A class with an empty expression-bodied property is still written with its closing brace, minus that member and everything after it (#164 again, since #178) #183

What happens

var cls = new ClassTemplate
{
    Name = "C",
    Members =
    {
        new FieldTemplate { Type = "int", Name = "f" },
        new PropertyTemplate { Type = "int", Name = "P", ExpressionBodyFactory = b => { } },
    },
};
cls.WriteTo(cb);

WriteTo throws InvalidOperationException ("…has an expression body whose callback wrote no expression…"). By then the buffer already holds:

class C
{
	int f;

}

That is a well-formed class that silently lacks P and every member and nested class after it. It is the situation #164 was about, which #169 fixed by validating every member before writing the class header.

Reproduced against main @ aa7ca53 on net10.0. The same thing happens one level up through SourceFileTemplate / AddClasses, and for accessor expressions (Getter = AccessorTemplate.Expression(b => { })).

Why

#178 added the empty-expression check in TemplateRendering.RenderExpression (CodeBlocker/Templates/TemplateRendering.cs:338-349). That runs from PropertyTemplate.WriteTo and from the accessor write path, not from Validate(). So ClassTemplate.Validate() (ClassTemplate.cs:105-118) passes. The member then throws inside WriteBodyTo's using Scope, and disposing that scope writes the closing }.

Why it matters

A generator that catches the exception and reports it gets a compilable file with members missing. One that writes the buffer anyway (for example, a source generator that adds whatever was produced) ships a type with a silently truncated API. #169 exists to prevent exactly this.

Suggested fix

Make the check part of validation. Either:

• have PropertyTemplate.Validate() and AccessorTemplate.Validate() render the expression and throw when it is empty, or
• render all member fragments before the class header is written.

Acceptance criteria

• In the repro, WriteTo throws and nothing is written to the CodeBlocker.
• A test like the Check a class's members before writing any of it [patch] #169 one, using an empty ExpressionBodyFactory and an empty AccessorTemplate.Expression, covers this.

Related: #176 is the same "half-written then closed" shape when a user BodyFactory throws. This issue is about a check the library itself makes, which belongs in Validate().