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Error on excess spread arguments

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Make the *technically* correct construction illegal:

```ts
declare function f(n: number): void;
declare var ns: number[];
f(1, ...ns);
```

This call only makes sense if `ns = []`, but in that case, why pass
`ns` at all? Allowing this call masks other errors when functions are
refactored to have fewer parameters, or to stop using rest parameters:

```ts
declare function old(...ns: number[]): void;
declare function new(ns: number | number[]): void;
old(1, ...ns); // Fine!
new(1, ...ns); // Should error!
```

This change the error for excess spread arguments to be more
understandable:

"Expected 3 arguments, but got least 4".

Previously the error would have been
"Expected 3 argument, but got at least 3", which is, again, technically
correct, but not understandable.
This commit is contained in:
Nathan Shively-Sanders 2017-11-16 09:31:50 -08:00
parent d49491b3a7
commit 8657dc10a7
1 changed files with 7 additions and 4 deletions
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11
src/compiler/checker.ts
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@ -15790,10 +15790,10 @@ namespace ts {
return false;
}
// If spread arguments are present, check that they correspond to a rest parameter. If so, no
// further checking is necessary.
// If a spread argument is present, check that it corresponds to a rest parameter or at least that it's in the valid range.
if (spreadArgIndex >= 0) {
return isRestParameterIndex(signature, spreadArgIndex) || spreadArgIndex >= signature.minArgumentCount;
return isRestParameterIndex(signature, spreadArgIndex) ||
signature.minArgumentCount <= spreadArgIndex && spreadArgIndex < signature.parameters.length;
}
// Too many arguments implies incorrect arity.
@ -16501,7 +16501,10 @@ namespace ts {
const paramCount = hasRestParameter ? min :
min < max ? min + "-" + max :
min;
const argCount = args.length - (hasSpreadArgument ? 1 : 0);
let argCount = args.length;
if (argCount <= max && hasSpreadArgument) {
argCount--;
}
const error = hasRestParameter && hasSpreadArgument ? Diagnostics.Expected_at_least_0_arguments_but_got_a_minimum_of_1 :
hasRestParameter ? Diagnostics.Expected_at_least_0_arguments_but_got_1 :
hasSpreadArgument ? Diagnostics.Expected_0_arguments_but_got_a_minimum_of_1 :