1 files changed, 303 insertions, 0 deletions

diff --git a/crates/syntax/src/validation.rs b/crates/syntax/src/validation.rs
new file mode 100644
index 000000000..2dddaf09a
--- /dev/null
+++ b/crates/syntax/src/validation.rs
@@ -0,0 +1,303 @@
+//! FIXME: write short doc here
+
+mod block;
+
+use crate::{
+    ast, match_ast, AstNode, SyntaxError,
+    SyntaxKind::{BYTE, BYTE_STRING, CHAR, CONST, FN, INT_NUMBER, STRING, TYPE_ALIAS},
+    SyntaxNode, SyntaxToken, TextSize, T,
+};
+use rustc_lexer::unescape::{
+    self, unescape_byte, unescape_byte_literal, unescape_char, unescape_literal, Mode,
+};
+use std::convert::TryFrom;
+
+fn rustc_unescape_error_to_string(err: unescape::EscapeError) -> &'static str {
+    use unescape::EscapeError as EE;
+
+    #[rustfmt::skip]
+    let err_message = match err {
+        EE::ZeroChars => {
+            "Literal must not be empty"
+        }
+        EE::MoreThanOneChar => {
+            "Literal must be one character long"
+        }
+        EE::LoneSlash => {
+            "Character must be escaped: `\\`"
+        }
+        EE::InvalidEscape => {
+            "Invalid escape"
+        }
+        EE::BareCarriageReturn | EE::BareCarriageReturnInRawString => {
+            "Character must be escaped: `\r`"
+        }
+        EE::EscapeOnlyChar => {
+            "Escape character `\\` must be escaped itself"
+        }
+        EE::TooShortHexEscape => {
+            "ASCII hex escape code must have exactly two digits"
+        }
+        EE::InvalidCharInHexEscape => {
+            "ASCII hex escape code must contain only hex characters"
+        }
+        EE::OutOfRangeHexEscape => {
+            "ASCII hex escape code must be at most 0x7F"
+        }
+        EE::NoBraceInUnicodeEscape => {
+            "Missing `{` to begin the unicode escape"
+        }
+        EE::InvalidCharInUnicodeEscape => {
+            "Unicode escape must contain only hex characters and underscores"
+        }
+        EE::EmptyUnicodeEscape => {
+            "Unicode escape must not be empty"
+        }
+        EE::UnclosedUnicodeEscape => {
+            "Missing `}` to terminate the unicode escape"
+        }
+        EE::LeadingUnderscoreUnicodeEscape => {
+            "Unicode escape code must not begin with an underscore"
+        }
+        EE::OverlongUnicodeEscape => {
+            "Unicode escape code must have at most 6 digits"
+        }
+        EE::LoneSurrogateUnicodeEscape => {
+            "Unicode escape code must not be a surrogate"
+        }
+        EE::OutOfRangeUnicodeEscape => {
+            "Unicode escape code must be at most 0x10FFFF"
+        }
+        EE::UnicodeEscapeInByte => {
+            "Byte literals must not contain unicode escapes"
+        }
+        EE::NonAsciiCharInByte | EE::NonAsciiCharInByteString => {
+            "Byte literals must not contain non-ASCII characters"
+        }
+    };
+
+    err_message
+}
+
+pub(crate) fn validate(root: &SyntaxNode) -> Vec<SyntaxError> {
+    // FIXME:
+    // * Add unescape validation of raw string literals and raw byte string literals
+    // * Add validation of doc comments are being attached to nodes
+
+    let mut errors = Vec::new();
+    for node in root.descendants() {
+        match_ast! {
+            match node {
+                ast::Literal(it) => validate_literal(it, &mut errors),
+                ast::BlockExpr(it) => block::validate_block_expr(it, &mut errors),
+                ast::FieldExpr(it) => validate_numeric_name(it.name_ref(), &mut errors),
+                ast::RecordExprField(it) => validate_numeric_name(it.name_ref(), &mut errors),
+                ast::Visibility(it) => validate_visibility(it, &mut errors),
+                ast::RangeExpr(it) => validate_range_expr(it, &mut errors),
+                ast::PathSegment(it) => validate_path_keywords(it, &mut errors),
+                _ => (),
+            }
+        }
+    }
+    errors
+}
+
+fn validate_literal(literal: ast::Literal, acc: &mut Vec<SyntaxError>) {
+    // FIXME: move this function to outer scope (https://github.com/rust-analyzer/rust-analyzer/pull/2834#discussion_r366196658)
+    fn unquote(text: &str, prefix_len: usize, end_delimiter: char) -> Option<&str> {
+        text.rfind(end_delimiter).and_then(|end| text.get(prefix_len..end))
+    }
+
+    let token = literal.token();
+    let text = token.text().as_str();
+
+    // FIXME: lift this lambda refactor to `fn` (https://github.com/rust-analyzer/rust-analyzer/pull/2834#discussion_r366199205)
+    let mut push_err = |prefix_len, (off, err): (usize, unescape::EscapeError)| {
+        let off = token.text_range().start() + TextSize::try_from(off + prefix_len).unwrap();
+        acc.push(SyntaxError::new_at_offset(rustc_unescape_error_to_string(err), off));
+    };
+
+    match token.kind() {
+        BYTE => {
+            if let Some(Err(e)) = unquote(text, 2, '\'').map(unescape_byte) {
+                push_err(2, e);
+            }
+        }
+        CHAR => {
+            if let Some(Err(e)) = unquote(text, 1, '\'').map(unescape_char) {
+                push_err(1, e);
+            }
+        }
+        BYTE_STRING => {
+            if let Some(without_quotes) = unquote(text, 2, '"') {
+                unescape_byte_literal(without_quotes, Mode::ByteStr, &mut |range, char| {
+                    if let Err(err) = char {
+                        push_err(2, (range.start, err));
+                    }
+                })
+            }
+        }
+        STRING => {
+            if let Some(without_quotes) = unquote(text, 1, '"') {
+                unescape_literal(without_quotes, Mode::Str, &mut |range, char| {
+                    if let Err(err) = char {
+                        push_err(1, (range.start, err));
+                    }
+                })
+            }
+        }
+        _ => (),
+    }
+}
+
+pub(crate) fn validate_block_structure(root: &SyntaxNode) {
+    let mut stack = Vec::new();
+    for node in root.descendants() {
+        match node.kind() {
+            T!['{'] => stack.push(node),
+            T!['}'] => {
+                if let Some(pair) = stack.pop() {
+                    assert_eq!(
+                        node.parent(),
+                        pair.parent(),
+                        "\nunpaired curleys:\n{}\n{:#?}\n",
+                        root.text(),
+                        root,
+                    );
+                    assert!(
+                        node.next_sibling().is_none() && pair.prev_sibling().is_none(),
+                        "\nfloating curlys at {:?}\nfile:\n{}\nerror:\n{}\n",
+                        node,
+                        root.text(),
+                        node.text(),
+                    );
+                }
+            }
+            _ => (),
+        }
+    }
+}
+
+fn validate_numeric_name(name_ref: Option<ast::NameRef>, errors: &mut Vec<SyntaxError>) {
+    if let Some(int_token) = int_token(name_ref) {
+        if int_token.text().chars().any(|c| !c.is_digit(10)) {
+            errors.push(SyntaxError::new(
+                "Tuple (struct) field access is only allowed through \
+                decimal integers with no underscores or suffix",
+                int_token.text_range(),
+            ));
+        }
+    }
+
+    fn int_token(name_ref: Option<ast::NameRef>) -> Option<SyntaxToken> {
+        name_ref?.syntax().first_child_or_token()?.into_token().filter(|it| it.kind() == INT_NUMBER)
+    }
+}
+
+fn validate_visibility(vis: ast::Visibility, errors: &mut Vec<SyntaxError>) {
+    let parent = match vis.syntax().parent() {
+        Some(it) => it,
+        None => return,
+    };
+    match parent.kind() {
+        FN | CONST | TYPE_ALIAS => (),
+        _ => return,
+    }
+
+    let impl_def = match parent.parent().and_then(|it| it.parent()).and_then(ast::Impl::cast) {
+        Some(it) => it,
+        None => return,
+    };
+    if impl_def.trait_().is_some() {
+        errors.push(SyntaxError::new("Unnecessary visibility qualifier", vis.syntax.text_range()));
+    }
+}
+
+fn validate_range_expr(expr: ast::RangeExpr, errors: &mut Vec<SyntaxError>) {
+    if expr.op_kind() == Some(ast::RangeOp::Inclusive) && expr.end().is_none() {
+        errors.push(SyntaxError::new(
+            "An inclusive range must have an end expression",
+            expr.syntax().text_range(),
+        ));
+    }
+}
+
+fn validate_path_keywords(segment: ast::PathSegment, errors: &mut Vec<SyntaxError>) {
+    use ast::PathSegmentKind;
+
+    let path = segment.parent_path();
+    let is_path_start = segment.coloncolon_token().is_none() && path.qualifier().is_none();
+
+    if let Some(token) = segment.self_token() {
+        if !is_path_start {
+            errors.push(SyntaxError::new(
+                "The `self` keyword is only allowed as the first segment of a path",
+                token.text_range(),
+            ));
+        }
+    } else if let Some(token) = segment.crate_token() {
+        if !is_path_start || use_prefix(path).is_some() {
+            errors.push(SyntaxError::new(
+                "The `crate` keyword is only allowed as the first segment of a path",
+                token.text_range(),
+            ));
+        }
+    } else if let Some(token) = segment.super_token() {
+        if !all_supers(&path) {
+            errors.push(SyntaxError::new(
+                "The `super` keyword may only be preceded by other `super`s",
+                token.text_range(),
+            ));
+            return;
+        }
+
+        let mut curr_path = path;
+        while let Some(prefix) = use_prefix(curr_path) {
+            if !all_supers(&prefix) {
+                errors.push(SyntaxError::new(
+                    "The `super` keyword may only be preceded by other `super`s",
+                    token.text_range(),
+                ));
+                return;
+            }
+            curr_path = prefix;
+        }
+    }
+
+    fn use_prefix(mut path: ast::Path) -> Option<ast::Path> {
+        for node in path.syntax().ancestors().skip(1) {
+            match_ast! {
+                match node {
+                    ast::UseTree(it) => if let Some(tree_path) = it.path() {
+                        // Even a top-level path exists within a `UseTree` so we must explicitly
+                        // allow our path but disallow anything else
+                        if tree_path != path {
+                            return Some(tree_path);
+                        }
+                    },
+                    ast::UseTreeList(_it) => continue,
+                    ast::Path(parent) => path = parent,
+                    _ => return None,
+                }
+            };
+        }
+        return None;
+    }
+
+    fn all_supers(path: &ast::Path) -> bool {
+        let segment = match path.segment() {
+            Some(it) => it,
+            None => return false,
+        };
+
+        if segment.kind() != Some(PathSegmentKind::SuperKw) {
+            return false;
+        }
+
+        if let Some(ref subpath) = path.qualifier() {
+            return all_supers(subpath);
+        }
+
+        return true;
+    }
+}