Reduce true/false conditionals down to just 'else' and warn if else is used in non-final branch

crsn/src/asm/instr/cond.rs

@@ -138,8 +138,7 @@ pub fn parse_cond(text: &str, pos: &SourcePosition) -> Result<Cond, CrsnError> {
         "neof" => Cond::NotEof,
         "ov" => Cond::Overflow,
         "nov" => Cond::NotOverflow,
-        "true" | "always" | "else" => Cond::True,
-        "false" | "never" => Cond::False,
+        "else" => Cond::True,
         _ => {
             return Err(CrsnError::Parse(format!("Unknown cond: {}", text).into(), pos.clone()));
         }
@@ -180,8 +179,8 @@ impl Display for Cond {
             Cond::Valid => "valid",
             Cond::Eof => "eof",
             Cond::NotEof => "neof",
-            Cond::True => "true",
-            Cond::False => "false",
+            Cond::True => "else",
+            Cond::False => "never",
         })
     }
 }

crsn/src/asm/instr/flatten.rs

@@ -49,6 +49,10 @@ impl Flatten for InstrWithBranches {
                     return Err(CrsnError::Asm(AsmError::ConditionalAlreadyUsed(cond), branch.pos()));
                 }
 
+                if cnt != branch_count - 1 && cond == Cond::True {
+                    warn!("\"Else\" conditional used in non-final branch at {}:{}", branch.pos().line, branch.pos().column);
+                }
+
                 let next_lbl = if cnt == branch_count - 1 {
                     end_lbl.clone()
                 } else {

examples/test_cond.csn

@@ -2,7 +2,7 @@
   (ld r8 0)
 
   (ld r0 1
-    (true? (add r8 1))
+    (else? (add r8 1))
   )
 
   (sub r0 1
@@ -10,15 +10,8 @@
     (else? (add r8 1))
   )
 
-  (nop
-    (always? (add r8 1))
-  )
-
-  (nop
-    (never? (fault))
-  )
 
-  (cmp r8 3
+  (cmp r8 2
     (ne? (fault))
   )
 )