, so
marking them as 'const' doesn't add additional information.

Also the diagnostic messages look awkward without a name.

Fixes #184330
This commit is contained in:
Donát Nagy
2026-03-04 19:02:26 +01:00
committed by GitHub
parent df52bb4c32
commit 9dc65372aa
3 changed files with 41 additions and 4 deletions
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8
clang-tools-extra/clang-tidy/misc/ConstCorrectnessCheck.cpp
View File

@@ -23,6 +23,12 @@ namespace {
// FIXME: This matcher exists in some other code-review as well.
// It should probably move to ASTMatchers.
AST_MATCHER(VarDecl, isLocal) { return Node.isLocalVarDecl(); }
// FIXME: The matcher 'hasName(Name)' asserts that its argument 'Name' is
// nonempty. Perhaps remove that assertion and replace 'isUnnamed()' with
// 'hasName("")'.
AST_MATCHER(VarDecl, isUnnamed) {
return Node.getDeclName().isIdentifier() && Node.getName().empty();
}
AST_MATCHER_P(DeclStmt, containsAnyDeclaration,
ast_matchers::internal::Matcher<Decl>, InnerMatcher) {
return ast_matchers::internal::matchesFirstInPointerRange(
@@ -148,7 +154,7 @@ void ConstCorrectnessCheck::registerMatchers(MatchFinder *Finder) {
if (AnalyzeParameters) {
const auto ParamMatcher =
parmVarDecl(unless(CommonExcludeTypes),
parmVarDecl(unless(CommonExcludeTypes), unless(isUnnamed()),
anyOf(hasType(referenceType()), hasType(pointerType())))
.bind("value");

6
clang-tools-extra/docs/clang-tidy/checks/misc/const-correctness.rst
View File

@@ -110,15 +110,15 @@ Options
Enable or disable the analysis of function parameters, like
``void foo(int* ptr)``. Only reference and pointer parameters are analyzed.
Currently, member functions (including constructors) and lambdas are excluded
from the analysis. Default is `true`.
Unnamed parameters, member functions (including constructors) and lambdas are
excluded from the analysis. Default is `true`.
.. code-block:: c++
// Warning
void function(int& param) {}
// No warning
void function(const int& param) {}
void function(const int& param, int&) {}
.. option:: WarnPointersAsValues

31
clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-parameters.cpp
View File

@@ -509,3 +509,34 @@ void struct_ptr_param_modified(Bar** bp) {
// CHECK-FIXES: void struct_ptr_param_modified(Bar** const bp) {
(*bp)->mutating_method();
}
void unnamed_parameters(int&, char*, Bar, Bar&, int[5]) {
// Unnamed parameters are never reported.
}
void unnamed_and_named_irrelevant_params(const int& X, char*, Bar Z, Bar&, int[5]) {
// No report, all parameters are excluded for various reasons.
}
void unnamed_and_named_params(int& X, int&) {
// But a named parameter is reported even if it is next to an unnamed one.
// CHECK-MESSAGES: [[@LINE-2]]:31: warning: variable 'X' of type 'int &' can be declared 'const'
// CHECK-FIXES: void unnamed_and_named_params(int const& X, int&) {
}
// If the parameter is named in the definition, its type will be updated in all
// declarations, inclunding ones where it is unnamed.
void unnamed_in_decl_named_in_def(int&);
// CHECK-FIXES: void unnamed_in_decl_named_in_def(int const&);
void unnamed_in_decl_named_in_def(int& X) {
// CHECK-MESSAGES: [[@LINE-1]]:35: warning: variable 'X' of type 'int &' can be declared 'const'
// CHECK-FIXES: void unnamed_in_decl_named_in_def(int const& X) {
}
void named_in_decl_unnamed_in_def(int& X);
void named_in_decl_unnamed_in_def(int&) {
// If the parameter is unnamed in the definition, it will not be reported, even
// if it is named in some declaration.
}