fix(classes): defer NEW for DECLARE without a parameterless constructor

A plain DECLARE, field or array element now calls NEW only when the class
has a parameterless one; otherwise the zeroed object waits for
x <- NEW C(...), as in guide section 10.2. DECLARE with parentheses still
requires a matching constructor.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

2 files changed, 13 insertions, 3 deletions

diff --git a/lib/CodeGen/ConstructorGen.cc b/lib/CodeGen/ConstructorGen.cc
index 8ca0258..286435e 100644
--- a/lib/CodeGen/ConstructorGen.cc
+++ b/lib/CodeGen/ConstructorGen.cc
@@ -114,8 +114,16 @@ bool CodeGen::emitConstruct(const std::string &TypeName, Value *Addr,
     return true;
 }
 
+// Guide 10.2 creation pattern: a plain DECLARE only runs NEW when the class has
+// a parameterless one; otherwise the object stays zeroed (fields constructed)
+// and a later `x <- NEW C(...)` binds it.
 bool CodeGen::emitDefaultConstruct(const std::string &TypeName, Value *Addr, int Line) {
-    return emitConstruct(TypeName, Addr, {}, Line);
+    const TypeInfo *Info = resolveType(TypeName);
+    if (!Info) return false;
+    for (const FuncSig *Sig : FuncGen->getOverloads(TypeName + ".NEW"))
+        if (Sig->Params.empty()) return emitConstruct(TypeName, Addr, {}, Line);
+    SaveAndRestore<int> Location(DiagnosticLine, Line);
+    return !Info->asRecord() || emitFieldDefaults(Info, Addr, Line);
 }
 
 // Default-constructs, in declaration order, each field of the record at Addr
diff --git a/lib/CodeGen/ValueTypeGen.cc b/lib/CodeGen/ValueTypeGen.cc
index e73b189..af32d74 100644
--- a/lib/CodeGen/ValueTypeGen.cc
+++ b/lib/CodeGen/ValueTypeGen.cc
@@ -262,6 +262,8 @@ void CodeGen::emitDeclareStmt(DeclareStmtAST *Stmt) {
         reportError("Constructor arguments require a class type");
         return;
     }
-    if (emitConstruct(Info->Name, Alloca, Stmt->getArgs(), Stmt->getLine()))
-        activateStackObject(Lifetime);
+    bool Constructed = Stmt->hasParens()
+        ? emitConstruct(Info->Name, Alloca, Stmt->getArgs(), Stmt->getLine())
+        : emitDefaultConstruct(Info->Name, Alloca, Stmt->getLine());
+    if (Constructed) activateStackObject(Lifetime);
 }