diff --git a/rinja_parser/src/expr.rs b/rinja_parser/src/expr.rs
index c639260c..2f6bb4c2 100644
--- a/rinja_parser/src/expr.rs
+++ b/rinja_parser/src/expr.rs
@@ -202,16 +202,14 @@ impl<'a> Expr<'a> {
             Some("as") => {
                 let (i, target) = opt(identifier)(j)?;
                 let target = target.unwrap_or_default();
-                return match target {
-                    "bool" | "f16" | "f32" | "f64" | "f128" | "i8" | "i16" | "i32" | "i64"
-                    | "i128" | "isize" | "u8" | "u16" | "u32" | "u64" | "u128" | "usize" => {
-                        Ok((i, WithSpan::new(Self::As(Box::new(lhs), target), start)))
-                    }
-                    _ => Err(nom::Err::Failure(ErrorContext::new(
+                if crate::PRIMITIVE_TYPES.contains(&target) {
+                    return Ok((i, WithSpan::new(Self::As(Box::new(lhs), target), start)));
+                } else {
+                    return Err(nom::Err::Failure(ErrorContext::new(
                         "operator `as` expects the name of a primitive type on its right-hand side",
                         j,
-                    ))),
-                };
+                    )));
+                }
             }
             _ => return Ok((i, lhs)),
         };
diff --git a/rinja_parser/src/lib.rs b/rinja_parser/src/lib.rs
index fc809e24..5f6078f6 100644
--- a/rinja_parser/src/lib.rs
+++ b/rinja_parser/src/lib.rs
@@ -416,20 +416,15 @@ fn bool_lit(i: &str) -> ParseResult<'_> {
 }
 
 fn num_lit(i: &str) -> ParseResult<'_> {
-    const INTEGER_SUFFIX: &[&str] = &[
-        "i8", "i16", "i32", "i64", "i128", "isize", "u8", "u16", "u32", "u64", "u128", "usize",
-    ];
-    const FLOAT_SUFFIX: &[&str] = &["f16", "f32", "f64", "f128"];
-
     fn suffix<'a>(
         start: &'a str,
         kind: &'a str,
-        list: &'a [&[&str]],
+        list: &'a [&str],
         ignore: &'a [&str],
     ) -> impl Fn(&'a str) -> ParseResult<'a> + Copy + 'a {
         move |i| {
             let (i, suffix) = identifier(i)?;
-            if list.iter().flat_map(|&i| i).any(|&item| item == suffix) {
+            if list.contains(&suffix) {
                 Ok((i, suffix))
             } else if ignore.contains(&suffix) {
                 // no need for a message, this case only occures in an `opt(…)`
@@ -443,9 +438,9 @@ fn num_lit(i: &str) -> ParseResult<'_> {
         }
     }
 
-    let integer_suffix = suffix(i, "integer", &[INTEGER_SUFFIX], &[]);
-    let float_suffix = suffix(i, "float", &[FLOAT_SUFFIX], &["e"]);
-    let either_suffix = suffix(i, "number", &[INTEGER_SUFFIX, FLOAT_SUFFIX], &["e"]);
+    let integer_suffix = suffix(i, "integer", INTEGER_TYPES, &[]);
+    let float_suffix = suffix(i, "float", FLOAT_TYPES, &["e"]);
+    let either_suffix = suffix(i, "number", NUM_TYPES, &["e"]);
 
     recognize(tuple((
         opt(char('-')),
@@ -809,6 +804,47 @@ pub fn strip_common(base: &Path, path: &Path) -> String {
     }
 }
 
+/// Primitive integer types. Also used as number suffixes.
+const INTEGER_TYPES: &[&str] = &[
+    "i8", "i16", "i32", "i64", "i128", "isize", "u8", "u16", "u32", "u64", "u128", "usize",
+];
+
+/// Primitive floating point types. Also used as number suffixes.
+const FLOAT_TYPES: &[&str] = &["f16", "f32", "f64", "f128"];
+
+/// Primitive numeric types. Also used as number suffixes.
+const NUM_TYPES: &[&str] = &{
+    let mut list = [""; INTEGER_TYPES.len() + FLOAT_TYPES.len()];
+    let mut i = 0;
+    let mut o = 0;
+    while i < INTEGER_TYPES.len() {
+        list[o] = INTEGER_TYPES[i];
+        i += 1;
+        o += 1;
+    }
+    let mut i = 0;
+    while i < FLOAT_TYPES.len() {
+        list[o] = FLOAT_TYPES[i];
+        i += 1;
+        o += 1;
+    }
+    list
+};
+
+/// Complete list of named primitive types.
+const PRIMITIVE_TYPES: &[&str] = &{
+    let mut list = [""; NUM_TYPES.len() + 1];
+    let mut i = 0;
+    let mut o = 0;
+    while i < NUM_TYPES.len() {
+        list[o] = NUM_TYPES[i];
+        i += 1;
+        o += 1;
+    }
+    list[o] = "bool";
+    list
+};
+
 #[cfg(not(windows))]
 #[cfg(test)]
 mod test {