1 //===--- RedundantControlFlowCheck.cpp - clang-tidy------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "RedundantControlFlowCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/Lex/Lexer.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace readability {
19 
20 namespace {
21 
22 const char *const RedundantReturnDiag = "redundant return statement at the end "
23                                         "of a function with a void return type";
24 const char *const RedundantContinueDiag = "redundant continue statement at the "
25                                           "end of loop statement";
26 
27 bool isLocationInMacroExpansion(const SourceManager &SM, SourceLocation Loc) {
28   return SM.isMacroBodyExpansion(Loc) || SM.isMacroArgExpansion(Loc);
29 }
30 
31 } // namespace
32 
33 void RedundantControlFlowCheck::registerMatchers(MatchFinder *Finder) {
34   Finder->addMatcher(
35       functionDecl(
36           isDefinition(), returns(voidType()),
37           has(compoundStmt(hasAnySubstatement(returnStmt(unless(has(expr())))))
38                   .bind("return"))),
39       this);
40   auto CompoundContinue =
41       has(compoundStmt(hasAnySubstatement(continueStmt())).bind("continue"));
42   Finder->addMatcher(
43       stmt(anyOf(forStmt(), cxxForRangeStmt(), whileStmt(), doStmt()),
44            CompoundContinue),
45       this);
46 }
47 
48 void RedundantControlFlowCheck::check(const MatchFinder::MatchResult &Result) {
49   if (const auto *Return = Result.Nodes.getNodeAs<CompoundStmt>("return"))
50     checkRedundantReturn(Result, Return);
51   else if (const auto *Continue =
52                Result.Nodes.getNodeAs<CompoundStmt>("continue"))
53     checkRedundantContinue(Result, Continue);
54 }
55 
56 void RedundantControlFlowCheck::checkRedundantReturn(
57     const MatchFinder::MatchResult &Result, const CompoundStmt *Block) {
58   CompoundStmt::const_reverse_body_iterator last = Block->body_rbegin();
59   if (const auto *Return = dyn_cast<ReturnStmt>(*last))
60     issueDiagnostic(Result, Block, Return->getSourceRange(),
61                     RedundantReturnDiag);
62 }
63 
64 void RedundantControlFlowCheck::checkRedundantContinue(
65     const MatchFinder::MatchResult &Result, const CompoundStmt *Block) {
66   CompoundStmt::const_reverse_body_iterator last = Block->body_rbegin();
67   if (const auto *Continue = dyn_cast<ContinueStmt>(*last))
68     issueDiagnostic(Result, Block, Continue->getSourceRange(),
69                     RedundantContinueDiag);
70 }
71 
72 void RedundantControlFlowCheck::issueDiagnostic(
73     const MatchFinder::MatchResult &Result, const CompoundStmt *const Block,
74     const SourceRange &StmtRange, const char *const Diag) {
75   SourceManager &SM = *Result.SourceManager;
76   if (isLocationInMacroExpansion(SM, StmtRange.getBegin()))
77     return;
78 
79   CompoundStmt::const_reverse_body_iterator Previous = ++Block->body_rbegin();
80   SourceLocation Start;
81   if (Previous != Block->body_rend())
82     Start = Lexer::findLocationAfterToken(
83         dyn_cast<Stmt>(*Previous)->getEndLoc(), tok::semi, SM, getLangOpts(),
84         /*SkipTrailingWhitespaceAndNewLine=*/true);
85   if (!Start.isValid())
86     Start = StmtRange.getBegin();
87   auto RemovedRange = CharSourceRange::getCharRange(
88       Start, Lexer::findLocationAfterToken(
89                  StmtRange.getEnd(), tok::semi, SM, getLangOpts(),
90                  /*SkipTrailingWhitespaceAndNewLine=*/true));
91 
92   diag(StmtRange.getBegin(), Diag) << FixItHint::CreateRemoval(RemovedRange);
93 }
94 
95 } // namespace readability
96 } // namespace tidy
97 } // namespace clang
98