[clang] [Clang] Instantiate functions from constant evaluation. (PR #205557)

[Shafik Yaghmour via cfe-commits]

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@@ -22210,59 +22269,126 @@ bool Expr::EvaluateAsInitializer(const ASTContext &Ctx, const VarDecl *VD,
          CheckMemoryLeaks(Info);
 }
 
-bool VarDecl::evaluateDestruction(
-    SmallVectorImpl<PartialDiagnosticAt> &Notes) const {
+bool Expr::EvaluateAsInitializer(const ASTContext &Ctx, const VarDecl *VD,
+                                 Expr::EvalResult &EStatus,
+                                 bool IsConstantInitialization) const {
+  assert(!isValueDependent() &&
+         "Expression evaluator can't be called on a dependent expression.");
+  assert(VD && "Need a valid VarDecl");
+
+  llvm::TimeTraceScope TimeScope("EvaluateAsInitializer", [&] {
+    std::string Name;
+    llvm::raw_string_ostream OS(Name);
+    VD->printQualifiedName(OS);
+    return Name;
+  });
+
+  EvalInfo Info(Ctx, /*Sema=*/nullptr, EStatus,
+                (IsConstantInitialization &&
+                 (Ctx.getLangOpts().CPlusPlus || Ctx.getLangOpts().C23))
+                    ? EvaluationMode::ConstantExpression
+                    : EvaluationMode::ConstantFold);
+  Info.setEvaluatingDecl(VD, EStatus.Val);
+  Info.InConstantContext = IsConstantInitialization;
+
+  return ::EvaluateInitializer(Ctx, Info, VD, this, EStatus,
+                               IsConstantInitialization);
+}
+
+bool Expr::EvaluateAsMandatedConstantInitializer(EvalResult &EStatus,
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shafik wrote:

There is more code duplicate here, this one is not as totally duplicated but it is pretty darn close. 

https://github.com/llvm/llvm-project/pull/205557