Fix bug in const evaluator (#2296)

Fixes #2294

Author: orpuente-MS

compiler/qsc_qasm3/src/parser/error.rs

@@ -122,7 +122,7 @@ pub enum ErrorKind {
     #[error("missing switch statement case labels")]
     #[diagnostic(code("Qasm3.Parse.MissingSwitchCaseLabels"))]
     MissingSwitchCaseLabels(#[label] Span),
-    #[error("missing switch statement case labels")]
+    #[error("missing gate call operands")]
     #[diagnostic(code("Qasm3.Parse.MissingGateCallOperands"))]
     MissingGateCallOperands(#[label] Span),
     #[error("expected an item or closing brace, found {0}")]

compiler/qsc_qasm3/src/semantic/ast/const_eval.rs

@@ -161,12 +161,13 @@ impl BinaryOpExpr {
     fn const_eval(&self, ctx: &mut Lowerer) -> Option<LiteralKind> {
         use LiteralKind::{Angle, Bit, Bitstring, Bool, Float, Int};
 
-        assert_binary_op_ty_invariant(self.op, &self.lhs.ty, &self.rhs.ty);
         let lhs = self.lhs.const_eval(ctx);
         let rhs = self.rhs.const_eval(ctx);
         let (lhs, rhs) = (lhs?, rhs?);
         let lhs_ty = &self.lhs.ty;
 
+        assert_binary_op_ty_invariant(self.op, &self.lhs.ty, &self.rhs.ty);
+
         match &self.op {
             // Bit Shifts
             BinOp::Shl => {

compiler/qsc_qasm3/src/tests/statement/const_eval.rs

@@ -1982,3 +1982,151 @@ fn cast_to_bit() -> miette::Result<(), Vec<Report>> {
     .assert_eq(&qsharp);
     Ok(())
 }
+
+#[test]
+fn binary_op_err_type_fails() {
+    let source = r#"
+        int[a + b] x = 2;
+    "#;
+
+    let Err(errs) = compile_qasm_to_qsharp(source) else {
+        panic!("should have generated an error");
+    };
+    let errs: Vec<_> = errs.iter().map(|e| format!("{e:?}")).collect();
+    let errs_string = errs.join("\n");
+    expect![[r#"
+        Qsc.Qasm3.Lowerer.UndefinedSymbol
+
+          x undefined symbol: a
+           ,-[Test.qasm:2:13]
+         1 | 
+         2 |         int[a + b] x = 2;
+           :             ^
+         3 |     
+           `----
+
+        Qsc.Qasm3.Lowerer.UndefinedSymbol
+
+          x undefined symbol: b
+           ,-[Test.qasm:2:17]
+         1 | 
+         2 |         int[a + b] x = 2;
+           :                 ^
+         3 |     
+           `----
+
+        Qsc.Qasm3.Lowerer.CannotCast
+
+          x cannot cast expression of type Err to type UInt(None, true)
+           ,-[Test.qasm:2:13]
+         1 | 
+         2 |         int[a + b] x = 2;
+           :             ^^^^^
+         3 |     
+           `----
+
+        Qsc.Qasm3.Compile.ExprMustBeConst
+
+          x expression must be const
+           ,-[Test.qasm:2:13]
+         1 | 
+         2 |         int[a + b] x = 2;
+           :             ^^^^^
+         3 |     
+           `----
+
+        Qsc.Qasm3.Lowerer.ExprMustBeConst
+
+          x designator must be a const expression
+           ,-[Test.qasm:2:13]
+         1 | 
+         2 |         int[a + b] x = 2;
+           :             ^^^^^
+         3 |     
+           `----
+
+        Qsc.Qasm3.Lowerer.CannotCastLiteral
+
+          x cannot cast literal expression of type Int(None, true) to type Err
+           ,-[Test.qasm:2:9]
+         1 | 
+         2 |         int[a + b] x = 2;
+           :         ^^^^^^^^^^^^^^^^^
+         3 |     
+           `----
+    "#]]
+    .assert_eq(&errs_string);
+}
+
+#[test]
+fn fuzzer_issue_2294() {
+    let source = r#"
+        ctrl(5/_)@l
+    "#;
+
+    let Err(errs) = compile_qasm_to_qsharp(source) else {
+        panic!("should have generated an error");
+    };
+    let errs: Vec<_> = errs.iter().map(|e| format!("{e:?}")).collect();
+    let errs_string = errs.join("\n");
+    expect![[r#"
+        Qasm3.Parse.Token
+
+          x expected `;`, found EOF
+           ,-[Test.qasm:3:5]
+         2 |         ctrl(5/_)@l
+         3 |     
+           `----
+
+        Qasm3.Parse.MissingGateCallOperands
+
+          x missing gate call operands
+           ,-[Test.qasm:2:9]
+         1 | 
+         2 |         ctrl(5/_)@l
+           :         ^^^^^^^^^^^
+         3 |     
+           `----
+
+        Qsc.Qasm3.Lowerer.UndefinedSymbol
+
+          x undefined symbol: _
+           ,-[Test.qasm:2:16]
+         1 | 
+         2 |         ctrl(5/_)@l
+           :                ^
+         3 |     
+           `----
+
+        Qsc.Qasm3.Lowerer.CannotCast
+
+          x cannot cast expression of type Err to type Float(None, true)
+           ,-[Test.qasm:2:16]
+         1 | 
+         2 |         ctrl(5/_)@l
+           :                ^
+         3 |     
+           `----
+
+        Qsc.Qasm3.Compile.ExprMustBeConst
+
+          x expression must be const
+           ,-[Test.qasm:2:16]
+         1 | 
+         2 |         ctrl(5/_)@l
+           :                ^
+         3 |     
+           `----
+
+        Qsc.Qasm3.Lowerer.ExprMustBeConst
+
+          x ctrl modifier argument must be a const expression
+           ,-[Test.qasm:2:14]
+         1 | 
+         2 |         ctrl(5/_)@l
+           :              ^^^
+         3 |     
+           `----
+    "#]]
+    .assert_eq(&errs_string);
+}