proc: return error when assigning between function variables (#2692)

Fixes #2691

pkg/proc/eval.go

@@ -383,6 +383,13 @@ func (scope *EvalScope) setValue(dstv, srcv *Variable, srcExpr string) error {
 		real, _ := constant.Float64Val(constant.Real(srcv.Value))
 		imag, _ := constant.Float64Val(constant.Imag(srcv.Value))
 		return dstv.writeComplex(real, imag, dstv.RealType.Size())
+	case reflect.Func:
+		if dstv.RealType.Size() == 0 {
+			if dstv.Name != "" {
+				return fmt.Errorf("can not assign to %s", dstv.Name)
+			}
+			return errors.New("can not assign to function expression")
+		}
 	}
 
 	// nilling nillable variables

pkg/proc/proc_test.go

@@ -5681,3 +5681,18 @@ func TestWatchpointStackBackwardsOutOfScope(t *testing.T) {
 		}
 	})
 }
+
+func TestSetOnFunctions(t *testing.T) {
+	// The set command between function variables should fail with an error
+	// Issue #2691
+	withTestProcess("goroutinestackprog", t, func(p *proc.Target, fixture protest.Fixture) {
+		setFunctionBreakpoint(p, t, "main.main")
+		assertNoError(p.Continue(), t, "Continue()")
+		scope, err := proc.GoroutineScope(p, p.CurrentThread())
+		assertNoError(err, t, "GoroutineScope")
+		err = scope.SetVariable("main.func1", "main.func2")
+		if err == nil {
+			t.Fatal("expected error when assigning between function variables")
+		}
+	})
+}