Fixed angle adjustment size bug (#2845)

There is a subtle bug in `AdjustAngleSize`.

When creating the new `Angle` struct in both the truncation and padding
branches, the codeuses the original size instead of `new_size`. This
means the `Value` is scaled to the new precision, but the `Size`
metadata remains incorrect.

This then cascades and impacts other functions that make use of `Size`,
e.g. `AngleAsResultArrayBE`.

I couldn't find any tests for that logic so I added a test with a new
mod. The test is also a repro and fails without the change.

Author: filipw

library/src/tests.rs

@@ -11,6 +11,7 @@ mod intrinsic;
 mod logical;
 mod math;
 mod measurement;
+mod openqasm;
 mod state_preparation;
 mod table_lookup;
 

library/src/tests/openqasm.rs

@@ -0,0 +1,4 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+mod angle;

library/src/tests/openqasm/angle.rs

@@ -0,0 +1,19 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+use crate::tests::test_expression;
+use indoc::indoc;
+use qsc::interpret::Value;
+
+#[test]
+fn check_adjust_angle_size_no_truncation_increases_size() {
+    test_expression(
+        indoc! {r#"{
+            import Std.OpenQASM.Angle.*;
+            let angle = IntAsAngle(100, 16);
+            let adjusted_angle = AdjustAngleSizeNoTruncation(angle, 32);
+            adjusted_angle.Size
+        }"#},
+        &Value::Int(32),
+    );
+}

library/std/src/Std/OpenQASM/Angle.qs

@@ -126,14 +126,14 @@ function AdjustAngleSize(angle : Angle, new_size : Int, truncate : Bool) : Angle
                 upper_bits
             }
         };
-        new Angle { Value = value, Size = size }
+        new Angle { Value = value, Size = new_size }
     } elif new_size == size {
         // Same size, no change
         angle
     } else {
         // Padding with zeros
         let value = value <<< (new_size - size);
-        new Angle { Value = value, Size = size }
+        new Angle { Value = value, Size = new_size }
     }
 }