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Clarify some points in Member Access design #3177

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merged 4 commits into from
Sep 6, 2023
Merged

Clarify some points in Member Access design #3177

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2103fd4
Clarify some points in Member Access design
josh11b Aug 31, 2023
36b979e
Update with decision from #2200.
josh11b Aug 31, 2023
79797bd
Checkpoint progress.
josh11b Aug 31, 2023
631cd7f
Add example based on suggestion
josh11b Aug 31, 2023
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18 changes: 9 additions & 9 deletions docs/design/expressions/member_access.md
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
- [Values](#values)
- [Facet binding](#facet-binding)
- [Compile-time bindings](#compile-time-bindings)
- [Lookup ambiguity](#lookup-ambiguity)
- [Lookup ambiguity](#lookup-ambiguity)
- [`impl` lookup](#impl-lookup)
- [`impl` lookup for simple member access](#impl-lookup-for-simple-member-access)
- [`impl` lookup for compound member access](#impl-lookup-for-compound-member-access)
Expand Down Expand Up @@ -254,10 +254,9 @@ fn PrintPointTwice() {

### Facet binding

If any of the above lookups would search for members of a
[facet binding](/docs/design/generics/terminology.md#facet-binding) `T:! C`, it
searches the facet `T as C` instead, treating the facet binding as an
[archetype](/docs/design/generics/terminology.md#archetype).
A search for members of a facet binding `T:! C` treats the facet binding as an
[archetype](/docs/design/generics/terminology.md#archetype), and finds members
of the facet `T` of facet type `C`.

For example:

Expand Down Expand Up @@ -301,7 +300,8 @@ interface Renderable {
fn Draw[self: Self]();
}
fn DrawChecked[T:! Renderable](c: T) {
// `Draw` resolves to `Renderable.Draw`.
// `Draw` resolves to `(T as Renderable).Draw` or
// `T.(Renderable.Draw)`.
c.Draw();
}

Expand Down Expand Up @@ -358,7 +358,7 @@ bindings that are in scope are unknown. Unlike for a template binding, the
actual value of a symbolic binding never affects the result of member
resolution.

##### Lookup ambiguity
#### Lookup ambiguity

Multiple lookups can be performed when resolving a member access expression with
a [template binding](#compile-time-bindings). We resolve this the same way as
Expand All @@ -378,8 +378,8 @@ interface Renderable {
}

fn DrawTemplate2[template T:! Renderable](c: T) {
// Member lookup finds `Renderable.Draw` and the `Draw`
// member of the actual deduced value of `T`, if any.
// Member lookup finds `(T as Renderable).Draw` and the
// `Draw` member of the actual deduced value of `T`, if any.
c.Draw();
}

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