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(isDefinition(), returns(voidType()),
36                    hasBody(compoundStmt(hasAnySubstatement(
37                                             returnStmt(unless(has(expr())))))
38                                .bind("return"))),
39       this);
40   Finder->addMatcher(
41       mapAnyOf(forStmt, cxxForRangeStmt, whileStmt, doStmt)
42           .with(hasBody(compoundStmt(hasAnySubstatement(continueStmt()))
43                             .bind("continue"))),
44       this);
45 }
46 
47 void RedundantControlFlowCheck::check(const MatchFinder::MatchResult &Result) {
48   if (const auto *Return = Result.Nodes.getNodeAs<CompoundStmt>("return"))
49     checkRedundantReturn(Result, Return);
50   else if (const auto *Continue =
51                Result.Nodes.getNodeAs<CompoundStmt>("continue"))
52     checkRedundantContinue(Result, Continue);
53 }
54 
55 void RedundantControlFlowCheck::checkRedundantReturn(
56     const MatchFinder::MatchResult &Result, const CompoundStmt *Block) {
57   CompoundStmt::const_reverse_body_iterator Last = Block->body_rbegin();
58   if (const auto *Return = dyn_cast<ReturnStmt>(*Last))
59     issueDiagnostic(Result, Block, Return->getSourceRange(),
60                     RedundantReturnDiag);
61 }
62 
63 void RedundantControlFlowCheck::checkRedundantContinue(
64     const MatchFinder::MatchResult &Result, const CompoundStmt *Block) {
65   CompoundStmt::const_reverse_body_iterator Last = Block->body_rbegin();
66   if (const auto *Continue = dyn_cast<ContinueStmt>(*Last))
67     issueDiagnostic(Result, Block, Continue->getSourceRange(),
68                     RedundantContinueDiag);
69 }
70 
71 void RedundantControlFlowCheck::issueDiagnostic(
72     const MatchFinder::MatchResult &Result, const CompoundStmt *const Block,
73     const SourceRange &StmtRange, const char *const Diag) {
74   SourceManager &SM = *Result.SourceManager;
75   if (isLocationInMacroExpansion(SM, StmtRange.getBegin()))
76     return;
77 
78   CompoundStmt::const_reverse_body_iterator Previous = ++Block->body_rbegin();
79   SourceLocation Start;
80   if (Previous != Block->body_rend())
81     Start = Lexer::findLocationAfterToken(
82         cast<Stmt>(*Previous)->getEndLoc(), tok::semi, SM, getLangOpts(),
83         /*SkipTrailingWhitespaceAndNewLine=*/true);
84   if (!Start.isValid())
85     Start = StmtRange.getBegin();
86   auto RemovedRange = CharSourceRange::getCharRange(
87       Start, Lexer::findLocationAfterToken(
88                  StmtRange.getEnd(), tok::semi, SM, getLangOpts(),
89                  /*SkipTrailingWhitespaceAndNewLine=*/true));
90 
91   diag(StmtRange.getBegin(), Diag) << FixItHint::CreateRemoval(RemovedRange);
92 }
93 
94 } // namespace readability
95 } // namespace tidy
96 } // namespace clang
97