SQL interpolation

[trevyn]

Instead of

let new_name = "Joey";
execute!("UPDATE person SET age = ?, name = ? WHERE name = ?", 18, new_name, "Joe")?;

we may wish to do something like

let new_name = "Joey";
execute!(r#"UPDATE person SET age = {18}, name = {new_name} WHERE name = {"Joe"}"#)?;

or, perhaps easier to implement properly,

let new_name = "Joey";
execute!("UPDATE person SET age = " 18 ", name = " new_name " WHERE name = " "Joe" "}")?;

See also:

• better string interpolation rust-lang/rfcs#1250
• Propose implicit named arguments for formatting macros rust-lang/rfcs#2795
• https://rust-lang.github.io/rfcs/2795-format-args-implicit-identifiers.html
• Tracking issue for format_args_capture rust-lang/rust#67984
• https://github.com/ct-austin/ifmt
• https://github.com/danielhenrymantilla/fstrings-rs

[trevyn]

xref: rust-lang/rust#90473

[trevyn]

Implementation idea for "implicit named arguments" and expressions in the style of rust-lang/rfcs#2795: Just replace with ? and use https://docs.rs/syn/latest/syn/fn.parse_str.html

Only allow relatively straightforward replacements and SQL, and provide a fallback to positional-argument-only mode: select_positional / execute_positional? Or if it fails to validate, fall back to attempting positional.

[trevyn]

d21f353 allows named SQL parameters that capture from local scope; this should be enough for many use-cases.