Computing best common type fails with weird error message

[xirzec]

interface IParserTest {
    name: string;
    input: string;
    result: any[];
    context?: any;
    error?: string;
}

var parserTests: IParserTest[] = [

    {
        name: "multipleBindingsWithSomeInitializers2",
        input: "textContent:b; innerHtml:e f;",
        result: [
            { destination: ["textContent"], source: ["b"] },
            { destination: ["innerHtml"], source: ["e"], initializer: 2 }
        ],
        context: { f: 2 }
    },
    {
        name: "bindingWithNumberLiterals",
        input: 'foo[1].baz:a.b[3]',
        result: [
            { destination: ["foo", 1, "baz"], source: ["a", "b", 3] }
        ]
    },
    {
        name: "errorBinding1",
        input: "textContent:b:c",
        error: "Invalid binding:'textContent:b:c'. Expected to be '<destProp>:<sourceProp>;'. Unexpected token: colon, expected one of: identifier, semicolon, eof, at offset 13"
    },
    {
        name: "errorBinding2",
        input: "textContent:b c: innerHtml: d e",
        error: "Invalid binding:'textContent:b c: innerHtml: d e'. Expected to be '<destProp>:<sourceProp>;'. Unexpected token: colon, expected one of: identifier, semicolon, eof, at offset 14",
        context: { c: 1, e: 3 }
    }
];

Gives the following error:

Cannot convert '{}[]' to 'IParserTest[]':
    Types of property 'pop' of types '{}[]' and 'IParserTest[]' are incompatible:
        Call signatures of types '() => {}' and '() => IParserTest' are incompatible:
            Type '{}' is missing property 'name' from type 'IParserTest'.

[RyanCavanaugh]

It is factual that the type of the array is {}[] -- no one element is a supertype of the rest, and there are members that don't have the required result field.

This is sort of the best we can do given the type algorithms we have. There's no obvious algorithm that generates a human-friendly error.

[xirzec]

Somehow I didn't notice that result wasn't on all of them. I may have been staring at code too long this weekend. 🎢