.config/nvim/after/plugin/rt.lua

-- local opts = {
--   tools = { -- rust-tools options
--     -- automatically call RustReloadWorkspace when writing to a Cargo.toml file.
--     reload_workspace_from_cargo_toml = true,

--     -- These apply to the default RustSetInlayHints command
--     inlay_hints = {
--       -- automatically set inlay hints (type hints)
--       -- default: true
--       auto = true,

--       -- Only show inlay hints for the current line
--       only_current_line = false,

--       -- whether to show parameter hints with the inlay hints or not
--       -- default: true
--       show_parameter_hints = true,

--       -- prefix for parameter hints
--       -- default: "<-"
--       parameter_hints_prefix = "<- ",

--       -- prefix for all the other hints (type, chaining)
--       -- default: "=>"
--       other_hints_prefix = "=> ",

--       -- whether to align to the length of the longest line in the file
--       max_len_align = false,

--       -- padding from the left if max_len_align is true
--       max_len_align_padding = 1,

--       -- whether to align to the extreme right or not
--       right_align = false,

--       -- padding from the right if right_align is true
--       right_align_padding = 7,

--       -- The color of the hints
--       highlight = "Comment",
--     },
--   },
-- }

-- require('rust-tools').setup(opts)