Add Self to the name scope for a class. (#3736)

Rather than just adding `Self` to the lexical scope, add it to the
class's name scope so that it is visible in later lexical scopes for the
same class -- in particular, for out-of-line definitions of members.
Also switch some tests in `check/testdata/class` over to making
idiomatic use of `Self` both inside a class and out-of-line, now that it
works more consistently.

Note that this does not permit using `Class.Self`, but only because we
don't yet support keyword names after `.` at all. If that changed, one
could use `Class.Self` to redundantly refer to `Class`. Whether we allow
that is left to a future decision.

toolchain/check/testdata/impl/fail_extend_impl_forall.carbon

@@ -78,6 +78,7 @@ class C {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%C
 // CHECK:STDOUT:   has_error
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/impl/fail_extend_impl_type_as.carbon

@@ -73,6 +73,7 @@ class E {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%C
 // CHECK:STDOUT:   has_error
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -83,6 +84,7 @@ class E {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%D
 // CHECK:STDOUT:   extend name_scope1
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
@@ -93,6 +95,7 @@ class E {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%E
 // CHECK:STDOUT:   extend name_scope1
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/impl/fail_extend_non_interface.carbon

@@ -31,6 +31,7 @@ class C {
 // CHECK:STDOUT:   impl_decl @impl {}
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%C
 // CHECK:STDOUT:   has_error
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/impl/fail_extend_partially_defined_interface.carbon

@@ -47,6 +47,7 @@ interface I {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%C
 // CHECK:STDOUT:   has_error
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/impl/fail_extend_undefined_interface.carbon

@@ -43,6 +43,7 @@ class C {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%C
 // CHECK:STDOUT:   has_error
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/impl/fail_todo_extend_impl.carbon

@@ -76,6 +76,7 @@ fn G(c: C) {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:
 // CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%C
 // CHECK:STDOUT:   extend name_scope1
 // CHECK:STDOUT: }
 // CHECK:STDOUT:

toolchain/check/testdata/impl/impl_as.carbon

@@ -53,6 +53,9 @@ class C {
 // CHECK:STDOUT:   impl_decl @impl {
 // CHECK:STDOUT:     %Simple.ref: type = name_ref Simple, file.%Simple.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%C
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: fn @F.1();

toolchain/check/testdata/impl/redeclaration.carbon

@@ -48,5 +48,8 @@ impl i32 as I {}
 // CHECK:STDOUT:   impl_decl @impl {
 // CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [template = constants.%.1]
 // CHECK:STDOUT:   }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%X
 // CHECK:STDOUT: }
 // CHECK:STDOUT: