[Sema] Push and Pop Expression Evaluation Context Records at the start and end of function definitions

This patch creates a new context for every function definition we enter.
Currently we do not push and pop on these, usually working off of the global
context record added in the Sema constructor, which never gets popped.

Differential Revision: https://reviews.llvm.org/D54014

llvm-svn: 348434

clang/lib/Sema/SemaDecl.cpp

@@ -12828,6 +12828,7 @@ Decl *Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Decl *D,
     // Parsing the function declaration failed in some way. Push on a fake scope
     // anyway so we can try to parse the function body.
     PushFunctionScope();
+    PushExpressionEvaluationContext(ExprEvalContexts.back().Context);
     return D;
   }
 
@@ -12838,6 +12839,11 @@ Decl *Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Decl *D,
   else
     FD = cast<FunctionDecl>(D);
 
+  // Do not push if it is a lambda because one is already pushed when building
+  // the lambda in ActOnStartOfLambdaDefinition().
+  if (!isLambdaCallOperator(FD))
+    PushExpressionEvaluationContext(ExprEvalContexts.back().Context);
+
   // Check for defining attributes before the check for redefinition.
   if (const auto *Attr = FD->getAttr<AliasAttr>()) {
     Diag(Attr->getLocation(), diag::err_alias_is_definition) << FD << 0;
@@ -13046,6 +13052,21 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *D, Stmt *BodyArg) {
   return ActOnFinishFunctionBody(D, BodyArg, false);
 }
 
+/// RAII object that pops an ExpressionEvaluationContext when exiting a function
+/// body.
+class ExitFunctionBodyRAII {
+public:
+  ExitFunctionBodyRAII(Sema &S, bool IsLambda) : S(S), IsLambda(IsLambda) {}
+  ~ExitFunctionBodyRAII() {
+    if (!IsLambda)
+      S.PopExpressionEvaluationContext();
+  }
+
+private:
+  Sema &S;
+  bool IsLambda = false;
+};
+
 Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
                                     bool IsInstantiation) {
   FunctionDecl *FD = dcl ? dcl->getAsFunction() : nullptr;
@@ -13056,6 +13077,11 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
   if (getLangOpts().CoroutinesTS && getCurFunction()->isCoroutine())
     CheckCompletedCoroutineBody(FD, Body);
 
+  // Do not call PopExpressionEvaluationContext() if it is a lambda because one
+  // is already popped when finishing the lambda in BuildLambdaExpr(). This is
+  // meant to pop the context added in ActOnStartOfFunctionDef().
+  ExitFunctionBodyRAII ExitRAII(*this, isLambdaCallOperator(FD));
+
   if (FD) {
     FD->setBody(Body);
     FD->setWillHaveBody(false);

clang/lib/Sema/SemaDeclObjC.cpp

@@ -363,6 +363,8 @@ void Sema::ActOnStartOfObjCMethodDef(Scope *FnBodyScope, Decl *D) {
   assert((getCurMethodDecl() == nullptr) && "Methodparsing confused");
   ObjCMethodDecl *MDecl = dyn_cast_or_null<ObjCMethodDecl>(D);
 
+  PushExpressionEvaluationContext(ExprEvalContexts.back().Context);
+
   // If we don't have a valid method decl, simply return.
   if (!MDecl)
     return;

clang/lib/Sema/SemaExpr.cpp

@@ -14414,11 +14414,8 @@ void Sema::PopExpressionEvaluationContext() {
   // Pop the current expression evaluation context off the stack.
   ExprEvalContexts.pop_back();
 
-  if (!ExprEvalContexts.empty())
-    ExprEvalContexts.back().NumTypos += NumTypos;
-  else
-    assert(NumTypos == 0 && "There are outstanding typos after popping the "
-                            "last ExpressionEvaluationContextRecord");
+  // The global expression evaluation context record is never popped.
+  ExprEvalContexts.back().NumTypos += NumTypos;
 }
 
 void Sema::DiscardCleanupsInEvaluationContext() {