Fixed a crash in code completion.

[ilya-biryukov]

Summary

The crash occured when FunctionDecl was parsed with an initializer.

[bkramer]

lg

[ilya-biryukov]

• Fix to account for change in the interface of ParseExpressionList.

lib/Parse/ParseDecl.cpp

if (isTokenEqualOrEqualTypo()) {
     ExprVector Exprs;
     CommaLocsTy CommaLocs;
 
     if (getLangOpts().CPlusPlus && D.getCXXScopeSpec().isSet()) {
       EnterScope(0);
       Actions.ActOnCXXEnterDeclInitializer(getCurScope(), ThisDecl);
     }
 
-    if (ParseExpressionList(Exprs, CommaLocs, [&] {
-          Actions.CodeCompleteConstructor(getCurScope(),
-                 cast<VarDecl>(ThisDecl)->getType()->getCanonicalTypeInternal(),
-                                          ThisDecl->getLocation(), Exprs);
-       })) {
+    llvm::function_ref<void()> ExprListCompleter;
+    auto ThisVarDecl = dyn_cast_or_null<VarDecl>(ThisDecl);
+    auto ConstructorCompleter = [&, ThisVarDecl] {
+      Actions.CodeCompleteConstructor(
+          getCurScope(), ThisVarDecl->getType()->getCanonicalTypeInternal(),
+    };
+    if (ThisVarDecl) {
+      // ParseExpressionList can sometimes succeed even when ThisDecl is not
+      // VarDecl. This is an error and it is reported in a call to
+      // Actions.ActOnInitializerError(). However, we call
+      // CodeCompleteConstructor only on VarDecls, falling back to default
+      // completer in other cases.
+      ExprListCompleter = ConstructorCompleter;
+    }
+
+    if (ParseExpressionList(Exprs, CommaLocs, ExprListCompleter)) {
       Actions.ActOnInitializerError(ThisDecl);
       SkipUntil(tok::r_paren, StopAtSemi);
 
       if (getLangOpts().CPlusPlus && D.getCXXScopeSpec().isSet()) {
         Actions.ActOnCXXExitDeclInitializer(getCurScope(), ThisDecl);
         ExitScope();
       }
     } else {

test/CodeCompletion/crash-func-init.cpp

+int (*foo(int a))(flo
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:1:21 %s -o - \
+// RUN:            | FileCheck %s
+// CHECK: COMPLETION: float