Add DeclarationLiteral parsing

Added method for parsing simple literals for use in top-level class
declarations.

Along with this change we've also moved out methods specific for parsing
low-level literals into the same file as new method, since that
structure made more sense.

rottlib/src/ast.rs

@@ -246,6 +246,17 @@ impl<'src, 'arena> Expression<'src, 'arena> {
     }
 }
 
+pub enum DeclarationLiteral<'src, 'arena> {
+    None,
+    Bool(bool),
+    Integer(i128),
+    Float(f64),
+    String(ArenaString<'arena>),
+    Identifier(&'src str),
+}
+
+pub type DeclarationLiteralRef<'src, 'arena> = (DeclarationLiteral<'src, 'arena>, TokenLocation);
+
 /// Returns `true` for expressions that require `;` when used as a statement
 /// (i.e., everything except blocky control-flow forms).
 pub trait NeedsSemi {

rottlib/src/parser/errors.rs

@@ -70,6 +70,11 @@ pub enum ParseErrorKind {
     DeclMissingIdentifier,
     /// Invalid variable name identifier in non-`local` variable definition.
     DeclBadVariableIdentifier,
+    /// Found an unexpected token while parsing a declaration literal.
+    ///
+    /// Expected one of: integer, float, string, `true`, `false`, `none`
+    /// or an identifier.
+    DeclarationLiteralUnexpectedToken,
 }
 
 /// Enumerates all specific kinds of parsing errors that the parser can emit.

rottlib/src/parser/grammar/literals.rs

@@ -0,0 +1,119 @@
+use crate::ast::DeclarationLiteral;
+use crate::lexer::Token;
+use crate::parser::{ParseErrorKind, ParseResult, ResultRecoveryExt};
+
+impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
+    /// Parses a simple literal value that can be used inside FerUS's top-level
+    /// class members' definitions.
+    ///
+    /// On success consumes exactly one token. If the next token is not
+    /// a supported literal, returns [`None`] and leaves the stream untouched.
+    pub(crate) fn parse_declaration_literal(
+        &mut self,
+    ) -> ParseResult<crate::ast::DeclarationLiteralRef> {
+        let Some((token, token_text, token_location)) = self.peek_token_lexeme_and_location()
+        else {
+            return Err(self.make_error_here(ParseErrorKind::UnexpectedEndOfFile));
+        };
+        let declaration_literal = match token {
+            Token::IntegerLiteral => {
+                let value = self
+                    .decode_integer_literal(token_text)
+                    .unwrap_or_fallback(self);
+                self.advance();
+                DeclarationLiteral::Integer(value)
+            }
+            Token::FloatLiteral => {
+                let value = self
+                    .decode_float_literal(token_text)
+                    .unwrap_or_fallback(self);
+                self.advance();
+                DeclarationLiteral::Float(value)
+            }
+            Token::StringLiteral => {
+                let value = crate::parser::Parser::unescape_string_literal(self.arena, token_text);
+                self.advance();
+                DeclarationLiteral::String(value)
+            }
+            Token::True => {
+                self.advance();
+                DeclarationLiteral::Bool(true)
+            }
+            Token::False => {
+                self.advance();
+                DeclarationLiteral::Bool(false)
+            }
+            Token::None => {
+                self.advance();
+                DeclarationLiteral::None
+            }
+            Token::Identifier => {
+                self.advance();
+                DeclarationLiteral::Identifier(token_text)
+            }
+            _ => {
+                return Err(self.make_error_here(ParseErrorKind::DeclarationLiteralUnexpectedToken));
+            }
+        };
+        Ok((declaration_literal, token_location))
+    }
+
+    /// Parses an integer literal as [`i128`].
+    ///
+    /// Expects a normalized decimal string with optional leading sign.
+    /// Does not accept base prefixes or digit separators.
+    ///
+    /// [`i128`] type was chosen to cover FerUS's integer range so constant
+    /// folding remains precise.
+    pub(crate) fn decode_integer_literal(&mut self, text: &str) -> ParseResult<i128> {
+        text.parse::<i128>()
+            .map_err(|_| self.make_error_here(ParseErrorKind::InvalidNumericLiteral))
+    }
+
+    /// Parses a float literal as [`f64`].
+    ///
+    /// Expects a normalized decimal float (optional sign, decimal point,
+    /// optional exponent). Special values like `inf`/`NaN` are rejected.
+    pub(crate) fn decode_float_literal(&mut self, text: &str) -> ParseResult<f64> {
+        if let Ok(parsed_value) = text.parse::<f64>() {
+            Ok(parsed_value)
+        } else {
+            Err(self.make_error_here(ParseErrorKind::InvalidNumericLiteral))
+        }
+    }
+
+    /// Unescapes a tokenized string literal into an arena string.
+    ///
+    /// Supported escapes: `\n`, `\t`, `\"`, `\\`.
+    /// Unknown escape sequences are preserved as-is (UnrealScript behavior).
+    ///
+    /// Note: this function assumes `raw` is the token text without surrounding
+    /// quotes.
+    pub(crate) fn unescape_string_literal(
+        arena: &'arena crate::arena::Arena,
+        raw: &str,
+    ) -> crate::arena::ArenaString<'arena> {
+        let mut buffer = String::with_capacity(raw.len());
+        let mut characters = raw.chars();
+        while let Some(next_character) = characters.next() {
+            if next_character == '\\' {
+                // The lexer never produces a trailing backslash in a string
+                // token, so there's always a following character to inspect.
+                if let Some(escaped_character) = characters.next() {
+                    match escaped_character {
+                        'n' => buffer.push('\n'),
+                        't' => buffer.push('\t'),
+                        '"' => buffer.push('"'),
+                        '\\' => buffer.push('\\'),
+                        // Simply leaving the escaped character as-is matches
+                        // UnrealScript behavior.
+                        other => buffer.push(other),
+                    }
+                }
+            } else {
+                buffer.push(next_character);
+            }
+        }
+        arena.string(&buffer)
+    }
+}

rottlib/src/parser/grammar/mod.rs

@@ -1,6 +1,7 @@
 mod block;
 mod control;
 mod flow;
+mod literals;
 mod pratt;
 mod precedence;
 mod statements;

rottlib/src/parser/grammar/pratt.rs

@@ -23,9 +23,7 @@
 
 use crate::ast::{Expression, ExpressionRef, NeedsSemi};
 use crate::lexer::{Token, TokenLocation};
-use crate::parser::{
-    ParseErrorKind, ParseExpressionResult, ParseResult, ResultRecoveryExt, SyncLevel,
-};
+use crate::parser::{ParseErrorKind, ParseExpressionResult, ResultRecoveryExt, SyncLevel};
 
 pub(crate) use super::precedence::PrecedenceRank;
 
@@ -96,21 +94,21 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
         };
         match token {
             Token::IntegerLiteral => {
-                let value = self.parse_integer_literal(token_text)?;
+                let value = self.decode_integer_literal(token_text)?;
                 self.advance();
                 Ok(self
                     .arena
                     .alloc_at(Expression::Integer(value), token_location))
             }
             Token::FloatLiteral => {
-                let value = self.parse_float_literal(token_text)?;
+                let value = self.decode_float_literal(token_text)?;
                 self.advance();
                 Ok(self
                     .arena
                     .alloc_at(Expression::Float(value), token_location))
             }
             Token::StringLiteral => {
-                let value = unescape_string_literal(self.arena, token_text);
+                let value = crate::parser::Parser::unescape_string_literal(self.arena, token_text);
                 self.advance();
                 Ok(self
                     .arena
@@ -260,33 +258,6 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
         left_hand_side
     }
 
-    /// Parses an integer literal as [`i128`].
-    ///
-    /// Chosen to cover FerUS's integer range so constant folding
-    /// remains precise.
-    ///
-    /// Errors with [`ParseErrorKind::InvalidNumericLiteral`] if `text` is
-    /// not a valid integer.
-    fn parse_integer_literal(&mut self, text: &str) -> ParseResult<i128> {
-        text.parse::<i128>()
-            .map_err(|_| self.make_error_here(ParseErrorKind::InvalidNumericLiteral))
-    }
-
-    /// Parses a float literal as [`f64`].
-    ///
-    /// Chosen to cover FerUS's float range so constant folding remains
-    /// precise.
-    ///
-    /// Errors with [`ParseErrorKind::InvalidNumericLiteral`] if `text` is
-    /// not a valid float.
-    fn parse_float_literal(&mut self, text: &str) -> ParseResult<f64> {
-        if let Ok(parsed_value) = text.parse::<f64>() {
-            Ok(parsed_value)
-        } else {
-            Err(self.make_error_here(ParseErrorKind::InvalidNumericLiteral))
-        }
-    }
-
     /// Returns the next postfix operator and its location if present.
     ///
     /// Helper to avoid peeking and mapping twice; used to drive the postfix
@@ -369,38 +340,3 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
         None
     }
 }
-
-/// Unescapes a tokenized string literal into an arena string.
-///
-/// Supported escapes: `\n`, `\t`, `\"`, `\\`.
-/// Unknown escape sequences are preserved as-is (UnrealScript behavior).
-///
-/// Note: this function assumes `raw` is the token text without surrounding
-/// quotes.
-fn unescape_string_literal<'arena>(
-    arena: &'arena crate::arena::Arena,
-    raw: &str,
-) -> crate::arena::ArenaString<'arena> {
-    let mut buffer = String::with_capacity(raw.len());
-    let mut characters = raw.chars();
-    while let Some(next_character) = characters.next() {
-        if next_character == '\\' {
-            // The lexer never produces a trailing backslash in a string token,
-            // so there's always a following character to inspect.
-            if let Some(escaped_character) = characters.next() {
-                match escaped_character {
-                    'n' => buffer.push('\n'),
-                    't' => buffer.push('\t'),
-                    '"' => buffer.push('"'),
-                    '\\' => buffer.push('\\'),
-                    // Simply leaving escaped character as-is is an expected
-                    // behavior by UnrealScript
-                    other => buffer.push(other),
-                }
-            }
-        } else {
-            buffer.push(next_character);
-        }
-    }
-    arena.string(&buffer)
-}

rottlib/src/parser/recovery.rs

@@ -4,6 +4,9 @@
 //! token is found. The sync target is chosen from [`SyncLevel`] based on
 //! the error kind. Methods on [`ParseResult`] let callers widen the error span,
 //! synchronize, report, and produce fallback values.
+//!
+//! General idea is that any method that returns something other than an error
+//! can be assumed to have reported it.
 
 use crate::lexer::{Token, TokenLocation};
 use crate::parser::{ParseError, ParseResult, Parser};
@@ -217,6 +220,18 @@ impl<'src, 'arena> ResultRecoveryExt<'src, 'arena, ()> for ParseError {
     }
 }
 
+impl<'src, 'arena> RecoveryFallback<'src, 'arena> for i128 {
+    fn fallback_value(_: &Parser<'src, 'arena>, _: &ParseError) -> Self {
+        i128::default()
+    }
+}
+
+impl<'src, 'arena> RecoveryFallback<'src, 'arena> for f64 {
+    fn fallback_value(_: &Parser<'src, 'arena>, _: &ParseError) -> Self {
+        f64::default()
+    }
+}
+
 impl<'src, 'arena> RecoveryFallback<'src, 'arena> for TokenLocation {
     fn fallback_value(_: &Parser<'src, 'arena>, error: &ParseError) -> Self {
         error.source_span.to