[clang-tidy] modernize-use-equals-default avoid adding redundant semicolons

Summary:
`modernize-use-equals-default` replaces default constructors/destructors with `= default;`. When the optional semicolon after a member function is present, this results in two consecutive semicolons.

This patch checks to see if the next non-comment token after the code to be replaced is a semicolon, and if so offers a replacement of `= default` rather than `= default;`.

This patch adds trailing comments and semicolons to about 5 existing tests.

Reviewers: malcolm.parsons, angelgarcia, aaron.ballman, alexfh

Patch by: poelmanc

Subscribers: MyDeveloperDay, JonasToth, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70144

Author: Mitchell Balan

clang-tools-extra/clang-tidy/modernize/UseEqualsDefaultCheck.cpp

@@ -10,6 +10,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Lexer.h"
+#include "../utils/LexerUtils.h"
 
 using namespace clang::ast_matchers;
 
@@ -302,9 +303,16 @@ void UseEqualsDefaultCheck::check(const MatchFinder::MatchResult &Result) {
   auto Diag = diag(Location, "use '= default' to define a trivial " +
                                  SpecialFunctionName);
 
-  if (ApplyFix)
-    Diag << FixItHint::CreateReplacement(Body->getSourceRange(), "= default;")
+  if (ApplyFix) {
+    // Skipping comments, check for a semicolon after Body->getSourceRange()
+    Optional<Token> Token = utils::lexer::findNextTokenSkippingComments(
+        Body->getSourceRange().getEnd().getLocWithOffset(1),
+        Result.Context->getSourceManager(), Result.Context->getLangOpts());
+    StringRef Replacement =
+        Token && Token->is(tok::semi) ? "= default" : "= default;";
+    Diag << FixItHint::CreateReplacement(Body->getSourceRange(), Replacement)
          << RemoveInitializers;
+  }
 }
 
 } // namespace modernize

clang-tools-extra/clang-tidy/utils/LexerUtils.cpp

@@ -68,6 +68,16 @@ SourceLocation findNextTerminator(SourceLocation Start, const SourceManager &SM,
   return findNextAnyTokenKind(Start, SM, LangOpts, tok::comma, tok::semi);
 }
 
+Optional<Token> findNextTokenSkippingComments(SourceLocation Start,
+                                              const SourceManager &SM,
+                                              const LangOptions &LangOpts) {
+  Optional<Token> CurrentToken;
+  do {
+    CurrentToken = Lexer::findNextToken(Start, SM, LangOpts);
+  } while (CurrentToken && CurrentToken->is(tok::comment));
+  return CurrentToken;
+}
+
 bool rangeContainsExpansionsOrDirectives(SourceRange Range,
                                          const SourceManager &SM,
                                          const LangOptions &LangOpts) {

clang-tools-extra/clang-tidy/utils/LexerUtils.h

@@ -80,6 +80,11 @@ SourceLocation findNextAnyTokenKind(SourceLocation Start,
   }
 }
 
+// Finds next token that's not a comment.
+Optional<Token> findNextTokenSkippingComments(SourceLocation Start,
+                                              const SourceManager &SM,
+                                              const LangOptions &LangOpts);
+
 /// Re-lex the provide \p Range and return \c false if either a macro spans
 /// multiple tokens, a pre-processor directive or failure to retrieve the
 /// next token is found, otherwise \c true.

clang-tools-extra/docs/ReleaseNotes.rst

@@ -158,6 +158,10 @@ Improvements to clang-tidy
 - The 'objc-avoid-spinlock' check was renamed to :doc:`darwin-avoid-spinlock
   <clang-tidy/checks/darwin-avoid-spinlock>`
 
+- The :doc:`modernize-use-equals-default
+  <clang-tidy/checks/modernize-use-equals-default>` fix no longer adds
+  semicolons where they would be redundant.
+
 - New :doc:`readability-redundant-access-specifiers
   <clang-tidy/checks/readability-redundant-access-specifiers>` check.
 

clang-tools-extra/test/clang-tidy/checkers/modernize-use-equals-default-copy.cpp

@@ -119,7 +119,7 @@ Empty &Empty::operator=(const Empty &Other) { return *this; }
 struct BF {
   BF() = default;
   BF(const BF &Other) : Field1(Other.Field1), Field2(Other.Field2), Field3(Other.Field3),
-                        Field4(Other.Field4) {}
+                        Field4(Other.Field4) {};
   // CHECK-MESSAGES: :[[@LINE-2]]:3: warning: use '= default'
   // CHECK-FIXES: BF(const BF &Other) {{$}}
   // CHECK-FIXES:                     = default;

clang-tools-extra/test/clang-tidy/checkers/modernize-use-equals-default.cpp

@@ -7,7 +7,7 @@ class OL {
   ~OL();
 };
 
-OL::OL() {}
+OL::OL() {};
 // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: use '= default' to define a trivial default constructor [modernize-use-equals-default]
 // CHECK-FIXES: OL::OL() = default;
 OL::~OL() {}
@@ -17,9 +17,9 @@ OL::~OL() {}
 // Inline definitions.
 class IL {
 public:
-  IL() {}
+  IL() {} 	 ; // Note embedded tab on this line
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
-  // CHECK-FIXES: IL() = default;
+  // CHECK-FIXES: IL() = default 	 ; // Note embedded tab on this line
   ~IL() {}
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
   // CHECK-FIXES: ~IL() = default;
@@ -46,18 +46,20 @@ class IA {
 // Default member initializer
 class DMI {
 public:
-  DMI() {}
-  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
-  // CHECK-FIXES: DMI() = default;
+  DMI() {} // Comment before semi-colon on next line
+  ;
+  // CHECK-MESSAGES: :[[@LINE-2]]:3: warning: use '= default'
+  // CHECK-FIXES: DMI() = default // Comment before semi-colon on next line
+  // CHECK-FIXES-NEXT:   ;
   int Field = 5;
 };
 
 // Class member
 class CM {
 public:
-  CM() {}
+  CM() {} /* Comments */ /* before */ /* semicolon */;
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
-  // CHECK-FIXES: CM() = default;
+  // CHECK-FIXES: CM() = default /* Comments */ /* before */ /* semicolon */;
   OL o;
 };
 
@@ -66,7 +68,7 @@ class Priv {
   Priv() {}
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
   // CHECK-FIXES: Priv() = default;
-  ~Priv() {}
+  ~Priv() {};
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
   // CHECK-FIXES: ~Priv() = default;
 };