Add a new check, readability-redundant-control-flow, that check for some forms of redundant control flow statements. Currently checks for return statements at the end of a function with a void return type and continue statements at the end of looping statements.

Patch by Richard Thomson.

llvm-svn: 259362

1 files changed, 99 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.cpp
new file mode 100644
index 00000000000..54a26e24abb
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/readability/RedundantControlFlowCheck.cpp
@@ -0,0 +1,99 @@
+//===--- RedundantControlFlowCheck.cpp - clang-tidy------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "RedundantControlFlowCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace readability {
+
+namespace {
+
+const char *const RedundantReturnDiag = "redundant return statement at the end "
+                                        "of a function with a void return type";
+const char *const RedundantContinueDiag = "redundant continue statement at the "
+                                          "end of loop statement";
+
+bool isLocationInMacroExpansion(const SourceManager &SM, SourceLocation Loc) {
+  return SM.isMacroBodyExpansion(Loc) || SM.isMacroArgExpansion(Loc);
+}
+
+} // namespace
+
+void RedundantControlFlowCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      functionDecl(isDefinition(), returns(voidType()),
+                   has(compoundStmt(hasAnySubstatement(returnStmt(
+                                        unless(has(expr()))))).bind("return"))),
+      this);
+  auto CompoundContinue =
+      has(compoundStmt(hasAnySubstatement(continueStmt())).bind("continue"));
+  Finder->addMatcher(
+      stmt(anyOf(forStmt(), cxxForRangeStmt(), whileStmt(), doStmt()),
+           CompoundContinue),
+      this);
+}
+
+void RedundantControlFlowCheck::check(const MatchFinder::MatchResult &Result) {
+  if (const auto *Return = Result.Nodes.getNodeAs<CompoundStmt>("return"))
+    checkRedundantReturn(Result, Return);
+  else if (const auto *Continue =
+               Result.Nodes.getNodeAs<CompoundStmt>("continue"))
+    checkRedundantContinue(Result, Continue);
+}
+
+void RedundantControlFlowCheck::checkRedundantReturn(
+    const MatchFinder::MatchResult &Result, const CompoundStmt *Block) {
+  CompoundStmt::const_reverse_body_iterator last = Block->body_rbegin();
+  if (const auto *Return = dyn_cast<ReturnStmt>(*last))
+    issueDiagnostic(Result, Block, Return->getSourceRange(),
+                    RedundantReturnDiag);
+}
+
+void RedundantControlFlowCheck::checkRedundantContinue(
+    const MatchFinder::MatchResult &Result, const CompoundStmt *Block) {
+  CompoundStmt::const_reverse_body_iterator last = Block->body_rbegin();
+  if (const auto *Continue = dyn_cast<ContinueStmt>(*last))
+    issueDiagnostic(Result, Block, Continue->getSourceRange(),
+                    RedundantContinueDiag);
+}
+
+void RedundantControlFlowCheck::issueDiagnostic(
+    const MatchFinder::MatchResult &Result, const CompoundStmt *const Block,
+    const SourceRange &StmtRange, const char *const Diag) {
+  SourceManager &SM = *Result.SourceManager;
+  if (isLocationInMacroExpansion(SM, StmtRange.getBegin()))
+    return;
+
+  CompoundStmt::const_reverse_body_iterator Previous = ++Block->body_rbegin();
+  SourceLocation Start;
+  if (Previous != Block->body_rend())
+    Start = Lexer::findLocationAfterToken(
+        dyn_cast<Stmt>(*Previous)->getLocEnd(), tok::semi, SM,
+        Result.Context->getLangOpts(),
+        /*SkipTrailingWhitespaceAndNewLine=*/true);
+  else
+    Start = StmtRange.getBegin();
+  auto RemovedRange = CharSourceRange::getCharRange(
+      Start,
+      Lexer::findLocationAfterToken(StmtRange.getEnd(), tok::semi, SM,
+                                    Result.Context->getLangOpts(),
+                                    /*SkipTrailingWhitespaceAndNewLine=*/true));
+
+  diag(StmtRange.getBegin(), Diag) << FixItHint::CreateRemoval(RemovedRange);
+}
+
+} // namespace readability
+} // namespace tidy
+} // namespace clang