@deprecated for properties of merged Interfaces

[htho]

TypeScript Version: 4.1.0-dev.20200903

Search Terms: deprecated, interface, merge

Code

interface O {
	old: "old";
	new: "new";
}
interface O {
	/** @deprecated */
	old: "old";
}

const o: O = {} as any;

const a = o.old;

Expected behavior:
o.old should be marked as deprecated

Actual behavior:
o.old is not marked as deprecated

Playground Link: https://www.typescriptlang.org/play?ts=4.1.0-dev.20200903&ssl=6&ssc=20&pln=6&pc=2#code/JYOwLgpgTgZghgYwgAgPLIN4CgCQB7AGwBMAuZAIkKPIG5cQIB3M8hx2rAXy1ElkRTpsOAPQAqMcgACRCAAcoEBHEhFkYkbiosqHblgR4QAZzDI8ZdAF5MnZHGP2QATzoGjp+8ht4AdFRogA

Related Issues: none as far as I know.

[htho]

UPDATE: I found out, that the issue does not occur with functions. I updated the issues title to reflect that.

TypeScript Version: 4.1.0-dev.20200903

Search Terms: deprecated, interface, merge, properties

Code

interface O {
	oldProp: "old";
	newProp: "new";
	oldFunc(): "old";
	newFunc(): "new";
}
interface O {
	/** @deprecated */
	oldProp: "old";
	/** @deprecated */
	oldFunc(): "old";
}

const o: O = {} as any;

const a = o.oldProp; // should be marked as deprecated, but isn't
const b = o.oldFunc(); // properly marked as deprecated

Expected behavior:
o.oldProp and o.oldFunc() should be marked as deprecated.

Actual behavior:
Only o.oldFunc() is marked as deprecated. o.old is not marked as deprecated.

Playground Link: https://www.typescriptlang.org/play?ts=4.1.0-dev.20200903#code/JYOwLgpgTgZghgYwgAgPLIN4CgCQB7AGwBMAFKPABwC5kAiQo2gblxAgHczKba33ncDAGIBXEAgAUASh4MBOPqPHSefAQF8soSLEQp02HAHoAVCeQABIhApQICOJCLITRwcS7U6clsbOXrW3tHCGdXdyIlSRlvYg0sLAQ8EABnMGQ8GnQAXkx1ZDgUgpAATxZE5LSC5Fy8ADoGTxYk1PSAIxqMhuIo6SYgA

Related Issues: none as far as I know.

[Kingwl]

Seems caused by we check valueDeclaration and the NodeFlag of it when touch property access.
But in this case, valueDeclaration has assigned as first declaration.
As the result, if you mark deprecated at first declaration, that will work well.

/cc: @sandersn We need symbol flags perhaps.

[piotrzarycki]

can i take this?

[AnyhowStep]

Would something like this make sense?

        function getCombinedDeclarationNodeFlagsFromSymbol(s: Symbol): NodeFlags {
            if (!s.declarations) {
                return 0;
            }
            let flags = 0;
            for (const declaration of s.declarations) {
                flags |= getCombinedNodeFlags(declaration);
            }
            return flags;
        }

And then we have getCombinedDeclarationNodeFlagsFromSymbol(prop) & NodeFlags.Deprecated

---

This would also need to be fixed,

[k8w]

This problem is still existed in v4.8.4, is there any plan to fix it?