[英]TypeChecker API: How do I find inferred type arguments to a function?
Is there any way to, given a CallExpression with inferred type arguments, find what those type arguments are?有没有办法,给定一个推断类型为 arguments 的 CallExpression,找到那些类型 arguments 是什么?
Example code:示例代码:
class SomeClass {
public someMethod<T>(arg: T): void { }
}
// What is the inferred type of T in this call?
someClass.someMethod(7);
It's easy enough to find type arguments that were explicitly assigned in the code, but I can't figure out how to find what was inferred.很容易找到在代码中明确分配的类型 arguments,但我无法弄清楚如何找到推断出的内容。
function inferTypeArguments(node: ts.CallExpression, typeChecker: ts.TypeChecker) {
node.typeArguments; // is empty
const signature = typeChecker.getResolvedSignature(node);
signature['typeArguments']; // is also empty
// This returns "<number>(arg: number): void"
// so I know that the typeChecker has the right information,
// but I would really like a ts.Type[]
typeChecker.signatureToString(signature, node, ts.TypeFormatFlags.WriteTypeArgumentsOfSignature)
}
I'll leave this question open in case someone finds a better way, but I did accomplish this by using some internal members of "Signature".如果有人找到更好的方法,我会保留这个问题,但我确实通过使用“签名”的一些内部成员来实现这一点。
type TypeMapper = (t: ts.TypeParameter) => ts.Type;
function inferTypeArguments(node: ts.CallExpression, typeChecker: ts.TypeChecker): ts.Type[] {
const signature = typeChecker.getResolvedSignature(node);
const targetParams: ts.TypeParameter[] = signature['target'] && signature['target'].typeParameters;
if (!targetParams) {
return [];
}
const mapper: TypeMapper = signature['mapper'];
return mapper
? targetParams.map(p => mapper(p))
: targetParams;
}
I'd been using Simon's code for a while in my transpiler... then 3.9 came along and broke it.我在我的转译器中使用 Simon 的代码已经有一段时间了……然后 3.9 出现并破坏了它。 I've done a preliminary attempt to get it working again.
我已经做了初步尝试让它再次工作。 Unfortunately, the mapper is an "internal" concern for typescript, so this will likely change again in the future
不幸的是,映射器是打字稿的“内部”问题,因此将来可能会再次发生变化
/* @internal - from typescript 3.9 codebase*/
const enum TypeMapKind {
Simple,
Array,
Function,
Composite,
Merged,
}
/* @internal - from typescript 3.9 codebase*/
type TypeMapper =
| { kind: TypeMapKind.Simple, source: ts.Type, target: ts.Type }
| { kind: TypeMapKind.Array, sources: readonly ts.Type[], targets: readonly ts.Type[] | undefined }
| { kind: TypeMapKind.Function, func: (t: ts.Type) => ts.Type }
| { kind: TypeMapKind.Composite | TypeMapKind.Merged, mapper1: TypeMapper, mapper2: TypeMapper };
/* basic application of the mapper - recursive for composite.*/
function typeMapper(mapper:TypeMapper, source: ts.Type): ts.Type {
switch(mapper.kind){
case TypeMapKind.Simple:
return mapper.target;
case TypeMapKind.Array:
throw Error("not implemented");
case TypeMapKind.Function:
return mapper.func(source);
case TypeMapKind.Composite:
case TypeMapKind.Merged:
return typeMapper(mapper.mapper2, source);
}
}
function inferTypeArguments(node: ts.CallExpression, typeChecker: ts.TypeChecker): ts.Type[] {
const signature:ts.Signature = typeChecker.getResolvedSignature(node);
const targetParams: ts.TypeParameter[] = signature['target'] && signature['target'].typeParameters;
if (!targetParams) {
return [];
}
if(signature['mapper'] == undefined)
return targetParams;
//typescript <= 3.8
if(typeof signature['mapper'] == "function")
return targetParams.map(p=>signature['mapper'](p));
//typescript >= 3.9....
return targetParams.map(p=> typeMapper(signature['mapper'] as TypeMapper, p));
}
Actually now it is '4.9.4', the latest ' getMappedType ' is so complicated that I just give up implement it by myself其实现在是'4.9.4',最新的' getMappedType '太复杂了,我放弃了自己实现
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