[clang-tidy] Add FixIt for swapping arguments in string-constructor-checker.

Summary:
Arguments can be swapped using fixit when they are not in macros.
This is the same implementation than SwappedArguments. Some code 
got lifted to be reused.

Others checks are not safe to be fixed as they tend to be bugs or errors.
It is better to let the user manually review them.

Reviewers: alexfh

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D19547

llvm-svn: 269208

1 files changed, 12 insertions, 4 deletions

diff --git a/clang-tools-extra/clang-tidy/misc/StringConstructorCheck.cpp b/clang-tools-extra/clang-tidy/misc/StringConstructorCheck.cpp
index 0723ec1ed40..7ff488133f3 100644
--- a/clang-tools-extra/clang-tidy/misc/StringConstructorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/StringConstructorCheck.cpp
@@ -10,6 +10,7 @@
 #include "StringConstructorCheck.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Tooling/FixIt.h"
 
 using namespace clang::ast_matchers;
 
@@ -54,7 +55,7 @@ void StringConstructorCheck::registerMatchers(MatchFinder *Finder) {
       isDefinition(),
       hasType(pointerType(pointee(isAnyCharacter(), isConstQualified()))),
       hasInitializer(ignoringParenImpCasts(BoundStringLiteral)));
-  auto ConstStrLiteral = expr(ignoringParenImpCasts(anyOf(
+  const auto ConstStrLiteral = expr(ignoringParenImpCasts(anyOf(
       BoundStringLiteral, declRefExpr(hasDeclaration(anyOf(
                               ConstPtrStrLiteralDecl, ConstStrLiteralDecl))))));
 
@@ -88,7 +89,7 @@ void StringConstructorCheck::registerMatchers(MatchFinder *Finder) {
               // Detect the expression: string("...", 0);
               hasArgument(1, ZeroExpr.bind("empty-string")),
               // Detect the expression: string("...", -4);
-              hasArgument(1, NegativeExpr.bind("negative-length")),              
+              hasArgument(1, NegativeExpr.bind("negative-length")),
               // Detect the expression: string("lit", 0x1234567);
               hasArgument(1, LargeLengthExpr.bind("large-length")),
               // Detect the expression: string("lit", 5)
@@ -100,11 +101,18 @@ void StringConstructorCheck::registerMatchers(MatchFinder *Finder) {
 }
 
 void StringConstructorCheck::check(const MatchFinder::MatchResult &Result) {
-  const auto *E = Result.Nodes.getNodeAs<Expr>("constructor");
+  const ASTContext &Ctx = *Result.Context;
+  const auto *E = Result.Nodes.getNodeAs<CXXConstructExpr>("constructor");
+  assert(E && "missing constructor expression");
   SourceLocation Loc = E->getLocStart();
 
   if (Result.Nodes.getNodeAs<Expr>("swapped-parameter")) {
-    diag(Loc, "constructor parameters are probably swapped");
+    const Expr *P0 = E->getArg(0);
+    const Expr *P1 = E->getArg(1);
+    diag(Loc, "string constructor parameters are probably swapped;"
+              " expecting string(count, character)")
+        << tooling::fixit::createReplacement(*P0, *P1, Ctx)
+        << tooling::fixit::createReplacement(*P1, *P0, Ctx);
   } else if (Result.Nodes.getNodeAs<Expr>("empty-string")) {
     diag(Loc, "constructor creating an empty string");
   } else if (Result.Nodes.getNodeAs<Expr>("negative-length")) {