theia: Activating extension rust-analyzer failed: vscode.languages.registerDocumentSemanticTokensProvider is not a function.

Description

The rust-analyzer extension requires functions that are not yet implemented by Theia

Reproduction Steps

Download rust-analyzer.vsix from https://github.com/rust-analyzer/rust-analyzer/releases/tag/2020-04-13

Copy it to the plugins folder in theia’s git tree

Also download the rust-analyzer-linux binary and name it rust-analyzer and make sure it’s in Theia’s server process PATH variable

run: $ yarn start:browser

Open http://localhost:3000 in your browser

Open a rust project, e.g. cargo init in a folder

Or clone some Rust project such as: https://github.com/yewstack/yew

OS and Theia version:

a187f0141015f3e00e0844bec10dd9c97414b7ec Fedora on ppc64le (architecture not relevant to the bug, don’t worry)

Diagnostics:

An error message appears on the bottom right:

“Activating extension rust-analyzer failed: vscode.languages.registerDocumentSemanticTokensProvider is not a function.”