[AST] Fix recovery-expr crash on invalid aligned attr.

Summary:
crash stack:

```
lang: tools/clang/include/clang/AST/AttrImpl.inc:1490: unsigned int clang::AlignedAttr::getAlignment(clang::ASTContext &) const: Assertion `!isAlignmentDependent()' failed.
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: ./bin/clang -cc1 -std=c++1y -ast-dump -frecovery-ast -fcxx-exceptions /tmp/t4.cpp
1.      /tmp/t4.cpp:3:31: current parser token ';'
 #0 0x0000000002530cff llvm::sys::PrintStackTrace(llvm::raw_ostream&) llvm-project/llvm/lib/Support/Unix/Signals.inc:564:13
 #1 0x000000000252ee30 llvm::sys::RunSignalHandlers() llvm-project/llvm/lib/Support/Signals.cpp:69:18
 #2 0x000000000253126c SignalHandler(int) llvm-project/llvm/lib/Support/Unix/Signals.inc:396:3
 #3 0x00007f86964d0520 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x13520)
 #4 0x00007f8695f9ff61 raise /build/glibc-oCLvUT/glibc-2.29/signal/../sysdeps/unix/sysv/linux/raise.c:51:1
 #5 0x00007f8695f8b535 abort /build/glibc-oCLvUT/glibc-2.29/stdlib/abort.c:81:7
 #6 0x00007f8695f8b40f _nl_load_domain /build/glibc-oCLvUT/glibc-2.29/intl/loadmsgcat.c:1177:9
 #7 0x00007f8695f98b92 (/lib/x86_64-linux-gnu/libc.so.6+0x32b92)
 #8 0x0000000004503d9f llvm::APInt::getZExtValue() const llvm-project/llvm/include/llvm/ADT/APInt.h:1623:5
 #9 0x0000000004503d9f clang::AlignedAttr::getAlignment(clang::ASTContext&) const llvm-project/build/tools/clang/include/clang/AST/AttrImpl.inc:1492:0
```

Reviewers: sammccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78085

clang/lib/AST/ComputeDependence.cpp

@@ -71,8 +71,10 @@ ExprDependence clang::computeDependence(UnaryExprOrTypeTraitExpr *E) {
   if (!D)
     return Deps;
   for (const auto *I : D->specific_attrs<AlignedAttr>()) {
+    if (I->isAlignmentErrorDependent())
+      Deps |= ExprDependence::Error;
     if (I->isAlignmentDependent())
-      return Deps | ExprDependence::ValueInstantiation;
+      Deps |= ExprDependence::ValueInstantiation;
   }
   return Deps;
 }

clang/lib/AST/DeclBase.cpp

@@ -396,8 +396,10 @@ unsigned Decl::getMaxAlignment() const {
   const AttrVec &V = getAttrs();
   ASTContext &Ctx = getASTContext();
   specific_attr_iterator<AlignedAttr> I(V.begin()), E(V.end());
-  for (; I != E; ++I)
-    Align = std::max(Align, I->getAlignment(Ctx));
+  for (; I != E; ++I) {
+    if (!I->isAlignmentErrorDependent())
+      Align = std::max(Align, I->getAlignment(Ctx));
+  }
   return Align;
 }
 

clang/test/AST/ast-dump-recovery.cpp

@@ -97,4 +97,9 @@ struct Foo {} foo;
 void test(int x) {
   foo.abc;
   foo->func(x);
-}
+}
+
+// CHECK:     |-AlignedAttr {{.*}} alignas
+// CHECK-NEXT:| `-RecoveryExpr {{.*}} contains-errors
+// CHECK-NEXT:|   `-UnresolvedLookupExpr {{.*}} 'invalid'
+struct alignas(invalid()) Aligned {};

clang/test/SemaCXX/invalid-aligned-attr.cpp

@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -frecovery-ast -verify %s
+// RUN: %clang_cc1 -verify %s
+
+struct alignas(invalid()) Foo {}; // expected-error {{use of undeclared identifier}}
+
+constexpr int k = alignof(Foo);

clang/utils/TableGen/ClangAttrEmitter.cpp

@@ -481,6 +481,7 @@ namespace {
 
     void writeAccessors(raw_ostream &OS) const override {
       OS << "  bool is" << getUpperName() << "Dependent() const;\n";
+      OS << "  bool is" << getUpperName() << "ErrorDependent() const;\n";
 
       OS << "  unsigned get" << getUpperName() << "(ASTContext &Ctx) const;\n";
 
@@ -511,6 +512,15 @@ namespace {
          << "Type->getType()->isDependentType();\n";
       OS << "}\n";
 
+      OS << "bool " << getAttrName() << "Attr::is" << getUpperName()
+         << "ErrorDependent() const {\n";
+      OS << "  if (is" << getLowerName() << "Expr)\n";
+      OS << "    return " << getLowerName() << "Expr && " << getLowerName()
+         << "Expr->containsErrors();\n";
+      OS << "  return " << getLowerName()
+         << "Type->getType()->containsErrors();\n";
+      OS << "}\n";
+
       // FIXME: Do not do the calculation here
       // FIXME: Handle types correctly
       // A null pointer means maximum alignment