[analyzer] Pass value expression for inlined defensive checks when binding null to nonnull.

The nullability checker was not suppressing false positives resulting from
inlined defensive checks when null was bound to a nonnull variable because it
was passing the entire bind statement rather than the value expression to
trackNullOrUndefValue().

This commit changes that checker to synactically match on the bind statement to
extract the value expression so it can be passed to trackNullOrUndefValue().

rdar://problem/23575439

llvm-svn: 254007

1 files changed, 30 insertions, 1 deletions

diff --git a/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
index 137dedbf4ce..89b1358a2a5 100644
--- a/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
@@ -862,6 +862,30 @@ void NullabilityChecker::checkPostStmt(const ExplicitCastExpr *CE,
   }
 }
 
+/// For a given statement performing a bind, attempt to syntactically
+/// match the expression resulting in the bound value.
+static const Expr * matchValueExprForBind(const Stmt *S) {
+  // For `x = e` the value expression is the right-hand side.
+  if (auto *BinOp = dyn_cast<BinaryOperator>(S)) {
+    if (BinOp->getOpcode() == BO_Assign)
+      return BinOp->getRHS();
+  }
+
+  // For `int x = e` the value expression is the initializer.
+  if (auto *DS = dyn_cast<DeclStmt>(S))  {
+    if (DS->isSingleDecl()) {
+      auto *VD = dyn_cast<VarDecl>(DS->getSingleDecl());
+      if (!VD)
+        return nullptr;
+
+      if (const Expr *Init = VD->getInit())
+        return Init;
+    }
+  }
+
+  return nullptr;
+}
+
 /// Propagate the nullability information through binds and warn when nullable
 /// pointer or null symbol is assigned to a pointer with a nonnull type.
 void NullabilityChecker::checkBind(SVal L, SVal V, const Stmt *S,
@@ -898,8 +922,13 @@ void NullabilityChecker::checkBind(SVal L, SVal V, const Stmt *S,
     ExplodedNode *N = C.generateErrorNode(State, &Tag);
     if (!N)
       return;
+
+    const Stmt *ValueExpr = matchValueExprForBind(S);
+    if (!ValueExpr)
+      ValueExpr = S;
+
     reportBugIfPreconditionHolds(ErrorKind::NilAssignedToNonnull, N, nullptr, C,
-                                 S);
+                                 ValueExpr);
     return;
   }
   // Intentionally missing case: '0' is bound to a reference. It is handled by