Warn if str.parse if no explicit type specified

What it does

Warn for &str.parse() if the inferred type is i32 without explicit specify.

Lint Name

STR_PARSE_INFER_TO_I32

Category

suspicious

Advantage

Hint developer that the parse actually only process i32, if the value is larger, the code fails.

Drawbacks

None

Example

x.parse().unwrap_or(0) 

Could be written as:

x.parse::<i32>().unwrap_or(0)

if "111111111111111111".parse().unwrap_or(0) > 0 {
    println!("good");
} else {
    println!("bad");
}

if "111111111111111111".parse::<_>().unwrap_or(0) > 0 {
    println!("good");
} else {
    println!("bad");
}

if "111111111111111111".parse::<i64>().unwrap_or(0) > 0 {
    println!("good");
} else {
    println!("bad");
}

outputs

bad
bad
good

Start by locating the existing str.parse handling and lint registration in rust-clippy, then inspect how similar suspicious lints express diagnostics and tests. Use the provided i32, inferred, and explicit i64 examples to define the expected warnings and non-warnings; done means the STR_PARSE_INFER_TO_I32 lint is implemented and covered by tests.