1 //===--- RedundantControlFlowCheck.cpp - clang-tidy------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "RedundantControlFlowCheck.h"
11 #include "clang/AST/ASTContext.h"
12 #include "clang/ASTMatchers/ASTMatchFinder.h"
13 #include "clang/Lex/Lexer.h"
14 
15 using namespace clang::ast_matchers;
16 
17 namespace clang {
18 namespace tidy {
19 namespace readability {
20 
21 namespace {
22 
23 const char *const RedundantReturnDiag = "redundant return statement at the end "
24                                         "of a function with a void return type";
25 const char *const RedundantContinueDiag = "redundant continue statement at the "
26                                           "end of loop statement";
27 
28 bool isLocationInMacroExpansion(const SourceManager &SM, SourceLocation Loc) {
29   return SM.isMacroBodyExpansion(Loc) || SM.isMacroArgExpansion(Loc);
30 }
31 
32 } // namespace
33 
34 void RedundantControlFlowCheck::registerMatchers(MatchFinder *Finder) {
35   Finder->addMatcher(
36       functionDecl(isDefinition(), returns(voidType()),
37                    has(compoundStmt(hasAnySubstatement(returnStmt(
38                                         unless(has(expr()))))).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)->getLocEnd(), tok::semi, SM,
84         Result.Context->getLangOpts(),
85         /*SkipTrailingWhitespaceAndNewLine=*/true);
86   else
87     Start = StmtRange.getBegin();
88   auto RemovedRange = CharSourceRange::getCharRange(
89       Start,
90       Lexer::findLocationAfterToken(StmtRange.getEnd(), tok::semi, SM,
91                                     Result.Context->getLangOpts(),
92                                     /*SkipTrailingWhitespaceAndNewLine=*/true));
93 
94   diag(StmtRange.getBegin(), Diag) << FixItHint::CreateRemoval(RemovedRange);
95 }
96 
97 } // namespace readability
98 } // namespace tidy
99 } // namespace clang
100