Refactor Mode and partial parser/codegen for eval/exec

Author: youknowone

bytecode/src/lib.rs

@@ -4,6 +4,9 @@
 #![doc(html_logo_url = "https://raw.githubusercontent.com/RustPython/RustPython/main/logo.png")]
 #![doc(html_root_url = "https://docs.rs/rustpython-bytecode/")]
 
+mod mode;
+pub use mode::Mode;
+
 use bitflags::bitflags;
 use bstr::ByteSlice;
 use itertools::Itertools;

bytecode/src/mode.rs

@@ -0,0 +1,32 @@
+#[derive(Clone, Copy)]
+pub enum Mode {
+    Exec,
+    Eval,
+    Single,
+    BlockExpr,
+}
+
+impl std::str::FromStr for Mode {
+    type Err = ModeParseError;
+
+    // To support `builtins.compile()` `mode` argument
+    fn from_str(s: &str) -> Result<Self, ModeParseError> {
+        match s {
+            "exec" => Ok(Mode::Exec),
+            "eval" => Ok(Mode::Eval),
+            "single" => Ok(Mode::Single),
+            _ => Err(ModeParseError { _priv: () }),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct ModeParseError {
+    _priv: (),
+}
+
+impl std::fmt::Display for ModeParseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(f, r#"mode should be "exec", "eval", or "single""#)
+    }
+}