`replace_let_with_if_let` panics on unterminated string literal

when invoking Replace let with if let on a let binding whose initializer is an unterminated string literal r-a panics inside the assist handler. the syntax tree is parseable but incomplete and SyntaxFactory::expr_if calls ast.then_branch().unwrap() on the constructed node without guarding against the case where the branch is absent returning None for malformed input and causing an unconditional unwrap failure.

reproduce:

let s = "foo

place cursor on the l of let and apply Replace let with if let.

expected:
the assist should either transform the binding correctly or report that it cannot handle the incomplete expression, without crashing the server.

actual:
thread 'main' panicked at 'called Option::unwrap() on a None value', crates/syntax/src/ast/syntax_factory/constructors.rs:1141

the language server crashes and the editor loses all diagnostics and completions until it restarts.

env:

• rustc: 1.94.0
• rust-analyzer: 0.3.2854
• OS: Ubuntu
• Editor: VS Code

Reproduce the crash by applying Replace let with if let to the unterminated string example, then inspect crates/syntax/src/ast/syntax_factory/constructors.rs:1141 and the SyntaxFactory::expr_if path. Done means malformed input no longer panics and the assist either transforms the binding or reports that it cannot handle the incomplete expression.