Fix clippy lint

#[clippy(warn::or_fun_call)]

Author: Sh3Rm4n

macros/src/symbol.rs

@@ -31,7 +31,7 @@ impl<'a> Symbol<'a> {
     pub fn new(tag: &'a str, data: &'a str) -> Self {
         Self {
             // `CARGO_PKG_NAME` is set to the invoking package's name.
-            package: env::var("CARGO_PKG_NAME").unwrap_or("<unknown>".to_string()),
+            package: env::var("CARGO_PKG_NAME").unwrap_or_else(|_| "<unknown>".to_string()),
             disambiguator: {
                 // We want a deterministic, but unique-per-macro-invocation identifier. For that we
                 // hash the call site `Span`'s debug representation, which contains a counter that

parser/src/lib.rs

@@ -169,7 +169,7 @@ fn parse_param(mut input: &str, mode: ParserMode) -> Result<Param, Cow<'static,
 
     // First, optional argument index.
     let mut index = None;
-    let index_end = input.find(|c: char| !c.is_digit(10)).unwrap_or(input.len());
+    let index_end = input.find(|c: char| !c.is_digit(10)).unwrap_or_else(|| input.len());
 
     if index_end != 0 {
         index = Some(
@@ -188,7 +188,7 @@ fn parse_param(mut input: &str, mode: ParserMode) -> Result<Param, Cow<'static,
         input = &input[TYPE_PREFIX.len()..];
 
         // type is delimited by `HINT_PREFIX` or end-of-string
-        let type_end = input.find(HINT_PREFIX).unwrap_or(input.len());
+        let type_end = input.find(HINT_PREFIX).unwrap_or_else(|| input.len());
         let type_fragment = &input[..type_end];
 
         static FORMAT_ARRAY_START: &str = "[?;";