[repl] [bugfix] "var a string" returns *interface{}

This is odd. Yaegi returns last evaluated expression to the user, which is a pointer to an empty interface. But it supposed to be a string.

This commit fixes the issue (hopefully).

devtools/internal/interpreter/interpreter.go

@@ -233,10 +233,7 @@ func (i Instance) runGoCode(source string) (r EvalResult, e error) {
 	// if source is a statement or an expression. If source is a statement and previously source was an expression
 	// then Yaegi returns the same result again. That's why following code overrides last computed result to the value
 	// used as a discriminator for no result.
-	_, err := i.yaegi.Eval("interpreter.noResult{}")
-	if err != nil {
-		return GoCodeExecuted, fmt.Errorf("yaegi Eval failed: %w", err)
-	}
+	source = "interpreter.noResult{}; " + source
 
 	res, err := i.yaegi.Eval(source)
 	if err != nil {

devtools/internal/interpreter/interpreter_test.go

@@ -32,6 +32,11 @@ func TestEval(t *testing.T) {
 				code:           "pi.Spr(0,0,0)",
 				expectedResult: interpreter.GoCodeExecuted,
 			},
+			"var declaration": {
+				code:           "var a string",
+				expectedOutput: "string: \n",
+				expectedResult: interpreter.GoCodeExecuted,
+			},
 			"expression returning a struct": {
 				code:           "struct{}{}",
 				expectedOutput: "struct {}: {}\n",