[AST] Fix a crash on invalid constexpr Ctorinitializer when building …

…RecoveryExpr.

Summary:
crash stack:

```

lang:  workspace/llvm-project/clang/lib/AST/ExprConstant.cpp:13704: bool EvaluateInPlace(clang::APValue &, (anonymous namespace)::EvalInfo &, const (anonymous namespace)::LValue &, const clang::Expr *, bool): Assertion `!E->isValueDependent()' failed.
 rust-lang#8  EvaluateInPlace(clang::APValue&, (anonymous namespace)::EvalInfo&, (anonymous namespace)::LValue const&, clang::Expr const*, bool)  workspace/llvm-project/clang/lib/AST/ExprConstant.cpp:0:0
 rust-lang#9  HandleConstructorCall(clang::Expr const*, (anonymous namespace)::LValue const&, clang::APValue*, clang::CXXConstructorDecl const*, (anonymous namespace)::EvalInfo&, clang::APValue&)  workspace/llvm-project/clang/lib/AST/ExprConstant.cpp:5779:57
rust-lang#10  HandleConstructorCall(clang::Expr const*, (anonymous namespace)::LValue const&, llvm::ArrayRef<clang::Expr const*>, clang::CXXConstructorDecl const*, (anonymous namespace)::EvalInfo&, clang::APValue&)  workspace/llvm-project/clang/lib/AST/ExprConstant.cpp:5819:10
rust-lang#11  clang::Expr::isPotentialConstantExpr(clang::FunctionDecl const*, llvm::SmallVectorImpl<std::pair<clang::SourceLocation, clang::PartialDiagnostic> >&) workspace/llvm-project/clang/lib/AST/ExprConstant.cpp:14746:5
rust-lang#12  CheckConstexprFunctionBody(clang::Sema&, clang::FunctionDecl const*, clang::Stmt*, clang::Sema::CheckConstexprKind)  workspace/llvm-project/clang/lib/Sema/SemaDeclCXX.cpp:2306:7
rust-lang#13  clang::Sema::CheckConstexprFunctionDefinition(clang::FunctionDecl const*, clang::Sema::CheckConstexprKind)  workspace/llvm-project/clang/lib/Sema/SemaDeclCXX.cpp:1766:0
rust-lang#14  clang::Sema::ActOnFinishFunctionBody(clang::Decl*, clang::Stmt*, bool)  workspace/llvm-project/clang/lib/Sema/SemaDecl.cpp:14357:9
rust-lang#15  clang::Parser::ParseFunctionStatementBody(clang::Decl*, clang::Parser::ParseScope&)  workspace/llvm-project/clang/lib/Parse/ParseStmt.cpp:2213:18
```

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: rsmith, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77041

clang/lib/AST/ExprConstant.cpp

@@ -4976,6 +4976,13 @@ static bool CheckConstexprFunction(EvalInfo &Info, SourceLocation CallLoc,
     return false;
   }
 
+  if (const auto *CtorDecl = dyn_cast_or_null<CXXConstructorDecl>(Definition)) {
+    for (const auto *InitExpr : CtorDecl->inits()) {
+      if (InitExpr->getInit() && InitExpr->getInit()->containsErrors())
+        return false;
+    }
+  }
+
   // Can we evaluate this function call?
   if (Definition && Definition->isConstexpr() && Body)
     return true;
@@ -14709,6 +14716,15 @@ bool Expr::isPotentialConstantExpr(const FunctionDecl *FD,
   if (FD->isDependentContext())
     return true;
 
+  // Bail out if a constexpr constructor has an initializer that contains an
+  // error. We deliberately don't produce a diagnostic, as we have produced a
+  // relevant diagnostic when parsing the error initializer.
+  if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(FD)) {
+    for (const auto *InitExpr : Ctor->inits()) {
+      if (InitExpr->getInit() && InitExpr->getInit()->containsErrors())
+        return false;
+    }
+  }
   Expr::EvalStatus Status;
   Status.Diag = &Diags;
 

clang/test/SemaCXX/invalid-constructor-init.cpp

@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -frecovery-ast -verify %s
+
+struct X {
+  int Y;
+  constexpr X() // expected-error {{constexpr constructor never produces}}
+      : Y(foo()) {} // expected-error {{use of undeclared identifier 'foo'}}
+};
+// no crash on evaluating the constexpr ctor.
+constexpr int Z = X().Y; // expected-error {{constexpr variable 'Z' must be initialized by a constant expression}}
+
+struct X2 {
+  int Y = foo();    // expected-error {{use of undeclared identifier 'foo'}} \
+                 // expected-note {{subexpression not valid in a constant expression}}
+  constexpr X2() {} // expected-error {{constexpr constructor never produces a constant expression}}
+};
+
+struct CycleDelegate {
+  int Y;
+  CycleDelegate(int)
+      : Y(foo()) {} // expected-error {{use of undeclared identifier 'foo'}}
+  // no bogus "delegation cycle" diagnostic
+  CycleDelegate(float) : CycleDelegate(1) {}
+};