Merge pull request #655 from OpenVADL/bugifx/fix-crash-constant-mismatch-shift

typechecker: Fix crash shift constant mismatch

Author: AndreasKrall

vadl/main/vadl/ast/TypeChecker.java

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText : © 2025 TU Wien <[email protected]>
+// SPDX-FileCopyrightText : © 2025-2026 TU Wien <[email protected]>
 // SPDX-License-Identifier: GPL-3.0-or-later
 //
 // This program is free software: you can redistribute it and/or modify
@@ -2593,9 +2593,23 @@ public Void visit(BinaryExpr expr) {
               .build());
         }
 
-        var result = constantEvaluator.eval(expr);
-        expr.type = result.type();
-        return null;
+        if (constantEvaluator.isConstant(expr.right)) {
+          var result = constantEvaluator.eval(expr);
+          expr.type = result.type();
+          return null;
+        }
+
+        // The left side is constant but the right isn't
+        // lets throw an error because it doesn't make sense to cast the left side to the right
+        // side if the types are independent of each other.
+        throw addErrorAndStopChecking(error("Type Mismatch", expr)
+            .description(
+                "%s",
+                "Cannot infer a type for the result of this operation, because the left side is "
+                    + "constant but the right side is not: `%s`.".formatted(rightTyp)
+            )
+            .help("You can cast the left argument to an explicit type.")
+            .build());
       }
 
       expr.type = leftTyp;

vadl/test/resources/diagnostics/typechecker/invalidShiftLeftConstRightExplicit.vadl

@@ -0,0 +1,26 @@
+// There has been a bug where the compiler crashed with this input
+// https://github.com/OpenVADL/openvadl/issues/654#issuecomment-3716074918
+
+instruction set architecture ISA = {
+   register A : Bits<32>
+
+   format T : Bits<1> = { a [0..0] }
+   instruction I: T = A := 6 >> a
+   assembly I = ("a", "b", 'c', 'd')
+   encoding I = {a = 1}
+}
+
+
+//  Reported Diagnostics:
+//
+//  error: Type Mismatch
+//       ╭──[test/resources/diagnostics/typechecker/invalidShiftLeftConstRightExplicit.vadl:8:28]
+//       │
+//     8 │    instruction I: T = A := 6 >> a
+//       │                            ^^^^^^
+//       │
+//       Cannot infer a type for the result of this operation, because the left side is constant but the right side is not: `UInt<1>`.
+//       help: You can cast the left argument to an explicit type.
+//
+//
+// Part of the class vadl.ast.DiagnosticsTest