Move var declaration to in-place for spread in expressions

[nathancahill]

When a spread is in a "naked" expression, the added (ref will become a function call of the previous statement, unless a ; is added before it. This fix moves the declaration of the ref variable to immediately before the expression. See the tests for how code is now generated.

[adrianheine]

This check is not enough if the CallExpression is not the expression of the ExpressionStatement, like this:

const foo = { bar: [] }
const baz = true ? [1,2,3] : []
foo.bar.push(...baz)()

[nathancahill]

Good point. A better check here would be if the start of parent is also the start of the statement.

[adrianheine]

I tried the following a few days ago:

                                        } else {
                                                context = this.findScope(true).createDeclaration('ref');
                                                const callExpression = this.callee.object;
-                                           code.prependRight(callExpression.start, `(${context} = `);
+                                         const statement = this.findNearest(/Statement/);
+                                         code.prependRight(callExpression.start, (statement.start === callExpression.start ? ';' : '') + `(${context} = `);
                                                code.appendLeft(callExpression.end, `)`);
                                        }

That broke the following test, though:

function foo (x) {
        if ( x )
          return ref => (bar || baz).Test( ref, ...arguments );
      }

[adrianheine]

@nathancahill Do you still want to work on this? I would like to cut a release in the next days.

[nathancahill]

I'll take another swing at it this afternoon. I think your approach with a special case for statements without a body (like arrow functions) will work.