void comptimenumber type for easier erroring on non-value ast nodes

src/comptime.rs

@@ -1520,6 +1520,10 @@ pub enum Error {
     FloatingCmp,
     #[error("Not a comptime expression.")]
     NotComptime,
+    #[error("void conversion.")]
+    VoidConversion,
+    #[error("invalid conversion.")]
+    InvalidConversion,
 }
 
 pub type Result<T> = core::result::Result<T, Error>;
@@ -1967,6 +1971,7 @@ pub enum ComptimeNumber {
     Integral(ComptimeInt),
     Bool(bool),
     Floating(ComptimeFloat),
+    Void,
 }
 
 impl From<bool> for ComptimeNumber {
@@ -2017,6 +2022,7 @@ impl ComptimeNumber {
                 ComptimeFloat::Binary32(_) => 32,
                 ComptimeFloat::Binary64(_) => 64,
             },
+            ComptimeNumber::Void => 0,
         }
     }
     pub fn add(self, other: Self) -> Result<Self> {
@@ -2248,6 +2254,9 @@ impl ComptimeNumber {
                 ComptimeFloat::Binary32(f) => Ok((f as u128 & ty.u128_bitmask(), ty).into()),
                 ComptimeFloat::Binary64(f) => Ok((f as u128 & ty.u128_bitmask(), ty).into()),
             },
+            ComptimeNumber::Void => {
+                return Err(Error::VoidConversion);
+            }
         }
     }
     pub fn into_float(self, ty: FloatingType) -> Result<Self> {
@@ -2269,6 +2278,9 @@ impl ComptimeNumber {
                 ComptimeFloat::Binary32(f) => f as f64,
                 ComptimeFloat::Binary64(f) => f as f64,
             },
+            ComptimeNumber::Void => {
+                return Err(Error::VoidConversion);
+            }
         };
 
         match ty {
@@ -2305,6 +2317,7 @@ impl ComptimeNumber {
                     Type::Floating(FloatingType::Binary64),
                 ),
             },
+            ComptimeNumber::Void => (vec![], Type::Void),
         }
     }
 }