Implement shorthand for array definition

examples/array_short.reid

@@ -0,0 +1,7 @@
+// Arithmetic, function calls and imports!
+
+fn main() -> u16 {
+  let mut a = [5; 20];
+
+  return a[15];
+}

reid/src/ast/mod.rs

@@ -57,6 +57,7 @@ pub enum ExpressionKind {
     Deref(String),
     Literal(Literal),
     Array(Vec<Expression>),
+    ArrayShort(Box<Expression>, u64),
     /// Array-indexed, e.g. <expr>[<expr>]
     Indexed(Box<Expression>, Box<Expression>),
     /// Struct-accessed, e.g. <expr>.<expr>

reid/src/ast/parse.rs

@@ -250,17 +250,38 @@ impl Parse for PrimaryExpression {
                 }
                 Token::BracketOpen => {
                     stream.next(); // Consume
-                    let mut expressions = Vec::new();
                     if let Ok(exp) = stream.parse() {
+                        if let Some(Token::Semi) = stream.peek() {
+                            stream.next(); // Consume colon
+                            let Some(Token::DecimalValue(val)) = stream.next() else {
+                                return Err(stream
+                                    .expecting_err("decimal value describing array length")?);
+                            };
+                            stream.expect(Token::BracketClose)?;
+                            Expression(
+                                Kind::ArrayShort(
+                                    Box::new(exp),
+                                    u64::from_str_radix(&val, 10).expect(
+                                        "Unable to parse array length to 64-bit decimal value",
+                                    ),
+                                ),
+                                stream.get_range().unwrap(),
+                            )
+                        } else {
+                            let mut expressions = Vec::new();
                             expressions.push(exp);
                             while let Some(Token::Comma) = stream.peek() {
                                 stream.next(); // Consume comma
                                 expressions.push(stream.parse()?);
                             }
-                    }
                             stream.expect(Token::BracketClose)?;
                             Expression(Kind::Array(expressions), stream.get_range().unwrap())
                         }
+                    } else {
+                        stream.expect(Token::BraceClose)?;
+                        Expression(Kind::Array(Vec::new()), stream.get_range().unwrap())
+                    }
+                }
                 _ => Err(stream.expecting_err("expression")?)?,
             }
         } else {

reid/src/ast/process.rs

@@ -378,6 +378,12 @@ impl ast::Expression {
                 Box::new(expression.process(module_id)),
                 ty.0.clone().into_mir(module_id),
             ),
+            ast::ExpressionKind::ArrayShort(expression, len) => mir::ExprKind::Array(
+                vec![*expression.clone(); *len as usize]
+                    .iter()
+                    .map(|e| e.process(module_id))
+                    .collect(),
+            ),
         };
 
         mir::Expression(kind, self.1.as_meta(module_id))