Throw Expressions not working for Boolean expressions?

Question

Throw Expressions work in this case:

string myStr;

public MyObj( string myStr ) =>
    this.myStr = myStr ?? throw new ArgumentNullException( "myStr" );

But why doesn't this compile too?

bool isRunning;

public void Run() =>
    isRunning = !isRunning || throw new InvalidOperationException( "Already running" );

Answer 1

From the original proposal on github:

A throw expression is permitted in only the following syntactic contexts:

• As the second or third operand of a ternary conditional operator ?:
• As the second operand of a null coalescing operator ??
• As the body of an expression-bodied lambda or method.

These are the only three cases where throw expressions can be used. Thus your use of a throw in a boolean expression isn't covered and isn't valid syntax.