[clang-tidy] fix a crash with -fdelayed-template-parsing in UnnecessaryValueParamCheck.

Summary:
This is the same kind of bug than [[ http://reviews.llvm.org/D18238 | D18238 ]].

Fix crashes caused by deferencing null pointer when declarations parsing may be delayed.
The body of the declarations may be null.

The crashes were observed with a Windows build of clang-tidy and the following command-line.
```
command-line switches: -fms-compatibility-version=19 -fms-compatibility
```

Reviewers: alexfh

Subscribers: kimgr, LegalizeAdulthood, cfe-commits

Differential Revision: http://reviews.llvm.org/D18852

llvm-svn: 265681

1 files changed, 4 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
index e3be05ee0f2..e5757b0ec7a 100644
--- a/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
+++ b/clang-tools-extra/clang-tidy/performance/UnnecessaryValueParamCheck.cpp
@@ -51,6 +51,10 @@ void UnnecessaryValueParamCheck::check(const MatchFinder::MatchResult &Result) {
   bool IsConstQualified =
       Param->getType().getCanonicalType().isConstQualified();
 
+  // Skip declarations delayed by late template parsing without a body.
+  if (!Function->getBody())
+    return;
+
   // Do not trigger on non-const value parameters when:
   // 1. they are in a constructor definition since they can likely trigger
   //    misc-move-constructor-init which will suggest to move the argument.