Set type of measurement expression correctly (#52)

* Set type of measurement expression correctly
That is measuring a qubit or hardware qubit results in a bit.
Measuring a qubit register results in a bit register of the same length.

* Log semantic error for incorrectly typed args to `measure`.

Closes #51

crates/oq3_semantics/src/asg.rs

@@ -55,6 +55,7 @@ impl Program {
         let _ = &self.stmts.push(stmt);
     }
 
+    // FIXME: This should probably log a semantic error rather than panic.
     // The check should be done when checking syntax.
     // This check may be overly restrictive, as one might want to manipulate
     // or construct a `Program` in a way other than sequentially translating
@@ -578,10 +579,13 @@ impl MeasureExpression {
         &self.operand
     }
 
-    // FIXME: type may not be correct here.
-    // This assumes a single qubit is measured.
     pub fn to_texpr(self) -> TExpr {
-        TExpr::new(Expr::MeasureExpression(self), Type::Bit(IsConst::False))
+        let out_type = match self.operand.get_type() {
+            Type::Qubit | Type::HardwareQubit => Type::Bit(IsConst::False),
+            Type::QubitArray(dims) => Type::BitArray(dims.clone(), IsConst::False),
+            _ => Type::Undefined,
+        };
+        TExpr::new(Expr::MeasureExpression(self), out_type)
     }
 }
 

crates/oq3_semantics/src/syntax_to_semantics.rs

@@ -247,12 +247,18 @@ fn from_gate_operand(gate_operand: synast::GateOperand, context: &mut Context) -
         synast::GateOperand::HardwareQubit(ref hwq) => {
             asg::GateOperand::HardwareQubit(ast_hardware_qubit(hwq)).to_texpr(Type::HardwareQubit)
         }
-        synast::GateOperand::Identifier(identifier) => {
-            let (astidentifier, typ) = ast_identifier(&identifier, context);
+        synast::GateOperand::Identifier(ref identifier) => {
+            let (astidentifier, typ) = ast_identifier(identifier, context);
+            if !matches!(typ, Type::Qubit | Type::HardwareQubit) {
+                context.insert_error(IncompatibleTypesError, &gate_operand);
+            }
             asg::GateOperand::Identifier(astidentifier).to_texpr(typ)
         }
-        synast::GateOperand::IndexedIdentifier(indexed_identifier) => {
-            let (indexed_identifier, typ) = ast_indexed_identifier(&indexed_identifier, context);
+        synast::GateOperand::IndexedIdentifier(ref indexed_identifier) => {
+            let (indexed_identifier, typ) = ast_indexed_identifier(indexed_identifier, context);
+            if !matches!(typ, Type::QubitArray(_)) {
+                context.insert_error(IncompatibleTypesError, &gate_operand);
+            }
             asg::GateOperand::IndexedIdentifier(indexed_identifier).to_texpr(typ)
         }
     }

crates/oq3_semantics/tests/from_string_tests.rs

@@ -152,7 +152,7 @@ fn test_gate_call() {
 mygate(x, y) q;
 "##;
     let (program, errors, _symbol_table) = parse_string(code);
-    assert_eq!(errors.len(), 4);
+    assert_eq!(errors.len(), 5);
     assert_eq!(program.len(), 1);
 }