x/tools/gopls: "type name %q without type spec" bug in Hover(reported by telemetry)

[adonovan]

This stack dNjCQg was reported by telemetry:

golang.hover:+142 is:

spec, ok := spec.(*ast.TypeSpec)
		if !ok {
			// We cannot find a TypeSpec for this type or alias declaration
			// (that is not a type parameter or a built-in).
			// This should be impossible even for ill-formed trees;
			// we suspect that AST repair may be creating inconsistent
			// positions. Don't report a bug in that case. (#64241)
			errorf := fmt.Errorf
			if !declPGF.Fixed() {
				errorf = bug.Errorf
			}
			return protocol.Range{}, nil, errorf("type name %q without type spec", obj.Name())
		}

gopls/bug
golang.org/x/tools/gopls/internal/util/bug.report:+35
golang.org/x/tools/gopls/internal/util/bug.Errorf:+2
golang.org/x/tools/gopls/internal/golang.hover:+142
golang.org/x/tools/gopls/internal/golang.Hover:+4
golang.org/x/tools/gopls/internal/server.(*server).Hover:+19
golang.org/x/tools/gopls/internal/protocol.serverDispatch:+335
golang.org/x/tools/gopls/internal/lsprpc.(*streamServer).ServeStream.ServerHandler.func3:+5
golang.org/x/tools/gopls/internal/lsprpc.(*streamServer).ServeStream.handshaker.func4:+52
golang.org/x/tools/gopls/internal/protocol.Handlers.MustReplyHandler.func1:+2
golang.org/x/tools/gopls/internal/protocol.Handlers.AsyncHandler.func2.2:+3
runtime.goexit:+0

golang.org/x/tools/gopls@v0.15.1 go1.22.0 darwin/arm64 vscode (1)

Issue created by golang.org/x/tools/gopls/internal/telemetry/cmd/stacks.

[adonovan]

This is a refinement (dup) of #64241.