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False negatives and false positives for "Object is possibly 'null'" warning in typescript@next with "complex" if #10198
Description
TypeScript Version: 2.1.0-dev.20160807
Code
class Nested {
data: string;
}
class Foo {
bar: Nested | null = null;
baz: number = 1;
get data(): null | string {
if (this.bar === null || this.baz !== 1) {
return null;
} else {
return this.bar.data;
// ^~~~~ Object is possibly 'null'. (BUT IT CAN'T BE NULL.)
}
}
}Expected behavior:
No error.
Actual behavior:
An error.
Details:
This failure must be new. I think I installed typescript@next last week and had no error. I installed it today and it throws an error now.
If a you remove the second if-branch (this.baz !== 1) it works.
This also throws:
get data(): null | string {
if (this.bar === null) {
return null;
} else if (this.baz !== 1) {
return null;
} else {
return this.bar.data;
// ^~~~~ Object is possibly 'null'. (BUT IT CAN'T BE NULL.)
}
}
This works:
get data(): null | string {
if (this.baz !== 1) {
return null;
} else if (this.bar === null) {
return null;
} else {
return this.bar.data;
}
}
(!) On the other hand: This works, but could be wrong so it should throw an error!
get data(): null | string {
if (this.baz !== 1 || this.bar === null) {
return null;
} else {
return this.bar.data;
}
}
Activity
[-]Incorrect "Object is possibly 'null'" warning in typescript@next with "complex" if [/-][+]False negatives and false positives for "Object is possibly 'null'" warning in typescript@next with "complex" if [/+]yortus commentedon Aug 8, 2016
This also works:
ahejlsberg commentedon Aug 8, 2016
Duplicate of #10169, fix available in #10188.