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Simplify code, document logic, refactor and better error messages.

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This commit is contained in:
Stephen Chung 2020-03-06 01:05:02 +08:00
parent 883f08c026
commit 3d3b939ba6
4 changed files with 220 additions and 150 deletions
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232
src/engine.rs
View File

@ -105,21 +105,16 @@ impl Engine<'_> {
if let Some(f) = fn_def {
match *f {
FnIntExt::Ext(ref f) => {
let r = f(args, pos);
if r.is_err() {
return r;
}
let r = f(args, pos)?;
let callback = match spec.name.as_ref() {
KEYWORD_PRINT => self.on_print.as_mut(),
KEYWORD_DEBUG => self.on_debug.as_mut(),
_ => return r,
_ => return Ok(r),
};
Ok(callback(
&r.unwrap()
.downcast::<String>()
&r.downcast::<String>()
.map(|s| *s)
.unwrap_or("error: not a string".into()),
)
@ -172,6 +167,7 @@ impl Engine<'_> {
}
}
/// Chain-evaluate a dot setter
fn get_dot_val_helper(
&mut self,
scope: &mut Scope,
@ -181,6 +177,7 @@ impl Engine<'_> {
use std::iter::once;
match dot_rhs {
// xxx.fn_name(args)
Expr::FunctionCall(fn_name, args, def_value, pos) => {
let mut args: Array = args
.iter()
@ -194,17 +191,16 @@ impl Engine<'_> {
self.call_fn_raw(fn_name, args, def_value.as_ref(), *pos)
}
// xxx.id
Expr::Identifier(id, pos) => {
let get_fn_name = format!("get${}", id);
self.call_fn_raw(&get_fn_name, vec![this_ptr], None, *pos)
}
// xxx.lhs[idx_expr]
Expr::Index(lhs, idx_expr) => {
let idx = *self
.eval_expr(scope, idx_expr)?
.downcast::<i64>()
.map_err(|_| EvalAltResult::ErrorIndexExpr(idx_expr.position()))?;
let idx = self.eval_index_value(scope, idx_expr)?;
let (lhs_value, pos) = match lhs.as_ref() {
Expr::Identifier(id, pos) => {
@ -220,18 +216,18 @@ impl Engine<'_> {
Self::get_indexed_value(lhs_value, idx, pos).map(|(v, _)| v)
}
Expr::Dot(inner_lhs, inner_rhs) => match inner_lhs.as_ref() {
// xxx.lhs.rhs
Expr::Dot(lhs, rhs) => match lhs.as_ref() {
// xxx.id.rhs
Expr::Identifier(id, pos) => {
let get_fn_name = format!("get${}", id);
self.call_fn_raw(&get_fn_name, vec![this_ptr], None, *pos)
.and_then(|mut v| self.get_dot_val_helper(scope, v.as_mut(), inner_rhs))
.and_then(|mut v| self.get_dot_val_helper(scope, v.as_mut(), rhs))
}
// xxx.lhs[idx_expr].rhs
Expr::Index(lhs, idx_expr) => {
let idx = *self
.eval_expr(scope, idx_expr)?
.downcast::<i64>()
.map_err(|_| EvalAltResult::ErrorIndexExpr(idx_expr.position()))?;
let idx = self.eval_index_value(scope, idx_expr)?;
let (lhs_value, pos) = match lhs.as_ref() {
Expr::Identifier(id, pos) => {
@ -245,16 +241,19 @@ impl Engine<'_> {
};
Self::get_indexed_value(lhs_value, idx, pos).and_then(|(mut value, _)| {
self.get_dot_val_helper(scope, value.as_mut(), inner_rhs)
self.get_dot_val_helper(scope, value.as_mut(), rhs)
})
}
_ => Err(EvalAltResult::ErrorDotExpr(inner_lhs.position())),
// Syntax error
_ => Err(EvalAltResult::ErrorDotExpr(lhs.position())),
},
// Syntax error
_ => Err(EvalAltResult::ErrorDotExpr(dot_rhs.position())),
}
}
/// Search for a variable within the scope, returning its value and index inside the Scope
fn search_scope<T>(
scope: &Scope,
id: &str,
@ -267,13 +266,26 @@ impl Engine<'_> {
.and_then(move |(idx, _, val)| map(val).map(|v| (idx, v)))
}
/// Evaluate the value of an index (must evaluate to i64)
fn eval_index_value(
&mut self,
scope: &mut Scope,
idx_expr: &Expr,
) -> Result<i64, EvalAltResult> {
self.eval_expr(scope, idx_expr)?
.downcast::<i64>()
.map(|v| *v)
.map_err(|_| EvalAltResult::ErrorIndexExpr(idx_expr.position()))
}
/// Get the value at the indexed position of a base type
fn get_indexed_value(
val: Dynamic,
idx: i64,
pos: Position,
) -> Result<(Dynamic, VariableType), EvalAltResult> {
if val.is::<Array>() {
let arr = val.downcast::<Array>().unwrap();
let arr = val.downcast::<Array>().expect("Array expected");
if idx >= 0 {
arr.get(idx as usize)
@ -284,7 +296,7 @@ impl Engine<'_> {
Err(EvalAltResult::ErrorArrayBounds(arr.len(), idx, pos))
}
} else if val.is::<String>() {
let s = val.downcast::<String>().unwrap();
let s = val.downcast::<String>().expect("String expected");
if idx >= 0 {
s.chars()
@ -303,16 +315,14 @@ impl Engine<'_> {
}
}
/// Evaluate an index expression
fn eval_index_expr(
&mut self,
scope: &mut Scope,
lhs: &Expr,
idx_expr: &Expr,
) -> Result<(VariableType, Option<(String, usize)>, usize, Dynamic), EvalAltResult> {
let idx = *self
.eval_expr(scope, idx_expr)?
.downcast::<i64>()
.map_err(|_| EvalAltResult::ErrorIndexExpr(idx_expr.position()))?;
let idx = self.eval_index_value(scope, idx_expr)?;
match lhs {
Expr::Identifier(id, _) => Self::search_scope(
@ -330,9 +340,10 @@ impl Engine<'_> {
}
}
/// Replace a character at an index position in a mutable string
fn str_replace_char(s: &mut String, idx: usize, new_ch: char) {
// The new character
let ch = s.chars().nth(idx).unwrap();
let ch = s.chars().nth(idx).expect("string index out of bounds");
// See if changed - if so, update the String
if ch == new_ch {
@ -346,6 +357,35 @@ impl Engine<'_> {
chars.iter().for_each(|&ch| s.push(ch));
}
/// Update the value at an index position in a variable inside the scope
fn update_indexed_variable_in_scope(
source_type: VariableType,
scope: &mut Scope,
id: &str,
src_idx: usize,
idx: usize,
val: Dynamic,
) -> Option<Dynamic> {
match source_type {
VariableType::Array => {
let arr = scope.get_mut_by_type::<Array>(id, src_idx);
Some((arr[idx as usize] = val).into_dynamic())
}
VariableType::String => {
let s = scope.get_mut_by_type::<String>(id, src_idx);
// Value must be a character
let ch = *val
.downcast::<char>()
.expect("value to update an index position in a string must be a char");
Some(Self::str_replace_char(s, idx as usize, ch).into_dynamic())
}
_ => None,
}
}
/// Evaluate a dot chain getter
fn get_dot_val(
&mut self,
scope: &mut Scope,
@ -353,6 +393,7 @@ impl Engine<'_> {
dot_rhs: &Expr,
) -> Result<Dynamic, EvalAltResult> {
match dot_lhs {
// xxx.???
Expr::Identifier(id, pos) => {
let (sc_idx, mut target) = Self::search_scope(scope, id, Ok, *pos)?;
let value = self.get_dot_val_helper(scope, target.as_mut(), dot_rhs);
@ -364,6 +405,7 @@ impl Engine<'_> {
value
}
// lhs[idx_expr].???
Expr::Index(lhs, idx_expr) => {
let (source_type, src, idx, mut target) =
self.eval_index_expr(scope, lhs, idx_expr)?;
@ -371,39 +413,27 @@ impl Engine<'_> {
// In case the expression mutated `target`, we need to reassign it because
// of the above `clone`.
match source_type {
VariableType::Array => {
let src = src.unwrap();
scope
.get_mut(&src.0, src.1)
.downcast_mut::<Array>()
.unwrap()[idx] = target
}
VariableType::String => {
let src = src.unwrap();
Self::str_replace_char(
scope
.get_mut(&src.0, src.1)
.downcast_mut::<String>()
.unwrap(), // Root is a string
if let Some((id, src_idx)) = src {
Self::update_indexed_variable_in_scope(
source_type,
scope,
&id,
src_idx,
idx,
*target.downcast::<char>().unwrap(), // Target should be a char
target,
)
}
_ => panic!("source_type must be either Array or String"),
.expect("source_type must be either Array or String");
}
value
}
// Syntax error
_ => Err(EvalAltResult::ErrorDotExpr(dot_lhs.position())),
}
}
/// Chain-evaluate a dot setter
fn set_dot_val_helper(
&mut self,
this_ptr: &mut Variant,
@ -411,6 +441,7 @@ impl Engine<'_> {
mut source_val: Dynamic,
) -> Result<Dynamic, EvalAltResult> {
match dot_rhs {
// xxx.id
Expr::Identifier(id, pos) => {
let set_fn_name = format!("set${}", id);
@ -422,13 +453,14 @@ impl Engine<'_> {
)
}
Expr::Dot(inner_lhs, inner_rhs) => match inner_lhs.as_ref() {
// xxx.lhs.rhs
Expr::Dot(lhs, rhs) => match lhs.as_ref() {
Expr::Identifier(id, pos) => {
let get_fn_name = format!("get${}", id);
self.call_fn_raw(&get_fn_name, vec![this_ptr], None, *pos)
.and_then(|mut v| {
self.set_dot_val_helper(v.as_mut(), inner_rhs, source_val)
self.set_dot_val_helper(v.as_mut(), rhs, source_val)
.map(|_| v) // Discard Ok return value
})
.and_then(|mut v| {
@ -437,13 +469,15 @@ impl Engine<'_> {
self.call_fn_raw(&set_fn_name, vec![this_ptr, v.as_mut()], None, *pos)
})
}
_ => Err(EvalAltResult::ErrorDotExpr(inner_lhs.position())),
_ => Err(EvalAltResult::ErrorDotExpr(lhs.position())),
},
// Syntax error
_ => Err(EvalAltResult::ErrorDotExpr(dot_rhs.position())),
}
}
// Evaluate a dot chain setter
fn set_dot_val(
&mut self,
scope: &mut Scope,
@ -452,6 +486,7 @@ impl Engine<'_> {
source_val: Dynamic,
) -> Result<Dynamic, EvalAltResult> {
match dot_lhs {
// id.???
Expr::Identifier(id, pos) => {
let (sc_idx, mut target) = Self::search_scope(scope, id, Ok, *pos)?;
let value = self.set_dot_val_helper(target.as_mut(), dot_rhs, source_val);
@ -463,6 +498,7 @@ impl Engine<'_> {
value
}
// lhs[idx_expr].???
Expr::Index(lhs, idx_expr) => {
let (source_type, src, idx, mut target) =
self.eval_index_expr(scope, lhs, idx_expr)?;
@ -471,39 +507,27 @@ impl Engine<'_> {
// In case the expression mutated `target`, we need to reassign it because
// of the above `clone`.
match source_type {
VariableType::Array => {
let src = src.unwrap();
let val = scope
.get_mut(&src.0, src.1)
.downcast_mut::<Array>()
.unwrap();
val[idx] = target
}
VariableType::String => {
let src = src.unwrap();
Self::str_replace_char(
scope
.get_mut(&src.0, src.1)
.downcast_mut::<String>()
.unwrap(), // Root is a string
if let Some((id, src_idx)) = src {
Self::update_indexed_variable_in_scope(
source_type,
scope,
&id,
src_idx,
idx,
*target.downcast::<char>().unwrap(), // Target should be a char
target,
)
}
_ => panic!("source_type must be either Array or String"),
.expect("source_type must be either Array or String");
}
value
}
// Syntax error
_ => Err(EvalAltResult::ErrorDotExpr(dot_lhs.position())),
}
}
/// Evaluate an expression
fn eval_expr(&mut self, scope: &mut Scope, expr: &Expr) -> Result<Dynamic, EvalAltResult> {
match expr {
Expr::IntegerConstant(i, _) => Ok((*i).into_dynamic()),
@ -517,10 +541,12 @@ impl Engine<'_> {
.eval_index_expr(scope, lhs, idx_expr)
.map(|(_, _, _, x)| x),
// lhs = rhs
Expr::Assignment(lhs, rhs) => {
let rhs_val = self.eval_expr(scope, rhs)?;
match lhs.as_ref() {
// name = rhs
Expr::Identifier(name, pos) => {
if let Some((idx, _, _)) = scope.get(name) {
*scope.get_mut(name, idx) = rhs_val;
@ -530,50 +556,34 @@ impl Engine<'_> {
}
}
// idx_lhs[idx_expr] = rhs
Expr::Index(idx_lhs, idx_expr) => {
let (source_type, src, idx, _) =
self.eval_index_expr(scope, idx_lhs, idx_expr)?;
match source_type {
VariableType::Array => {
let src = src.unwrap();
scope
.get_mut(&src.0, src.1)
.downcast_mut::<Array>()
.map(|arr| (arr[idx as usize] = rhs_val).into_dynamic())
.ok_or_else(|| {
EvalAltResult::ErrorIndexExpr(idx_lhs.position())
})
}
VariableType::String => {
let src = src.unwrap();
scope
.get_mut(&src.0, src.1)
.downcast_mut::<String>()
.map(|s| {
Self::str_replace_char(
s,
idx as usize,
*rhs_val.downcast::<char>().unwrap(),
if let Some((id, src_idx)) = src {
Self::update_indexed_variable_in_scope(
source_type,
scope,
&id,
src_idx,
idx,
rhs_val,
)
.into_dynamic()
})
} else {
None
}
.ok_or_else(|| {
EvalAltResult::ErrorIndexExpr(idx_lhs.position())
EvalAltResult::ErrorAssignmentToUnknownLHS(idx_lhs.position())
})
}
_ => Err(EvalAltResult::ErrorAssignmentToUnknownLHS(
idx_lhs.position(),
)),
}
}
// dot_lhs.dot_rhs = rhs
Expr::Dot(dot_lhs, dot_rhs) => {
self.set_dot_val(scope, dot_lhs, dot_rhs, rhs_val)
}
// Syntax error
_ => Err(EvalAltResult::ErrorAssignmentToUnknownLHS(lhs.position())),
}
}
@ -615,7 +625,8 @@ impl Engine<'_> {
.map_err(|_| {
EvalAltResult::ErrorBooleanArgMismatch("AND".into(), lhs.position())
})?
&& *self
&& // Short-circuit using &&
*self
.eval_expr(scope, &*rhs)?
.downcast::<bool>()
.map_err(|_| {
@ -630,7 +641,8 @@ impl Engine<'_> {
.map_err(|_| {
EvalAltResult::ErrorBooleanArgMismatch("OR".into(), lhs.position())
})?
|| *self
|| // Short-circuit using ||
*self
.eval_expr(scope, &*rhs)?
.downcast::<bool>()
.map_err(|_| {
@ -644,6 +656,7 @@ impl Engine<'_> {
}
}
/// Evaluate a statement
pub(crate) fn eval_stmt(
&mut self,
scope: &mut Scope,
@ -679,8 +692,8 @@ impl Engine<'_> {
.and_then(|guard_val| {
if *guard_val {
self.eval_stmt(scope, body)
} else if else_body.is_some() {
self.eval_stmt(scope, else_body.as_ref().unwrap())
} else if let Some(stmt) = else_body {
self.eval_stmt(scope, stmt.as_ref())
} else {
Ok(().into_dynamic())
}
@ -775,6 +788,7 @@ impl Engine<'_> {
}
}
/// Map a type_name into a pretty-print name
pub(crate) fn map_type_name<'a>(&'a self, name: &'a str) -> &'a str {
self.type_names
.get(name)

17
src/error.rs
View File

@ -56,13 +56,13 @@ pub enum ParseErrorType {
/// An unknown operator is encountered. Wrapped value is the operator.
UnknownOperator(String),
/// An open `(` is missing the corresponding closing `)`.
MissingRightParen,
MissingRightParen(String),
/// Expecting `(` but not finding one.
MissingLeftBrace,
/// An open `{` is missing the corresponding closing `}`.
MissingRightBrace,
MissingRightBrace(String),
/// An open `[` is missing the corresponding closing `]`.
MissingRightBracket,
MissingRightBracket(String),
/// An expression in function call arguments `()` has syntax error.
MalformedCallExpr,
/// An expression in indexing brackets `[]` has syntax error.
@ -104,10 +104,10 @@ impl Error for ParseError {
ParseErrorType::BadInput(ref p) => p,
ParseErrorType::InputPastEndOfFile => "Script is incomplete",
ParseErrorType::UnknownOperator(_) => "Unknown operator",
ParseErrorType::MissingRightParen => "Expecting ')'",
ParseErrorType::MissingRightParen(_) => "Expecting ')'",
ParseErrorType::MissingLeftBrace => "Expecting '{'",
ParseErrorType::MissingRightBrace => "Expecting '}'",
ParseErrorType::MissingRightBracket => "Expecting ']'",
ParseErrorType::MissingRightBrace(_) => "Expecting '}'",
ParseErrorType::MissingRightBracket(_) => "Expecting ']'",
ParseErrorType::MalformedCallExpr => "Invalid expression in function call arguments",
ParseErrorType::MalformedIndexExpr => "Invalid index in indexing expression",
ParseErrorType::VarExpectsIdentifier => "Expecting name of a variable",
@ -130,6 +130,11 @@ impl fmt::Display for ParseError {
ParseErrorType::FnMissingParams(ref s) => {
write!(f, "Missing parameters for function '{}'", s)?
}
ParseErrorType::MissingRightParen(ref s)
| ParseErrorType::MissingRightBrace(ref s)
| ParseErrorType::MissingRightBracket(ref s) => {
write!(f, "{} for {}", self.description(), s)?
}
_ => write!(f, "{}", self.description())?,
}

72
src/parser.rs
View File

@ -1043,7 +1043,16 @@ fn parse_paren_expr<'a>(
match input.next() {
Some((Token::RightParen, _)) => Ok(expr),
_ => Err(ParseError::new(PERR::MissingRightParen, Position::eof())),
Some((_, pos)) => {
return Err(ParseError::new(
PERR::MissingRightParen("a matching ( in the expression".into()),
pos,
))
}
None => Err(ParseError::new(
PERR::MissingRightParen("a matching ( in the expression".into()),
Position::eof(),
)),
}
}
@ -1068,8 +1077,24 @@ fn parse_call_expr<'a>(
return Ok(Expr::FunctionCall(id, args, None, begin));
}
Some(&(Token::Comma, _)) => (),
Some(&(_, pos)) => return Err(ParseError::new(PERR::MalformedCallExpr, pos)),
None => return Err(ParseError::new(PERR::MalformedCallExpr, Position::eof())),
Some(&(_, pos)) => {
return Err(ParseError::new(
PERR::MissingRightParen(format!(
"closing the arguments list to function call of '{}'",
id
)),
pos,
))
}
None => {
return Err(ParseError::new(
PERR::MissingRightParen(format!(
"closing the arguments list to function call of '{}'",
id
)),
Position::eof(),
))
}
}
input.next();
@ -1080,17 +1105,24 @@ fn parse_index_expr<'a>(
lhs: Box<Expr>,
input: &mut Peekable<TokenIterator<'a>>,
) -> Result<Expr, ParseError> {
match parse_expr(input) {
Ok(idx_expr) => match input.peek() {
parse_expr(input).and_then(|idx_expr| match input.peek() {
Some(&(Token::RightBracket, _)) => {
input.next();
return Ok(Expr::Index(lhs, Box::new(idx_expr)));
}
Some(&(_, pos)) => return Err(ParseError::new(PERR::MalformedIndexExpr, pos)),
None => return Err(ParseError::new(PERR::MalformedIndexExpr, Position::eof())),
},
Err(err) => return Err(ParseError::new(PERR::MalformedIndexExpr, err.position())),
Some(&(_, pos)) => {
return Err(ParseError::new(
PERR::MissingRightBracket("index expression".into()),
pos,
))
}
None => {
return Err(ParseError::new(
PERR::MissingRightBracket("index expression".into()),
Position::eof(),
))
}
})
}
fn parse_ident_expr<'a>(
@ -1141,8 +1173,14 @@ fn parse_array_expr<'a>(
input.next();
Ok(Expr::Array(arr, begin))
}
Some(&(_, pos)) => Err(ParseError::new(PERR::MissingRightBracket, pos)),
None => Err(ParseError::new(PERR::MissingRightBracket, Position::eof())),
Some(&(_, pos)) => Err(ParseError::new(
PERR::MissingRightBracket("the end of array literal".into()),
pos,
)),
None => Err(ParseError::new(
PERR::MissingRightBracket("the end of array literal".into()),
Position::eof(),
)),
}
}
@ -1462,7 +1500,7 @@ fn parse_binary_op<'a>(
}
token => {
return Err(ParseError::new(
PERR::UnknownOperator(token.syntax().to_string()),
PERR::UnknownOperator(token.syntax().into()),
pos,
))
}
@ -1599,8 +1637,14 @@ fn parse_block<'a>(input: &mut Peekable<TokenIterator<'a>>) -> Result<Stmt, Pars
input.next();
Ok(Stmt::Block(statements))
}
Some(&(_, pos)) => Err(ParseError::new(PERR::MissingRightBrace, pos)),
None => Err(ParseError::new(PERR::MissingRightBrace, Position::eof())),
Some(&(_, pos)) => Err(ParseError::new(
PERR::MissingRightBrace("end of block".into()),
pos,
)),
None => Err(ParseError::new(
PERR::MissingRightBrace("end of block".into()),
Position::eof(),
)),
}
}

7
src/scope.rs
View File

@ -85,6 +85,13 @@ impl Scope {
&mut entry.1
}
/// Get a mutable reference to a variable in the Scope and downcast it to a specific type
pub(crate) fn get_mut_by_type<T: Any + Clone>(&mut self, key: &str, index: usize) -> &mut T {
self.get_mut(key, index)
.downcast_mut::<T>()
.expect("wrong type cast")
}
/// Get an iterator to variables in the Scope.
pub fn iter(&self) -> impl Iterator<Item = (&str, &Dynamic)> {
self.0