From 56e5da5aa573119e765da47e1b1d7d7b98710647 Mon Sep 17 00:00:00 2001
From: "Igor V. Kovalenko" <igor.v.kovalenko@gmail.com>
Date: Sun, 5 Mar 2023 15:12:42 +0300
Subject: [PATCH] Allow expansion with typeids in fold expression

---
 .../tests/ast2/cxx17/FoldExpressionTests.java | 36 +++++++++++++++++++
 .../dom/parser/cpp/CPPASTFoldExpression.java  | 19 ++++++++++
 2 files changed, 55 insertions(+)

diff --git a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/FoldExpressionTests.java b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/FoldExpressionTests.java
index 35b2c6d6ff0..cdefebc3811 100644
--- a/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/FoldExpressionTests.java
+++ b/core/org.eclipse.cdt.core.tests/parser/org/eclipse/cdt/core/parser/tests/ast2/cxx17/FoldExpressionTests.java
@@ -186,4 +186,40 @@ public class FoldExpressionTests extends AST2CPPTestBase {
 		IASTFunctionDefinition fdef = (IASTFunctionDefinition) tdef.getDeclaration();
 		IASTProblemExpression e1 = getExpressionOfStatement(fdef, 0);
 	}
+
+	//  template <typename T> struct predicate {
+	//    static constexpr bool evaluated = true;
+	//  };
+	//
+	//  template<bool arg> struct condition {
+	//    static constexpr bool value = arg;
+	//  };
+	//
+	//  template<typename... TP>
+	//  struct fold_condition {
+	//    static constexpr bool value = condition<(predicate<TP>::evaluated && ...)>::value;
+	//  };
+	//
+	//  constexpr bool result = fold_condition<int, double>::value;
+	public void testFoldExpressionInClassTemplateArguments() throws Exception {
+		BindingAssertionHelper helper = getAssertionHelper();
+		helper.assertVariableValue("result", 1);
+	}
+
+	//  template<typename T1> constexpr bool predicate = true;
+	//
+	//  template<bool arg> struct condition {
+	//    static constexpr bool value = arg;
+	//  };
+	//
+	//  template<typename... TP>
+	//  struct fold_condition {
+	//    static constexpr bool value = condition<(predicate<TP> && ...)>::value;
+	//  };
+	//
+	//  constexpr bool result = fold_condition<int, double>::value;
+	public void testFoldExpressionInVariableTemplateArguments() throws Exception {
+		BindingAssertionHelper helper = getAssertionHelper();
+		helper.assertVariableValue("result", 1);
+	}
 }
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTFoldExpression.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTFoldExpression.java
index 4a88b91491f..851db7e366b 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTFoldExpression.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/dom/parser/cpp/CPPASTFoldExpression.java
@@ -19,14 +19,17 @@ import org.eclipse.cdt.core.dom.ast.ASTVisitor;
 import org.eclipse.cdt.core.dom.ast.IASTExpression;
 import org.eclipse.cdt.core.dom.ast.IASTImplicitDestructorName;
 import org.eclipse.cdt.core.dom.ast.IASTNode;
+import org.eclipse.cdt.core.dom.ast.IASTTypeId;
 import org.eclipse.cdt.core.dom.ast.IType;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTExpression;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTFoldExpression;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTPackExpansionExpression;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPParameterPackType;
+import org.eclipse.cdt.core.dom.ast.cpp.ICPPTemplateParameter;
 import org.eclipse.cdt.internal.core.dom.parser.ASTNode;
 import org.eclipse.cdt.internal.core.dom.parser.IASTAmbiguityParent;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.CPPEvaluation;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.CPPVisitor;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.DestructorCallCollector;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.EvalFixed;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.semantics.EvalFoldExpression;
@@ -103,6 +106,7 @@ public class CPPASTFoldExpression extends ASTNode implements ICPPASTFoldExpressi
 		public UnexpandedParameterPackCounter() {
 			super(false);
 			shouldVisitExpressions = true;
+			shouldVisitTypeIds = true;
 			count = 0;
 		}
 
@@ -122,6 +126,21 @@ public class CPPASTFoldExpression extends ASTNode implements ICPPASTFoldExpressi
 			}
 			return PROCESS_CONTINUE;
 		}
+
+		@Override
+		public int visit(IASTTypeId typeId) {
+			IType type = CPPVisitor.createType(typeId);
+			if (type instanceof ICPPTemplateParameter templateParameter) {
+				if (templateParameter.isParameterPack()) {
+					++count;
+				} else {
+					boolean notParameterPack = true;
+				}
+			} else {
+				boolean notTemplateParameter = true;
+			}
+			return PROCESS_CONTINUE;
+		}
 	}
 
 	private int countUnexpandedParameterPacks(IASTExpression e) {