[AST] Build recovery expressions by default for C++.

[hokein]

fix the clangd test.

[sammccall]

Do you also want to update LangOpts.td to make the default for the langopt equal to CPlusPlus?
(I saw other opts doing that, not sure exactly what it affects, may be voodoo cargo cult stuff)

clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp

1198–1200

Why did the original test start failing? Is this a regression?

(This certainly seems OK to regress and fix later, but there may be other consequences?)

[hokein]

address review comments.

[hokein]

In D76696#1939513, @sammccall wrote:

Do you also want to update LangOpts.td to make the default for the langopt equal to CPlusPlus?
(I saw other opts doing that, not sure exactly what it affects, may be voodoo cargo cult stuff)

ah, I missed that.

clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp

1198–1200

yes, but I didn't dig into it, it is likely a regression, added a FIXME (looking at other cases in this test, they just use 10 as the parameter).

[ebevhan]

We found an odd case in our downstream fork after this patch landed. We have a diagnostic in CheckVariableDeclarationType that checks for automatic variables that are too large for the stack address space, and it chokes on the testcase Parser/objcxx11-invalid-lambda.cpp:

void foo() {  // expected-note {{to match this '{'}}
  int bar;
  auto baz = [
      bar(  // expected-note {{to match this '('}} expected-note {{to match this '('}}
        foo_undeclared() // expected-error{{use of undeclared identifier 'foo_undeclared'}}
      /* ) */
    ] () { };   // expected-error{{expected ')'}}
}               // expected-error{{expected ')'}} expected-error {{expected ',' or ']'}} expected-error{{expected ';' at end of declaration}} expected-error{{expected '}'}}

When the lambda is parsed, the parsing of the initializer expression of the 'bar' capture fails since the paren is unbalanced, so it will build:

ParenListExpr 0xc592ce8 'NULL TYPE' contains-errors
`-RecoveryExpr 0xc592cc0 '<dependent type>' contains-errors lvalue
  `-UnresolvedLookupExpr 0xc592c38 '<overloaded function type>' lvalue (ADL) = 'foo_undeclared' empty

Then, when building the lambda closure type, it will be given an auto member for bar with its type deduced to AutoType 0xc592d40 'auto' dependent:

CXXRecordDecl 0xdfeb798 <...> col:14 implicit class definition
|-DefinitionData lambda pass_in_registers standard_layout trivially_copyable can_const_default_init
| |-DefaultConstructor
| |-CopyConstructor simple trivial has_const_param needs_implicit implicit_has_const_param
| |-MoveConstructor exists simple trivial needs_implicit
| |-CopyAssignment trivial has_const_param needs_implicit implicit_has_const_param
| |-MoveAssignment
| `-Destructor simple irrelevant trivial
|-CXXMethodDecl 0xdfeb8d0 <line:10:8, col:12> line:5:14 operator() 'void () const' inline
| `-CompoundStmt 0xdfeba20 <line:10:10, col:12>
|-FieldDecl 0xdfeba58 <line:6:7> col:7 implicit 'auto'
`-CXXDestructorDecl 0xdfebb08 <line:5:14> col:14 implicit referenced ~ 'void () noexcept' inline default trivial

However, this just means that baz has a very odd type; it's a variable of closure type that contains a dependent member that will never be resolved. Our diagnostic breaks, since the variable's type isn't dependent, but it has a member which is, and we can't take the size of that.

Is the lambda parser really supposed to build this kind of odd type when faced with RecoveryExpr?

[sammccall]

In D76696#1943657, @ebevhan wrote:

However, this just means that baz has a very odd type; it's a variable of closure type that contains a dependent member that will never be resolved. Our diagnostic breaks, since the variable's type isn't dependent, but it has a member which is, and we can't take the size of that.

Interesting. Simply turning this off for lambdas isn't enough. The following crashes clang for me:

class X {
  decltype(unresolved()) foo;
};
constexpr int s = sizeof(X);

@hokein I think we need to revert until we find a solution for this. I suspect this is going to mean adding the error bit to type and... dropping members that have it set? Or marking them as invalid?

[hokein]

Thanks for the test case. Reverted in https://github.com/llvm/llvm-project/commit/62dea6e9be31b100962f9ad41c1b79467a53f6cd for now. Adding the error-bit to type looks like a right direction.

[hubert.reinterpretcast]

We have also encountered crashes in downstream testing caused by this using just the vanilla source from trunk. When there is a proposed fix, please let us know so we can test. Thanks.

[sammccall]

@ebevhan Thanks again for the testcase. I've added a reduced version in 47e7bdb10732e6f140adce39a1bc34e3ee2a6ea6 to ensure this is fixed on re-land.
This particular case can be fixed by marking the decl as invalid I think, I'm curious how this generalizes.

In D76696#1944014, @hubert.reinterpretcast wrote:

We have also encountered crashes in downstream testing caused by this using just the vanilla source from trunk. When there is a proposed fix, please let us know so we can test. Thanks.

We can try but it would be very useful to have details, no idea whether it's going to be the same issue and the more we know about the easier it is to improve the design.
Can you describe the case at all? Any chance of a minimal example? Ideally we'd check it in.

[hubert.reinterpretcast]

In D76696#1944014, @hubert.reinterpretcast wrote:

We have also encountered crashes in downstream testing caused by this using just the vanilla source from trunk. When there is a proposed fix, please let us know so we can test. Thanks.

We can try but it would be very useful to have details, no idea whether it's going to be the same issue and the more we know about the easier it is to improve the design.
Can you describe the case at all? Any chance of a minimal example? Ideally we'd check it in.

All of them appear to have unresolved names in constexpr evaluation. It is likely to be the same issue.

[sammccall]

In D76696#1944625, @hubert.reinterpretcast wrote:

All of them appear to have unresolved names in constexpr evaluation. It is likely to be the same issue.

The general scheme is probably common: unresolved expr -> ??? -> an expression is dependent but not marked as such -> constant evaluation crashes.

But the ??? matters, as that's where the fix is.
In the case above: expr is used in a member of X, and X is not a dependent type, so sizeof(X) is not considered dependent

[hubert.reinterpretcast]

In D76696#1944784, @sammccall wrote:

The general scheme is probably common: unresolved expr -> ??? -> an expression is dependent but not marked as such -> constant evaluation crashes.

But the ??? matters, as that's where the fix is.
In the case above: expr is used in a member of X, and X is not a dependent type, so sizeof(X) is not considered dependent

The context, if I understand correctly for the cases I am seeing, boil down to:

• Value of a member initializer for a constexpr constructor
• Bitfield width

[sammccall]

In D76696#1944825, @hubert.reinterpretcast wrote:

In D76696#1944784, @sammccall wrote:

The general scheme is probably common: unresolved expr -> ??? -> an expression is dependent but not marked as such -> constant evaluation crashes.

But the ??? matters, as that's where the fix is.
In the case above: expr is used in a member of X, and X is not a dependent type, so sizeof(X) is not considered dependent

The context, if I understand correctly for the cases I am seeing, boil down to:

• Value of a member initializer for a constexpr constructor

struct X {
  int Y;
  constexpr X() : Y(foo()) {]
};

This will need a different fix I think. Maybe just isPotentialConstantExpr needs to bail out if there are errors.

• Bitfield width

struct X { int Y : foo(); };
constexpr int Z = sizeof(X);

I think this one is just another case of marking the fielddecl as invalid.

clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp

int main() {
       // Macro expansions.
       $p^FOO 10, ^ );
     })cpp",
                                  // Macro arguments.
                                  R"cpp(
     int foo(int a, int b, int c);
     int main() {
     #define ID(X) X
-      ID(foo $p^( foo(10), ^ ))
+      // FIXME: figure out why ID(foo (foo(10), )) doesn't work when preserving
+      // the recovery expression.
+      ID(foo $p^( 10, ^ ))
     })cpp"};
 
   for (auto Test : Tests) {
     Annotations Code(Test);
     EXPECT_EQ(signatures(Code.code(), Code.point()).argListStart,
               Code.point("p"))
         << "Test source:" << Test;
   }

clang/include/clang/Basic/LangOptions.def

 LANGOPT(NoMathBuiltin     , 1, 0, "disable math builtin functions")
 LANGOPT(GNUAsm            , 1, 1, "GNU-style inline assembly")
 LANGOPT(Coroutines        , 1, 0, "C++20 coroutines")
 LANGOPT(DllExportInlines  , 1, 1, "dllexported classes dllexport inline methods")
 LANGOPT(RelaxedTemplateTemplateArgs, 1, 0, "C++17 relaxed matching of template template arguments")
 
 LANGOPT(DoubleSquareBracketAttributes, 1, 0, "'[[]]' attributes extension for all language standard modes")
 
-COMPATIBLE_LANGOPT(RecoveryAST, 1, 0, "Preserve expressions in AST when encountering errors")
+COMPATIBLE_LANGOPT(RecoveryAST, 1, CPlusPlus, "Preserve expressions in AST when encountering errors")
 
 BENIGN_LANGOPT(ThreadsafeStatics , 1, 1, "thread-safe static initializers")
 LANGOPT(POSIXThreads      , 1, 0, "POSIX thread support")
 LANGOPT(Blocks            , 1, 0, "blocks extension to C")
 BENIGN_LANGOPT(EmitAllDecls      , 1, 0, "emitting all declarations")
 LANGOPT(MathErrno         , 1, 1, "errno in math functions")
 BENIGN_LANGOPT(HeinousExtensions , 1, 0, "extensions that we really don't like and may be ripped out at any time")
 LANGOPT(Modules           , 1, 0, "modules semantics")

clang/lib/Frontend/CompilerInvocation.cpp

Diags.Report(diag::err_fe_invalid_alignment) << A->getAsString(Args)
                                                  << A->getValue();
     Opts.NewAlignOverride = 0;
   }
   Opts.ConceptSatisfactionCaching =
       !Args.hasArg(OPT_fno_concept_satisfaction_caching);
   if (Args.hasArg(OPT_fconcepts_ts))
     Diags.Report(diag::warn_fe_concepts_ts_flag);
   Opts.RecoveryAST =
-      Args.hasFlag(OPT_frecovery_ast, OPT_fno_recovery_ast, false);
+      Args.hasFlag(OPT_frecovery_ast, OPT_fno_recovery_ast, Opts.CPlusPlus);
   Opts.HeinousExtensions = Args.hasArg(OPT_fheinous_gnu_extensions);
   Opts.AccessControl = !Args.hasArg(OPT_fno_access_control);
   Opts.ElideConstructors = !Args.hasArg(OPT_fno_elide_constructors);
   Opts.MathErrno = !Opts.OpenCL && Args.hasArg(OPT_fmath_errno);
   Opts.InstantiationDepth =
       getLastArgIntValue(Args, OPT_ftemplate_depth, 1024, Diags);
   Opts.ArrowDepth =
       getLastArgIntValue(Args, OPT_foperator_arrow_depth, 256, Diags);

clang/lib/Sema/SemaExpr.cpp

 
 bool Sema::IsDependentFunctionNameExpr(Expr *E) {
   assert(E->isTypeDependent());
   return isa<UnresolvedLookupExpr>(E);
 }
 
 ExprResult Sema::CreateRecoveryExpr(SourceLocation Begin, SourceLocation End,
                                     ArrayRef<Expr *> SubExprs) {
-  // FIXME: enable it for C++, RecoveryExpr is type-dependent to suppress
-  // bogus diagnostics and this trick does not work in C.
+  // RecoveryExpr is type-dependent to suppress bogus diagnostics and this trick
+  // does not work in C.
   // FIXME: use containsErrors() to suppress unwanted diags in C.
   if (!Context.getLangOpts().RecoveryAST)
     return ExprError();
 
   if (isSFINAEContext())
     return ExprError();
 
   return RecoveryExpr::Create(Context, Begin, End, SubExprs);
 }

clang/test/OpenMP/target_update_from_messages.cpp

struct S8 {
   void foo() {
 #pragma omp target update from(*this) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
     {}
 #pragma omp target update from(*(this->ptr)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(*(this->S->i+this->S->p)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(*(this->S->i+this->S->s6[0].pp)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(*(a+this->ptr)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(*(*(this->ptr)+a+this->ptr)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
-#pragma omp target update from(*(this+this)) // expected-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}} expected-error {{invalid operands to binary expression ('S8 *' and 'S8 *')}}
+#pragma omp target update from(*(this+this)) // expected-error {{invalid operands to binary expression ('S8 *' and 'S8 *')}}
   }
 };
 
 S3 h;
 #pragma omp threadprivate(h) // expected-note 2 {{defined as threadprivate or thread local}}
 
 typedef int to;
 

 #pragma omp target update from(**(BB+y)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(*(m+*offset)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(**(*offset+BB)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(**(y+BB)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(*(*offset+m)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(**(-(*offset)+BB+*m)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(**(*(*(&offset))+BB-*m)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update from(*(x+*(y+*(**BB+BBB)+s7.i))) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
-#pragma omp target update from(*(m+(m))) // expected-error {{invalid operands to binary expression ('int *' and 'int *')}} expected-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
-#pragma omp target update from(*(1+y+y)) // expected-error {{indirection requires pointer operand ('int' invalid)}} expected-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
+#pragma omp target update from(*(m+(m))) // expected-error {{invalid operands to binary expression ('int *' and 'int *')}}
+#pragma omp target update from(*(1+y+y)) // expected-error {{indirection requires pointer operand ('int' invalid)}}
 #pragma omp target data map(to: s7.i)
   {
 #pragma omp target update from(s7.x)
   }
 
   return tmain<int, 3>(argc)+tmain<to, 4>(argc); // expected-note {{in instantiation of function template specialization 'tmain<int, 3>' requested here}} expected-note {{in instantiation of function template specialization 'tmain<int, 4>' requested here}}
 }
 

clang/test/OpenMP/target_update_to_messages.cpp

struct S8 {
   void foo() {
 #pragma omp target update to(*this) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
     {}
 #pragma omp target update to(*(this->ptr)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(*(this->S->i+this->S->p)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(*(this->S->i+this->S->s6[0].pp)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(*(a+this->ptr)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(*(*(this->ptr)+a+this->ptr)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
-#pragma omp target update to(*(this+this)) // expected-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}} expected-error {{invalid operands to binary expression ('S8 *' and 'S8 *')}}
+#pragma omp target update to(*(this+this)) // expected-error {{invalid operands to binary expression ('S8 *' and 'S8 *')}}
     {}
   }
 };
 
 S3 h;
 #pragma omp threadprivate(h) // expected-note 2 {{defined as threadprivate or thread local}}
 
 typedef int from;

 #pragma omp target update to(**(BB+y)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(*(m+*offset)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(**(*offset+BB)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(**(y+BB)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(*(*offset+m)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(**(*offset+BB+*m)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(**(*(*(&offset))+BB+*m)) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
 #pragma omp target update to(*(x+*(y+*(**BB+BBB)+s7.i))) // le45-error {{expected expression containing only member accesses and/or array sections based on named variables}} le45-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
-#pragma omp target update to(*(m+(m))) // expected-error {{invalid operands to binary expression ('int *' and 'int *')}} expected-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
-#pragma omp target update to(*(1+y+y)) // expected-error {{indirection requires pointer operand ('int' invalid)}} expected-error {{expected at least one 'to' clause or 'from' clause specified to '#pragma omp target update'}}
+#pragma omp target update to(*(m+(m))) // expected-error {{invalid operands to binary expression ('int *' and 'int *')}}
+#pragma omp target update to(*(1+y+y)) // expected-error {{indirection requires pointer operand ('int' invalid)}}
   {}
   return tmain<int, 3>(argc)+tmain<from, 4>(argc); // expected-note {{in instantiation of function template specialization 'tmain<int, 3>' requested here}} expected-note {{in instantiation of function template specialization 'tmain<int, 4>' requested here}}
 }
 

clang/test/Parser/objcxx0x-lambda-expressions.mm

 // RUN: %clang_cc1 -fsyntax-only -verify -Wno-unused-value -Wno-c++1y-extensions -std=c++11 %s
 
 class C {
   id get(int);
 
   void f() {
     int foo, bar, baz;
 
     // fail to parse as a lambda introducer, so we get objc message parsing errors instead
     [foo,+] {}; // expected-error {{expected expression}}
 
     []; // expected-error {{expected body of lambda expression}}
     [=,foo+] {}; // expected-error {{expected ',' or ']' in lambda capture list}}
-    [&this] {}; // expected-error {{cannot take the address of an rvalue of type 'C *'}}
+    [&this] {}; // expected-error {{cannot take the address of an rvalue of type 'C *'}} \
+                // expected-error {{expected identifier}}
     [] {}; 
     [=] (int i) {}; 
     [&] (int) mutable -> void {}; 
     [foo,bar] () { return 3; }; 
     [=,&foo] () {}; 
     [this] () {}; 
 
     [foo(bar)] () {};
     [foo = bar] () {};
     [foo{bar}] () {};
     [foo = {bar}] () {}; // expected-error {{<initializer_list>}}
 
-    [foo(bar) baz] () {}; // expected-error {{called object type 'int' is not a function}}
+    [foo(bar) baz] () {}; // expected-error {{called object type 'int' is not a function}} \
+                          // expected-error {{expected ';'}}
     [foo(bar), baz] () {}; // ok
 
     [foo = bar baz]; // expected-warning {{receiver type 'int'}} expected-warning {{instance method '-baz'}}
 
     [get(bar) baz]; // expected-warning {{instance method '-baz'}}
     [get(bar), baz]; // expected-error {{expected body of lambda}}
 
     [foo = bar ++ baz]; // expected-warning {{receiver type 'int'}} expected-warning {{instance method '-baz'}}

clang/test/Parser/objcxx11-invalid-lambda.cpp

 // RUN: %clang_cc1 -fsyntax-only -verify -x objective-c++ -std=c++11 %s
 
-void foo() {  // expected-note {{to match this '{'}}
+void foo() {
   int bar;
   auto baz = [
-      bar(  // expected-note {{to match this '('}} expected-note {{to match this '('}}
+      bar(  // expected-note 2{{to match this '('}}\
+            // expected-warning {{captures are a C++14 extension}}
         foo_undeclared() // expected-error{{use of undeclared identifier 'foo_undeclared'}}
       /* ) */
-    ] () { };   // expected-error{{expected ')'}}
-}               // expected-error{{expected ')'}} expected-error {{expected ',' or ']'}} expected-error{{expected ';' at end of declaration}} expected-error{{expected '}'}}
+    ] () { };   // expected-error 2{{expected ')'}}
+}
 No newline at end of file

clang/test/SemaCXX/builtins.cpp

 // RUN: %clang_cc1 %s -fsyntax-only -verify -std=c++11 -fcxx-exceptions
 // RUN: %clang_cc1 %s -fsyntax-only -verify -std=c++1z -fcxx-exceptions
 typedef const struct __CFString * CFStringRef;
 #define CFSTR __builtin___CFStringMakeConstantString
 
 void f() {
   (void)CFStringRef(CFSTR("Hello"));
 }
 
 void a() { __builtin_va_list x, y; ::__builtin_va_copy(x, y); }
 
 // <rdar://problem/10063539>
 template<int (*Compare)(const char *s1, const char *s2)>
 int equal(const char *s1, const char *s2) {
   return Compare(s1, s2) == 0;
 }
-// FIXME: Our error recovery here sucks
-template int equal<&__builtin_strcmp>(const char*, const char*); // expected-error {{builtin functions must be directly called}} expected-error {{expected unqualified-id}} expected-error {{expected ')'}} expected-note {{to match this '('}}
+
+template int equal<&__builtin_strcmp>(const char*, const char*); // expected-error {{builtin functions must be directly called}}
 
 // PR13195
 void f2() {
   __builtin_isnan; // expected-error {{builtin functions must be directly called}}
 }
 
 // pr14895
 typedef __typeof(sizeof(int)) size_t;

clang/test/SemaCXX/cast-conversion.cpp

-// RUN: %clang_cc1 -fsyntax-only -triple x86_64-unknown-unknown -verify %s -std=c++11
+// RUN: %clang_cc1 -fsyntax-only -triple x86_64-unknown-unknown -verify %s -std=c++11 -Wno-unused
 
 struct R {
   R(int);
 };
 
 struct A {
   A(R);
 };

clang/test/SemaCXX/cxx1z-copy-omission.cpp

-// RUN: %clang_cc1 -std=c++1z -verify %s
+// RUN: %clang_cc1 -std=c++1z -verify -Wno-unused %s
 
 struct Noncopyable {
   Noncopyable();
   Noncopyable(const Noncopyable &) = delete; // expected-note 1+{{deleted}} expected-note 1+ {{not viable}}
   virtual ~Noncopyable();
 };
 struct Derived : Noncopyable {};
 struct NoncopyableAggr { // expected-note 3{{candidate}}
void test_expressions(bool b) {
   make_incomplete().*(int Incomplete::*)nullptr; // expected-error {{incomplete}}
   dynamic_cast<Incomplete&&>(make_incomplete()); // expected-error {{incomplete}}
   const_cast<Incomplete&&>(make_incomplete()); // expected-error {{incomplete}}
 
   sizeof(Indestructible{}); // expected-error {{deleted}}
   sizeof(make_indestructible()); // expected-error {{deleted}}
   sizeof(make_incomplete()); // expected-error {{incomplete}}
   typeid(Indestructible{}); // expected-error {{deleted}}
-  typeid(make_indestructible()); // expected-error {{deleted}}
-  typeid(make_incomplete()); // expected-error {{incomplete}}
+  typeid(make_indestructible()); // expected-error {{deleted}} \
+                                 // expected-error {{need to include <typeinfo>}}
+  typeid(make_incomplete()); // expected-error {{incomplete}} \
+                             // expected-error {{need to include <typeinfo>}}
 
   // FIXME: The first two cases here are now also valid in C++17 onwards.
   using I = decltype(Indestructible()); // expected-error {{deleted}}
   using I = decltype(Indestructible{}); // expected-error {{deleted}}
   using I = decltype(make_indestructible());
   using J = decltype(make_incomplete());
 
   Noncopyable cond1 = b ? Noncopyable() : make();

clang/test/SemaCXX/decltype-crash.cpp

 // RUN: %clang_cc1 -fsyntax-only -verify -Wc++11-compat -std=c++98 %s
 
 int& a();
 
 void f() {
-  decltype(a()) c; // expected-warning {{'decltype' is a keyword in C++11}} expected-error {{use of undeclared identifier 'decltype'}}
+  decltype(a()) c; // expected-warning {{'decltype' is a keyword in C++11}} \
+                   // expected-error {{use of undeclared identifier 'decltype'}} \
+                   // expected-error {{expected ';' after expression}} \
+                   // expected-error {{use of undeclared identifier 'c'}}
 }

clang/test/SemaCXX/varargs.cpp

void no_params(...) {
   int a;
   __builtin_va_start(ap, a); // expected-warning {{second argument to 'va_start' is not the last named parameter}}
 }
 
 // Reject this. The __builtin_va_start would execute in Foo's non-variadic
 // default ctor.
 void record_context(int a, ...) {
   struct Foo {
-    // expected-error@+1 {{'va_start' cannot be used outside a function}}
+    // expected-error@+2 {{'va_start' cannot be used outside a function}}
+    // expected-error@+1 {{default argument references parameter 'a'}}
     void meth(int a, int b = (__builtin_va_start(ap, a), 0)) {}
   };
 }
 
 #if __cplusplus >= 201103L
 // We used to have bugs identifying the correct enclosing function scope in a
 // lambda.
 

clang/test/SemaOpenCLCXX/address-space-references.cl

 // RUN: %clang_cc1 %s -triple spir-unknown-unknown -cl-std=clc++ -pedantic -verify -fsyntax-only
 
 __global const int& f(__global float &ref) {
   return ref; // expected-error{{reference of type 'const __global int &' cannot bind to a temporary object because of address space mismatch}}
 }
 
 int bar(const __global unsigned int &i); // expected-note{{passing argument to parameter 'i' here}}
 //FIXME: With the overload below the call should be resolved
 // successfully. However, current overload resolution logic
 // can't detect this case and therefore fails.
 int bar(const unsigned int &i);
 
 void foo() {
-  bar(1) // expected-error{{binding reference of type 'const __global unsigned int' to value of type 'int' changes address space}}
+  bar(1); // expected-error{{binding reference of type 'const __global unsigned int' to value of type 'int' changes address space}}
 }
 
 // Test addr space conversion with nested pointers
 
 extern void nestptr(int *&); // expected-note {{candidate function not viable: no known conversion from '__global int *__private' to '__generic int *__generic &__private' for 1st argument}}
 extern void nestptr_const(int * const &); // expected-note {{candidate function not viable: cannot pass pointer to address space '__constant' as a pointer to address space '__generic' in 1st argument}}
 int test_nestptr(__global int *glob, __constant int *cons, int* gen) {
   nestptr(glob); // expected-error{{no matching function for call to 'nestptr'}}
   // Addr space conversion first occurs on a temporary.
   nestptr_const(glob);
   // No legal conversion between disjoint addr spaces.
   nestptr_const(cons); // expected-error{{no matching function for call to 'nestptr_const'}}
   return *(*cons ? glob : gen);
 }

clang/test/SemaTemplate/instantiate-init.cpp

namespace PR7985 {
 
   template<>
   const Data<float*> Description<float*>::data[];
 
   void test() {
     integral_c<1> ic1 = array_lengthof(Description<int>::data);
     (void)sizeof(array_lengthof(Description<float>::data));
 
-    sizeof(array_lengthof( // expected-error{{no matching function for call to 'array_lengthof'}}
+    (void)sizeof(array_lengthof( // expected-error{{no matching function for call to 'array_lengthof'}}
                           Description<int*>::data // expected-note{{in instantiation of static data member 'PR7985::Description<int *>::data' requested here}}
                           ));
 
     array_lengthof(Description<float*>::data); // expected-error{{no matching function for call to 'array_lengthof'}}
   }
 }
 
 namespace PR13064 {

clang/unittests/Sema/CodeCompleteTest.cpp

TEST(PreferredTypeTest, FunctionArguments) {
   EXPECT_THAT(collectPreferredTypes(Code), Each("vector<int>"));
 }
 
 TEST(PreferredTypeTest, NoCrashOnInvalidTypes) {
   StringRef Code = R"cpp(
     auto x = decltype(&1)(^);
     auto y = new decltype(&1)(^);
   )cpp";
-  EXPECT_THAT(collectPreferredTypes(Code), Each("NULL TYPE"));
+  EXPECT_THAT(collectPreferredTypes(Code),
+              Each("decltype(<recovery-expr>(1))"));
 }
 } // namespace