Potential character range mis-calculation leading to erroneous text replacement

rust-analyzer version: rust-analyzer 1.65.0-nightly (2befdefd 2022-08-06)

rustc version: rustc 1.67.1 (d5a82bbd2 2023-02-07)

relevant settings: Editor is BBEdit version 14.6.4

Reproduction example: https://github.com/fspeirs/bbedit-rust-analyzer-bug/ @ 5fc0a1b

I noticed an issue in BBEdit when using rust-analyzer when I wanted to change L1 in bbedit_test::main.rs.

use bbedit_lib::add;

becomes:

use bbedit_lib::{bbedit_do_thing, add};

I can reproduce the bug by:

• Select the text "add" in the import line.
• Type { to wrap it in braces
• Left arrow to move to after the opening brace
• Type-select "bbedi" to import "bbedit_do_thing"
• Tab to accept the completion.

Expected result: that the braces would contain {bbedit_do_thing, add}

Result: add is overwritten with bbedit_do_thing.

Feedback from BareBones tech support:

When requesting the completion, BBEdit sends the following position parameter in the request:

    position =     {
        character = 22;
        line = 0;
    };

Character position 22 corresponds to where the insertion point is after typing "bbedi" just inside the open brace.

The response from the server includes an entry for bbedit_do_thing:

    {
        additionalTextEdits = (
        );
        deprecated = 0;
        detail = "fn()";
        filterText = "bbedit_do_thing";
        kind = 3;
        label = "bbedit_do_thing";
        preselect = 1;
        sortText = ffffffef;
        textEdit =             {
            newText = "bbedit_do_thing";
            range =                 {
                end =                     {
                    character = 25;
                    line = 0;
                };
                start =                     {
                    character = 17;
                    line = 0;
                };
            };
        };
   }

The textEdit value is an instruction to replace characters 17 through 25 on the first line with "bbedit_do_thing". This range includes the "add" that was already there.

When BBEdit follows the instruction specified by the server, the practical effect is to replace the add with bbedit_do_thing.

Start with the linked reproduction at fspeirs/bbedit-rust-analyzer-bug commit 5fc0a1b and the reported completion request and textEdit range. Trace how rust-analyzer calculates completion replacement ranges for the BBEdit sequence, then verify that accepting the completion preserves add inside the braces as expected.