[Clang] [C++26] Expansion Statements (Part 5: Iterating Expansion Statements)

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -165,6 +165,8 @@ def err_ice_too_large : Error<
 def err_expr_not_string_literal : Error<"expression is not a string literal">;
 def note_constexpr_assert_failed : Note<
   "assertion failed during evaluation of constant expression">;
+def err_expansion_size_expr_not_ice : Error<
+  "expansion size is not a constant expression">;
 
 // Semantic analysis of constant literals.
 def ext_predef_outside_function : Warning<
@@ -3698,6 +3700,13 @@ def err_conflicting_codeseg_attribute : Error<
 def warn_duplicate_codeseg_attribute : Warning<
   "duplicate code segment specifiers">, InGroup<Section>;
 
+def err_expansion_stmt_vla : Error<
+  "cannot expand variable length array type %0">;
+def err_expansion_stmt_incomplete : Error<
+  "cannot expand expression of incomplete type %0">;
+def err_expansion_stmt_lambda : Error<
+  "cannot expand lambda closure type">;
+
 def err_attribute_patchable_function_entry_invalid_section
     : Error<"section argument to 'patchable_function_entry' attribute is not "
             "valid for this target: %0">;

clang/include/clang/Sema/Sema.h

@@ -15704,6 +15704,12 @@ class Sema final : public SemaBase {
                                                      SourceLocation ColonLoc,
                                                      SourceLocation RParenLoc);
 
+  StmtResult BuildNonEnumeratingCXXExpansionStmtPattern(
+      CXXExpansionStmtDecl *ESD, Stmt *Init, DeclStmt *ExpansionVarStmt,
+      Expr *ExpansionInitializer, SourceLocation LParenLoc,
+      SourceLocation ColonLoc, SourceLocation RParenLoc,
+      ArrayRef<MaterializeTemporaryExpr *> LifetimeExtendTemps = {});
+
   ExprResult BuildCXXExpansionSelectExpr(InitListExpr *Range, Expr *Idx);
 
   std::optional<uint64_t>