reorganize compiler crates

parser/src/error.rs

@@ -0,0 +1,235 @@
+//! Define internal parse error types
+//! The goal is to provide a matching and a safe error API, maksing errors from LALR
+use lalrpop_util::ParseError as LalrpopError;
+
+use crate::ast::Location;
+use crate::token::Tok;
+
+use std::error::Error;
+use std::fmt;
+
+/// Represents an error during lexical scanning.
+#[derive(Debug, PartialEq)]
+pub struct LexicalError {
+    pub error: LexicalErrorType,
+    pub location: Location,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum LexicalErrorType {
+    StringError,
+    UnicodeError,
+    NestingError,
+    IndentationError,
+    TabError,
+    TabsAfterSpaces,
+    DefaultArgumentError,
+    PositionalArgumentError,
+    DuplicateKeywordArgumentError,
+    UnrecognizedToken { tok: char },
+    FStringError(FStringErrorType),
+    LineContinuationError,
+    Eof,
+    OtherError(String),
+}
+
+impl fmt::Display for LexicalErrorType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            LexicalErrorType::StringError => write!(f, "Got unexpected string"),
+            LexicalErrorType::FStringError(error) => write!(f, "Got error in f-string: {}", error),
+            LexicalErrorType::UnicodeError => write!(f, "Got unexpected unicode"),
+            LexicalErrorType::NestingError => write!(f, "Got unexpected nesting"),
+            LexicalErrorType::IndentationError => {
+                write!(f, "unindent does not match any outer indentation level")
+            }
+            LexicalErrorType::TabError => {
+                write!(f, "inconsistent use of tabs and spaces in indentation")
+            }
+            LexicalErrorType::TabsAfterSpaces => {
+                write!(f, "Tabs not allowed as part of indentation after spaces")
+            }
+            LexicalErrorType::DefaultArgumentError => {
+                write!(f, "non-default argument follows default argument")
+            }
+            LexicalErrorType::DuplicateKeywordArgumentError => {
+                write!(f, "keyword argument repeated")
+            }
+            LexicalErrorType::PositionalArgumentError => {
+                write!(f, "positional argument follows keyword argument")
+            }
+            LexicalErrorType::UnrecognizedToken { tok } => {
+                write!(f, "Got unexpected token {}", tok)
+            }
+            LexicalErrorType::LineContinuationError => {
+                write!(f, "unexpected character after line continuation character")
+            }
+            LexicalErrorType::Eof => write!(f, "unexpected EOF while parsing"),
+            LexicalErrorType::OtherError(msg) => write!(f, "{}", msg),
+        }
+    }
+}
+
+// TODO: consolidate these with ParseError
+#[derive(Debug, PartialEq)]
+pub struct FStringError {
+    pub error: FStringErrorType,
+    pub location: Location,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum FStringErrorType {
+    UnclosedLbrace,
+    UnopenedRbrace,
+    ExpectedRbrace,
+    InvalidExpression(Box<ParseErrorType>),
+    InvalidConversionFlag,
+    EmptyExpression,
+    MismatchedDelimiter,
+    ExpressionNestedTooDeeply,
+}
+
+impl fmt::Display for FStringErrorType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            FStringErrorType::UnclosedLbrace => write!(f, "Unclosed '{{'"),
+            FStringErrorType::UnopenedRbrace => write!(f, "Unopened '}}'"),
+            FStringErrorType::ExpectedRbrace => write!(f, "Expected '}}' after conversion flag."),
+            FStringErrorType::InvalidExpression(error) => {
+                write!(f, "Invalid expression: {}", error)
+            }
+            FStringErrorType::InvalidConversionFlag => write!(f, "Invalid conversion flag"),
+            FStringErrorType::EmptyExpression => write!(f, "Empty expression"),
+            FStringErrorType::MismatchedDelimiter => write!(f, "Mismatched delimiter"),
+            FStringErrorType::ExpressionNestedTooDeeply => {
+                write!(f, "expressions nested too deeply")
+            }
+        }
+    }
+}
+
+impl From<FStringError> for LalrpopError<Location, Tok, LexicalError> {
+    fn from(err: FStringError) -> Self {
+        lalrpop_util::ParseError::User {
+            error: LexicalError {
+                error: LexicalErrorType::FStringError(err.error),
+                location: err.location,
+            },
+        }
+    }
+}
+
+/// Represents an error during parsing
+#[derive(Debug, PartialEq)]
+pub struct ParseError {
+    pub error: ParseErrorType,
+    pub location: Location,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum ParseErrorType {
+    /// Parser encountered an unexpected end of input
+    Eof,
+    /// Parser encountered an extra token
+    ExtraToken(Tok),
+    /// Parser encountered an invalid token
+    InvalidToken,
+    /// Parser encountered an unexpected token
+    UnrecognizedToken(Tok, Option<String>),
+    /// Maps to `User` type from `lalrpop-util`
+    Lexical(LexicalErrorType),
+}
+
+/// Convert `lalrpop_util::ParseError` to our internal type
+impl From<LalrpopError<Location, Tok, LexicalError>> for ParseError {
+    fn from(err: LalrpopError<Location, Tok, LexicalError>) -> Self {
+        match err {
+            // TODO: Are there cases where this isn't an EOF?
+            LalrpopError::InvalidToken { location } => ParseError {
+                error: ParseErrorType::Eof,
+                location,
+            },
+            LalrpopError::ExtraToken { token } => ParseError {
+                error: ParseErrorType::ExtraToken(token.1),
+                location: token.0,
+            },
+            LalrpopError::User { error } => ParseError {
+                error: ParseErrorType::Lexical(error.error),
+                location: error.location,
+            },
+            LalrpopError::UnrecognizedToken { token, expected } => {
+                // Hacky, but it's how CPython does it. See PyParser_AddToken,
+                // in particular "Only one possible expected token" comment.
+                let expected = (expected.len() == 1).then(|| expected[0].clone());
+                ParseError {
+                    error: ParseErrorType::UnrecognizedToken(token.1, expected),
+                    location: token.0,
+                }
+            }
+            LalrpopError::UnrecognizedEOF { location, .. } => ParseError {
+                error: ParseErrorType::Eof,
+                location,
+            },
+        }
+    }
+}
+
+impl fmt::Display for ParseError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{} at {}", self.error, self.location)
+    }
+}
+
+impl fmt::Display for ParseErrorType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            ParseErrorType::Eof => write!(f, "Got unexpected EOF"),
+            ParseErrorType::ExtraToken(ref tok) => write!(f, "Got extraneous token: {:?}", tok),
+            ParseErrorType::InvalidToken => write!(f, "Got invalid token"),
+            ParseErrorType::UnrecognizedToken(ref tok, ref expected) => {
+                if *tok == Tok::Indent {
+                    write!(f, "unexpected indent")
+                } else if expected.as_deref() == Some("Indent") {
+                    write!(f, "expected an indented block")
+                } else {
+                    write!(f, "invalid syntax. Got unexpected token {}", tok)
+                }
+            }
+            ParseErrorType::Lexical(ref error) => write!(f, "{}", error),
+        }
+    }
+}
+
+impl Error for ParseErrorType {}
+
+impl ParseErrorType {
+    pub fn is_indentation_error(&self) -> bool {
+        match self {
+            ParseErrorType::Lexical(LexicalErrorType::IndentationError) => true,
+            ParseErrorType::UnrecognizedToken(token, expected) => {
+                *token == Tok::Indent || expected.clone() == Some("Indent".to_owned())
+            }
+            _ => false,
+        }
+    }
+    pub fn is_tab_error(&self) -> bool {
+        matches!(
+            self,
+            ParseErrorType::Lexical(LexicalErrorType::TabError)
+                | ParseErrorType::Lexical(LexicalErrorType::TabsAfterSpaces)
+        )
+    }
+}
+
+impl std::ops::Deref for ParseError {
+    type Target = ParseErrorType;
+    fn deref(&self) -> &Self::Target {
+        &self.error
+    }
+}
+
+impl Error for ParseError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        None
+    }
+}