resolve default template parameters from parent containers

[chrisradek]

Meant to partially address #6745

The extends case still acts oddly (and may be fixed when #6699 is fixed).

This case still won't produce any output:

interface Resource<T> {
  read<U = T>(): U;
}

model Foo {
  type: "foo";
}

interface FooResource extends Resource<Foo> {}

Because even though all the Resource template parameters are provided in the extends, the operation in FooResource does not get instantiated. I'm not 100% convinced this case is a bug though.

[github-actions]

All changed packages have been documented.

• ✅ @typespec/compiler

Show changes

@typespec/compiler - fix ✏️

Fixes template argument resolution when a default template parameter value is resolved by a parent container (e.g. interface),> For example:,> tsp,> interface Resource<T> {,> read<U = T>(): U;,> },> ,> model Foo {,> type: "foo";,> },> ,> alias FooResource = Resource<Foo>;,> ,> op readFoo is FooResource.read;,> ,> The returnType for readFoo would be model Foo. Previously the returnType resolved to a TemplateParameter.

[timotheeguerin]

oops

[azure-sdk]

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension

[steverice]

Hey @chrisradek , thanks for the fix.

I still encounter the error with this case:

interface A<T = {}> {
  op foo<R = T, P = R>(params: P): R;
}
op MyOp is A.foo;

(playground)

I'd expect that since all of the parameters are defined (P == R == T == {}) this should resolve. But again the error:

Error: Encountered type TemplateParameter which we don't know how to emit.

[chrisradek]

@steverice Thanks for bringing that up! This was a scenario I had in mind but clearly missed - working on a fix!