visitor.rs

use std::cell::{Cell, RefCell};
use std::rc::Rc;

use rustc_ast::{ast, attr::HasAttrs, token::DelimToken, visit};
use rustc_span::{symbol, BytePos, Pos, Span, DUMMY_SP};

use crate::config::{BraceStyle, Config};
use crate::formatting::{
    attr::*,
    comment::{contains_comment, rewrite_comment, CodeCharKind, CommentCodeSlices},
    items::{
        format_impl, format_trait, format_trait_alias, is_mod_decl, is_use_item,
        rewrite_associated_impl_type, rewrite_extern_crate, rewrite_opaque_impl_type,
        rewrite_opaque_type, rewrite_type_alias, FnBraceStyle, FnSig, StaticParts, StructParts,
    },
    macros::{macro_style, rewrite_macro, rewrite_macro_def, MacroPosition},
    modules::{FileModMap, Module},
    report::{FormatReport, NonFormattedRange},
    rewrite::{Rewrite, RewriteContext},
    shape::{Indent, Shape},
    skip::{is_skip_attr, SkipContext},
    source_map::{LineRangeUtils, SpanUtils},
    spanned::Spanned,
    stmt::Stmt,
    syntux::session::ParseSess,
    utils::{
        self, contains_skip, count_newlines, depr_skip_annotation, format_unsafety,
        inner_attributes, last_line_contains_single_line_comment, last_line_width, mk_sp,
        ptr_vec_to_ref_vec, rewrite_ident, starts_with_newline, stmt_expr,
    },
};
use crate::result::{ErrorKind, FormatError};

/// Creates a string slice corresponding to the specified span.
pub(crate) struct SnippetProvider {
    /// A pointer to the content of the file we are formatting.
    big_snippet: Rc<String>,
    /// A position of the start of `big_snippet`, used as an offset.
    start_pos: usize,
    /// A end position of the file that this snippet lives.
    end_pos: usize,
}

impl SnippetProvider {
    pub(crate) fn span_to_snippet(&self, span: Span) -> Option<&str> {
        let start_index = span.lo().to_usize().checked_sub(self.start_pos)?;
        let end_index = span.hi().to_usize().checked_sub(self.start_pos)?;
        Some(&self.big_snippet[start_index..end_index])
    }

    pub(crate) fn is_start_span(&self, span: Span) -> bool {
        span.lo().to_usize() == self.start_pos
    }

    pub(crate) fn new(start_pos: BytePos, end_pos: BytePos, big_snippet: Rc<String>) -> Self {
        let start_pos = start_pos.to_usize();
        let end_pos = end_pos.to_usize();
        SnippetProvider {
            big_snippet,
            start_pos,
            end_pos,
        }
    }

    pub(crate) fn start_pos(&self) -> BytePos {
        BytePos::from_usize(self.start_pos)
    }
    pub(crate) fn end_pos(&self) -> BytePos {
        BytePos::from_usize(self.end_pos)
    }
}

pub(crate) struct FmtVisitor<'a> {
    parent_context: Option<&'a RewriteContext<'a>>,
    pub(crate) parse_sess: &'a ParseSess,
    pub(crate) file_mod_map: &'a FileModMap<'a>,
    pub(crate) buffer: String,
    pub(crate) last_pos: BytePos,
    // FIXME: use an RAII util or closure for indenting
    pub(crate) block_indent: Indent,
    pub(crate) config: &'a Config,
    pub(crate) is_if_else_block: bool,
    pub(crate) snippet_provider: &'a SnippetProvider,
    pub(crate) line_number: usize,
    /// List of 1-based line ranges which were annotated with skip
    /// Both bounds are inclusifs.
    pub(crate) skipped_range: Rc<RefCell<Vec<NonFormattedRange>>>,
    pub(crate) macro_rewrite_failure: bool,
    pub(crate) report: FormatReport,
    pub(crate) skip_context: SkipContext,
    /// If set to `true`, normalize number of vertical spaces on formatting missing snippets.
    pub(crate) normalize_vertical_spaces: bool,
    /// If set to `true`, we are formatting a macro definition
    pub(crate) is_macro_def: bool,
}

impl<'a> Drop for FmtVisitor<'a> {
    fn drop(&mut self) {
        if let Some(ctx) = self.parent_context {
            if self.macro_rewrite_failure {
                ctx.macro_rewrite_failure.replace(true);
            }
        }
    }
}

impl<'b, 'a: 'b> FmtVisitor<'a> {
    fn set_parent_context(&mut self, context: &'a RewriteContext<'_>) {
        self.parent_context = Some(context);
    }

    pub(crate) fn shape(&self) -> Shape {
        Shape::indented(self.block_indent, self.config)
    }

    fn next_span(&self, hi: BytePos) -> Span {
        mk_sp(self.last_pos, hi)
    }

    fn visit_stmt(&mut self, stmt: &Stmt<'_>) {
        debug!(
            "visit_stmt: {}",
            self.parse_sess.span_to_debug_info(stmt.span())
        );

        if stmt.is_empty() {
            // If the statement is empty, just skip over it. Before that, make sure any comment
            // snippet preceding the semicolon is picked up.
            let snippet = self.snippet(mk_sp(self.last_pos, stmt.span().lo()));
            let original_starts_with_newline = snippet
                .find(|c| c != ' ')
                .map_or(false, |i| starts_with_newline(&snippet[i..]));
            let snippet = snippet.trim();
            if !snippet.is_empty() {
                if original_starts_with_newline {
                    self.push_str("\n");
                }
                self.push_str(&self.block_indent.to_string(self.config));
                self.push_str(snippet);
            }

            self.last_pos = stmt.span().hi();
            return;
        }

        match stmt.as_ast_node().kind {
            ast::StmtKind::Item(ref item) => {
                self.visit_item(item, true);
                // If the item requires a trailing ";" (like `struct Foo;`), we should have already
                // handled it. Otherwise there still may be a trailing ";", but it is unnecessary.
                // Drop it by fast-forwarding the visitor to the end of the item.
                self.last_pos = stmt.span().hi();
            }
            ast::StmtKind::Local(..) | ast::StmtKind::Expr(..) | ast::StmtKind::Semi(..) => {
                let attrs = get_attrs_from_stmt(stmt.as_ast_node());
                if contains_skip(attrs) {
                    self.push_skipped_with_span(
                        attrs,
                        stmt.span(),
                        get_span_without_attrs(stmt.as_ast_node()),
                    );
                } else {
                    let shape = self.shape();
                    let rewrite = self.with_context(|ctx| stmt.rewrite(&ctx, shape));
                    self.push_rewrite(stmt.span(), rewrite)
                }
            }
            ast::StmtKind::MacCall(ref mac_stmt) => {
                if self.visit_attrs(&mac_stmt.attrs, ast::AttrStyle::Outer) {
                    self.push_skipped_with_span(
                        &mac_stmt.attrs,
                        stmt.span(),
                        get_span_without_attrs(stmt.as_ast_node()),
                    );
                } else {
                    self.visit_mac(&mac_stmt.mac, None, MacroPosition::Statement);
                }
                self.format_missing(stmt.span().hi());
            }
            ast::StmtKind::Empty => {}
        }
    }

    /// Advances the position of the visitor to the first statement or the inner attribute of a
    /// block.
    ///
    /// If `preserve_block_start_blank_lines` is true, the return value contains the newlines that
    /// should be preserved.
    pub(crate) fn advance_to_first_block_item(
        &mut self,
        first_item_pos: Option<BytePos>,
    ) -> Option<String> {
        let missing_span = first_item_pos.map(|pos| self.next_span(pos))?;
        let snippet = self.snippet(missing_span);

        let len = CommentCodeSlices::new(snippet)
            .next()
            .and_then(|(kind, _, s)| {
                if kind == CodeCharKind::Normal {
                    s.rfind('\n')
                } else {
                    None
                }
            });
        if let Some(len) = len {
            self.last_pos = self.last_pos + BytePos::from_usize(len);
        }

        if self.config.preserve_block_start_blank_lines() {
            // First we need to find the span to look for blank lines in. This is either the
            // - span between the opening brace and first item, or
            // - span between the opening brace and a comment before the first item
            // We do this so that we get a span of contiguous whitespace, which makes processing the
            // blank lines easier.
            let blank_lines_snippet = if let Some(hi) = self
                .snippet_provider
                .span_to_snippet(missing_span)
                .and_then(|s| s.find('/'))
            {
                self.snippet_provider.span_to_snippet(mk_sp(
                    missing_span.lo(),
                    missing_span.lo() + BytePos::from_usize(hi),
                ))
            } else {
                self.snippet_provider.span_to_snippet(missing_span)
            };

            if let Some(snippet) = blank_lines_snippet {
                if snippet.find('\n') != snippet.rfind('\n') {
                    let mut lines = snippet.lines().map(&str::trim);
                    lines.next(); // Eat block-opening newline
                    lines.next_back(); // Eat newline before the first item
                    let mut result = String::new();
                    while let Some("") = lines.next() {
                        result.push('\n');
                    }
                    if !result.is_empty() {
                        return Some(result);
                    }
                }
            } else {
                debug!("Failed to preserve blank lines for {:?}", missing_span);
            }
        }
        None
    }

    pub(crate) fn visit_block(
        &mut self,
        b: &ast::Block,
        inner_attrs: Option<&[ast::Attribute]>,
        has_braces: bool,
    ) {
        debug!(
            "visit_block: {}",
            self.parse_sess.span_to_debug_info(b.span),
        );

        // Check if this block has braces.
        let brace_compensation = BytePos(if has_braces { 1 } else { 0 });

        self.last_pos = self.last_pos + brace_compensation;
        self.block_indent = self.block_indent.block_indent(self.config);
        self.push_str("{");

        let first_non_ws = inner_attrs
            .and_then(|attrs| attrs.first().map(|attr| attr.span.lo()))
            .or_else(|| b.stmts.first().map(|s| s.span().lo()));
        if let Some(opening_nls) = self.advance_to_first_block_item(first_non_ws) {
            self.push_str(&opening_nls);
        }

        // Format inner attributes if available.
        if let Some(attrs) = inner_attrs {
            self.visit_attrs(attrs, ast::AttrStyle::Inner);
        }

        self.walk_block_stmts(b);

        if !b.stmts.is_empty() {
            if let Some(expr) = stmt_expr(&b.stmts[b.stmts.len() - 1]) {
                if utils::semicolon_for_expr(&self.get_context(), expr) {
                    self.push_str(";");
                }
            }
        }

        let rest_span = self.next_span(b.span.hi());
        if out_of_file_lines_range!(self, rest_span) {
            self.push_str(self.snippet(rest_span));
            self.block_indent = self.block_indent.block_unindent(self.config);
        } else {
            // Ignore the closing brace.
            let missing_span = self.next_span(b.span.hi() - brace_compensation);
            self.close_block(missing_span, self.unindent_comment_on_closing_brace(b));
        }
        self.last_pos = source!(self, b.span).hi();
    }

    fn close_block(&mut self, span: Span, unindent_comment: bool) {
        let config = self.config;

        let mut prev_kind = CodeCharKind::Normal;
        let mut newline_inserted = false;

        let skip_normal = |s: &str| {
            let trimmed = s.trim();
            !trimmed.is_empty() && trimmed.chars().all(|c| c == ';')
        };

        let last_line_offset = if last_line_contains_single_line_comment(&self.buffer) {
            0
        } else {
            last_line_width(&self.buffer) + 1
        };

        if unindent_comment {
            self.block_indent = self.block_indent.block_unindent(config);
        }

        let comment_snippet = self.snippet(span);

        let align_to_right = if unindent_comment && contains_comment(&comment_snippet) {
            let first_lines = comment_snippet.splitn(2, '/').next().unwrap_or("");
            last_line_width(first_lines) > last_line_width(&comment_snippet)
        } else {
            false
        };

        let mut iter = CommentCodeSlices::with_offset(
            comment_snippet,
            last_line_offset,
            self.config.tab_spaces(),
        )
        .peekable();
        while let Some((kind, offset, sub_slice)) = iter.next() {
            debug!("close_block: {:?} {:?} {:?}", kind, offset, sub_slice);

            match kind {
                CodeCharKind::Comment => {
                    let comment_shape = if newline_inserted {
                        self.shape().comment(self.config)
                    } else {
                        Shape {
                            width: self.config.comment_width(),
                            indent: Indent::from_width(self.config, last_line_offset),
                            offset: 0,
                        }
                    };
                    let comment_str =
                        rewrite_comment(sub_slice.trim(), false, comment_shape, config);
                    if self
                        .buffer
                        .chars()
                        .last()
                        .map_or(false, |c| !c.is_whitespace() && c != '/')
                    {
                        self.push_str(" ");
                    }
                    match comment_str {
                        Some(ref s) => self.push_str(s),
                        None => self.push_str(&sub_slice),
                    }
                }
                CodeCharKind::Normal if skip_normal(&sub_slice) => {
                    prev_kind = kind;
                    continue;
                }
                CodeCharKind::Normal => {
                    let prev_is_comment = prev_kind == CodeCharKind::Comment;
                    prev_kind = kind;

                    if iter.peek().is_none() {
                        continue;
                    }

                    match count_newlines(&sub_slice) {
                        0 if !prev_is_comment
                            || !last_line_contains_single_line_comment(&self.buffer) =>
                        {
                            self.push_str(" ");
                            continue;
                        }
                        0 => {}
                        1 if prev_is_comment
                            && last_line_contains_single_line_comment(&self.buffer) =>
                        {
                            self.push_str("\n")
                        }
                        1 => {}
                        _ => self.push_str("\n"),
                    }
                    newline_inserted = true;
                    if unindent_comment && align_to_right {
                        self.block_indent = self.block_indent.block_indent(self.config);
                    }
                    self.push_str(&self.block_indent.to_string_with_newline(config));
                    if unindent_comment && align_to_right {
                        self.block_indent = self.block_indent.block_unindent(self.config);
                    }
                }
            }
            prev_kind = kind;
        }
        if unindent_comment {
            self.block_indent = self.block_indent.block_indent(self.config);
        }
        self.block_indent = self.block_indent.block_unindent(self.config);
        self.push_str(&self.block_indent.to_string_with_newline(config));
        self.push_str("}");
    }

    fn unindent_comment_on_closing_brace(&self, b: &ast::Block) -> bool {
        self.is_if_else_block && !b.stmts.is_empty()
    }

    // Note that this only gets called for function definitions. Required methods
    // on traits do not get handled here.
    pub(crate) fn visit_fn(
        &mut self,
        fk: visit::FnKind<'_>,
        generics: &ast::Generics,
        fd: &ast::FnDecl,
        s: Span,
        defaultness: ast::Defaultness,
        inner_attrs: Option<&[ast::Attribute]>,
    ) {
        let indent = self.block_indent;
        let block;
        let rewrite = match fk {
            visit::FnKind::Fn(_, ident, _, _, Some(ref b)) => {
                block = b;
                self.rewrite_fn_before_block(
                    indent,
                    ident,
                    &FnSig::from_fn_kind(&fk, generics, fd, defaultness),
                    mk_sp(s.lo(), b.span.lo()),
                )
            }
            _ => unreachable!(),
        };

        if let Some((fn_str, fn_brace_style)) = rewrite {
            self.format_missing_with_indent(source!(self, s).lo());

            if let Some(rw) = self.single_line_fn(&fn_str, block, inner_attrs) {
                self.push_str(&rw);
                self.last_pos = s.hi();
                return;
            }

            self.push_str(&fn_str);
            match fn_brace_style {
                FnBraceStyle::SameLine => self.push_str(" "),
                FnBraceStyle::NextLine => {
                    self.push_str(&self.block_indent.to_string_with_newline(self.config))
                }
                _ => unreachable!(),
            }
            self.last_pos = source!(self, block.span).lo();
        } else {
            self.format_missing(source!(self, block.span).lo());
        }

        self.visit_block(block, inner_attrs, true)
    }

    pub(crate) fn visit_item(&mut self, item: &ast::Item, normalize_spaces: bool) {
        self.normalize_vertical_spaces = normalize_spaces;
        self.visit_item_inner(item);
    }

    fn visit_item_inner(&mut self, item: &ast::Item) {
        skip_out_of_file_lines_range_visitor!(self, item.span);

        // This is where we bail out if there is a skip attribute. This is only
        // complex in the module case. It is complex because the module could be
        // in a separate file and there might be attributes in both files, but
        // the AST lumps them all together.
        let filtered_attrs;
        let mut attrs = &item.attrs;
        let skip_context_saved = self.skip_context.clone();
        self.skip_context.update_with_attrs(&attrs);

        let should_visit_node_again = match item.kind {
            // For use/extern crate items, skip rewriting attributes but check for a skip attribute.
            ast::ItemKind::Use(..) | ast::ItemKind::ExternCrate(_) => {
                if contains_skip(attrs) {
                    self.push_skipped_with_span(attrs.as_slice(), item.span(), item.span());
                    false
                } else {
                    true
                }
            }
            // Module is inline, in this case we treat it like any other item.
            _ if !is_mod_decl(item) => {
                if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
                    self.push_skipped_with_span(item.attrs.as_slice(), item.span(), item.span());
                    false
                } else {
                    true
                }
            }
            // Module is not inline, but should be skipped.
            ast::ItemKind::Mod(..) if contains_skip(&item.attrs) => false,
            // Module is not inline and should not be skipped. We want
            // to process only the attributes in the current file.
            ast::ItemKind::Mod(..) => {
                filtered_attrs = filter_inline_attrs(&item.attrs, item.span());
                // Assert because if we should skip it should be caught by
                // the above case.
                assert!(!self.visit_attrs(&filtered_attrs, ast::AttrStyle::Outer));
                attrs = &filtered_attrs;
                true
            }
            _ => {
                if self.visit_attrs(&item.attrs, ast::AttrStyle::Outer) {
                    self.push_skipped_with_span(item.attrs.as_slice(), item.span(), item.span());
                    false
                } else {
                    true
                }
            }
        };

        if should_visit_node_again {
            match item.kind {
                ast::ItemKind::Use(ref tree) => self.format_import(item, tree),
                ast::ItemKind::Impl { .. } => {
                    let block_indent = self.block_indent;
                    let rw = self.with_context(|ctx| format_impl(&ctx, item, block_indent));
                    self.push_rewrite(item.span, rw);
                }
                ast::ItemKind::Trait(..) => {
                    let block_indent = self.block_indent;
                    let rw = self.with_context(|ctx| format_trait(&ctx, item, block_indent));
                    self.push_rewrite(item.span, rw);
                }
                ast::ItemKind::TraitAlias(ref generics, ref generic_bounds) => {
                    let shape = Shape::indented(self.block_indent, self.config);
                    let rw = format_trait_alias(
                        &self.get_context(),
                        item.ident,
                        &item.vis,
                        generics,
                        generic_bounds,
                        shape,
                    );
                    self.push_rewrite(item.span, rw);
                }
                ast::ItemKind::ExternCrate(_) => {
                    let rw = rewrite_extern_crate(&self.get_context(), item, self.shape());
                    let span = if attrs.is_empty() {
                        item.span
                    } else {
                        mk_sp(attrs[0].span.lo(), item.span.hi())
                    };
                    self.push_rewrite(span, rw);
                }
                ast::ItemKind::Struct(..) | ast::ItemKind::Union(..) => {
                    self.visit_struct(&StructParts::from_item(item));
                }
                ast::ItemKind::Enum(ref def, ref generics) => {
                    self.format_missing_with_indent(source!(self, item.span).lo());
                    self.visit_enum(item.ident, &item.vis, def, generics, item.span);
                    self.last_pos = source!(self, item.span).hi();
                }
                ast::ItemKind::Mod(ref module) => {
                    let is_inline = !is_mod_decl(item);
                    self.format_missing_with_indent(source!(self, item.span).lo());
                    self.format_mod(module, &item.vis, item.span, item.ident, attrs, is_inline);
                }
                ast::ItemKind::MacCall(ref mac) => {
                    self.visit_mac(mac, Some(item.ident), MacroPosition::Item);
                }
                ast::ItemKind::ForeignMod(ref foreign_mod) => {
                    self.format_missing_with_indent(source!(self, item.span).lo());
                    self.format_foreign_mod(foreign_mod, item.span, item.attrs());
                }
                ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
                    self.visit_static(&StaticParts::from_item(item));
                }
                ast::ItemKind::Fn(defaultness, ref fn_signature, ref generics, Some(ref body)) => {
                    let inner_attrs = inner_attributes(&item.attrs);
                    let fn_ctxt = match fn_signature.header.ext {
                        ast::Extern::None => visit::FnCtxt::Free,
                        _ => visit::FnCtxt::Foreign,
                    };
                    self.visit_fn(
                        visit::FnKind::Fn(
                            fn_ctxt,
                            item.ident,
                            &fn_signature,
                            &item.vis,
                            Some(body),
                        ),
                        generics,
                        &fn_signature.decl,
                        item.span,
                        defaultness,
                        Some(&inner_attrs),
                    )
                }
                ast::ItemKind::Fn(_, ref fn_signature, ref generics, None) => {
                    let indent = self.block_indent;
                    let rewrite = self.rewrite_required_fn(
                        indent,
                        item.ident,
                        &fn_signature,
                        generics,
                        item.span,
                    );
                    self.push_rewrite(item.span, rewrite);
                }
                ast::ItemKind::TyAlias(_, ref generics, ref generic_bounds, ref ty) => match ty {
                    Some(ty) => {
                        let rewrite = rewrite_type_alias(
                            item.ident,
                            Some(&*ty),
                            generics,
                            Some(generic_bounds),
                            &self.get_context(),
                            self.block_indent,
                            &item.vis,
                            item.span,
                        );
                        self.push_rewrite(item.span, rewrite);
                    }
                    None => {
                        let rewrite = rewrite_opaque_type(
                            &self.get_context(),
                            self.block_indent,
                            item.ident,
                            generic_bounds,
                            generics,
                            &item.vis,
                            item.span,
                        );
                        self.push_rewrite(item.span, rewrite);
                    }
                },
                ast::ItemKind::GlobalAsm(..) => {
                    let snippet = Some(self.snippet(item.span).to_owned());
                    self.push_rewrite(item.span, snippet);
                }
                ast::ItemKind::MacroDef(ref def) => {
                    let rewrite = rewrite_macro_def(
                        &self.get_context(),
                        self.shape(),
                        self.block_indent,
                        def,
                        item.ident,
                        &item.vis,
                        item.span,
                    );
                    self.push_rewrite(item.span, rewrite);
                }
            };
        }
        self.skip_context = skip_context_saved;
    }

    pub(crate) fn visit_trait_item(&mut self, ti: &ast::AssocItem) {
        skip_out_of_file_lines_range_visitor!(self, ti.span);

        if self.visit_attrs(&ti.attrs, ast::AttrStyle::Outer) {
            self.push_skipped_with_span(ti.attrs.as_slice(), ti.span, ti.span);
            return;
        }
        let skip_context_outer = self.skip_context.clone();
        self.skip_context.update_with_attrs(&ti.attrs);

        match ti.kind {
            ast::AssocItemKind::Const(..) => self.visit_static(&StaticParts::from_trait_item(ti)),
            ast::AssocItemKind::Fn(_, ref sig, ref generics, None) => {
                let indent = self.block_indent;
                let rewrite = self.rewrite_required_fn(indent, ti.ident, sig, generics, ti.span);
                self.push_rewrite(ti.span, rewrite);
            }
            ast::AssocItemKind::Fn(defaultness, ref sig, ref generics, Some(ref body)) => {
                let inner_attrs = inner_attributes(&ti.attrs);
                let vis = ast::Visibility {
                    kind: ast::VisibilityKind::Inherited,
                    span: DUMMY_SP,
                    tokens: None,
                };
                let fn_ctxt = visit::FnCtxt::Assoc(visit::AssocCtxt::Trait);
                self.visit_fn(
                    visit::FnKind::Fn(fn_ctxt, ti.ident, sig, &vis, Some(body)),
                    generics,
                    &sig.decl,
                    ti.span,
                    defaultness,
                    Some(&inner_attrs),
                );
            }
            ast::AssocItemKind::TyAlias(_, ref generics, ref generic_bounds, ref type_default) => {
                let rewrite = rewrite_type_alias(
                    ti.ident,
                    type_default.as_ref(),
                    generics,
                    Some(generic_bounds),
                    &self.get_context(),
                    self.block_indent,
                    &ti.vis,
                    ti.span,
                );
                self.push_rewrite(ti.span, rewrite);
            }
            ast::AssocItemKind::MacCall(ref mac) => {
                self.visit_mac(mac, Some(ti.ident), MacroPosition::Item);
            }
        }
        self.skip_context = skip_context_outer;
    }

    pub(crate) fn visit_impl_item(&mut self, ii: &ast::AssocItem) {
        skip_out_of_file_lines_range_visitor!(self, ii.span);

        if self.visit_attrs(&ii.attrs, ast::AttrStyle::Outer) {
            self.push_skipped_with_span(ii.attrs.as_slice(), ii.span, ii.span);
            return;
        }
        let skip_context_outer = self.skip_context.clone();
        self.skip_context.update_with_attrs(&ii.attrs);

        match ii.kind {
            ast::AssocItemKind::Fn(defaultness, ref sig, ref generics, Some(ref body)) => {
                let inner_attrs = inner_attributes(&ii.attrs);
                let fn_ctxt = visit::FnCtxt::Assoc(visit::AssocCtxt::Impl);
                self.visit_fn(
                    visit::FnKind::Fn(fn_ctxt, ii.ident, sig, &ii.vis, Some(body)),
                    generics,
                    &sig.decl,
                    ii.span,
                    defaultness,
                    Some(&inner_attrs),
                );
            }
            ast::AssocItemKind::Fn(_, ref sig, ref generics, None) => {
                let indent = self.block_indent;
                let rewrite = self.rewrite_required_fn(indent, ii.ident, sig, generics, ii.span);
                self.push_rewrite(ii.span, rewrite);
            }
            ast::AssocItemKind::Const(..) => self.visit_static(&StaticParts::from_impl_item(ii)),
            ast::AssocItemKind::TyAlias(defaultness, ref generics, _, ref ty) => {
                let rewrite_associated = || {
                    rewrite_associated_impl_type(
                        ii.ident,
                        &ii.vis,
                        defaultness,
                        ty.as_ref(),
                        generics,
                        &self.get_context(),
                        self.block_indent,
                        ii.span,
                    )
                };
                let rewrite = match ty {
                    None => rewrite_associated(),
                    Some(ty) => match ty.kind {
                        ast::TyKind::ImplTrait(_, ref bounds) => rewrite_opaque_impl_type(
                            &self.get_context(),
                            ii.ident,
                            generics,
                            bounds,
                            self.block_indent,
                        ),
                        _ => rewrite_associated(),
                    },
                };
                self.push_rewrite(ii.span, rewrite);
            }
            ast::AssocItemKind::MacCall(ref mac) => {
                self.visit_mac(mac, Some(ii.ident), MacroPosition::Item);
            }
        }
        self.skip_context = skip_context_outer;
    }

    fn visit_mac(&mut self, mac: &ast::MacCall, ident: Option<symbol::Ident>, pos: MacroPosition) {
        skip_out_of_file_lines_range_visitor!(self, mac.span());

        // 1 = ;
        let shape = self.shape().saturating_sub_width(1);
        let rewrite = self.with_context(|ctx| rewrite_macro(mac, ident, ctx, shape, pos));
        // As of v638 of the rustc-ap-* crates, the associated span no longer includes
        // the trailing semicolon. This determines the correct span to ensure scenarios
        // with whitespace between the delimiters and trailing semi (i.e. `foo!(abc)     ;`)
        // are formatted correctly.
        let (span, rewrite) = match macro_style(mac, &self.get_context()) {
            DelimToken::Bracket | DelimToken::Paren if MacroPosition::Item == pos => {
                let search_span = mk_sp(mac.span().hi(), self.snippet_provider.end_pos());
                let hi = self.snippet_provider.span_before(search_span, ";");
                let target_span = mk_sp(mac.span().lo(), hi + BytePos(1));
                let rewrite = rewrite.map(|rw| {
                    if !rw.ends_with(';') {
                        format!("{};", rw)
                    } else {
                        rw
                    }
                });
                (target_span, rewrite)
            }
            _ => (mac.span(), rewrite),
        };

        self.push_rewrite(span, rewrite);
    }

    pub(crate) fn push_str(&mut self, s: &str) {
        self.line_number += count_newlines(s);
        self.buffer.push_str(s);
    }

    #[allow(clippy::needless_pass_by_value)]
    fn push_rewrite_inner(&mut self, span: Span, rewrite: Option<String>) {
        if let Some(ref s) = rewrite {
            self.push_str(s);
        } else {
            let snippet = self.snippet(span);
            self.push_str(snippet.trim());
        }
        self.last_pos = source!(self, span).hi();
    }

    pub(crate) fn push_rewrite(&mut self, span: Span, rewrite: Option<String>) {
        self.format_missing_with_indent(source!(self, span).lo());
        self.push_rewrite_inner(span, rewrite);
    }

    pub(crate) fn push_skipped_with_span(
        &mut self,
        attrs: &[ast::Attribute],
        item_span: Span,
        main_span: Span,
    ) {
        self.format_missing_with_indent(source!(self, item_span).lo());
        // do not take into account the lines with attributes as part of the skipped range
        let attrs_end = attrs
            .iter()
            .map(|attr| self.parse_sess.line_of_byte_pos(attr.span.hi()))
            .max()
            .unwrap_or(1);
        let first_line = self.parse_sess.line_of_byte_pos(main_span.lo());
        // Statement can start after some newlines and/or spaces
        // or it can be on the same line as the last attribute.
        // So here we need to take a minimum between the two.
        let lo = std::cmp::min(attrs_end + 1, first_line);
        self.push_rewrite_inner(item_span, None);
        let hi = self.line_number + 1;
        self.skipped_range
            .borrow_mut()
            .push(NonFormattedRange::new(lo, hi));
    }

    pub(crate) fn from_context(ctx: &'a RewriteContext<'_>) -> FmtVisitor<'a> {
        let mut visitor = FmtVisitor::from_parse_sess(
            ctx.parse_sess,
            ctx.config,
            ctx.snippet_provider,
            ctx.file_mod_map,
            ctx.report.clone(),
        );
        visitor.skip_context.update(ctx.skip_context.clone());
        visitor.set_parent_context(ctx);
        visitor
    }

    pub(crate) fn from_parse_sess(
        parse_session: &'a ParseSess,
        config: &'a Config,
        snippet_provider: &'a SnippetProvider,
        file_mod_map: &'a FileModMap<'_>,
        report: FormatReport,
    ) -> FmtVisitor<'a> {
        FmtVisitor {
            parent_context: None,
            file_mod_map,
            parse_sess: parse_session,
            buffer: String::with_capacity(snippet_provider.big_snippet.len() * 2),
            last_pos: BytePos(0),
            block_indent: Indent::empty(),
            config,
            is_if_else_block: false,
            snippet_provider,
            line_number: 0,
            skipped_range: Rc::new(RefCell::new(vec![])),
            macro_rewrite_failure: false,
            report,
            skip_context: Default::default(),
            normalize_vertical_spaces: false,
            is_macro_def: false,
        }
    }

    pub(crate) fn opt_snippet(&'b self, span: Span) -> Option<&'a str> {
        self.snippet_provider.span_to_snippet(span)
    }

    pub(crate) fn snippet(&'b self, span: Span) -> &'a str {
        self.opt_snippet(span).unwrap()
    }

    pub(crate) fn is_start_span(&'b self, span: Span) -> bool {
        self.snippet_provider.is_start_span(span)
    }

    // Returns true if we should skip the following item.
    pub(crate) fn visit_attrs(&mut self, attrs: &[ast::Attribute], style: ast::AttrStyle) -> bool {
        for attr in attrs {
            if attr.has_name(depr_skip_annotation()) {
                let file_name = self.parse_sess.span_to_filename(attr.span);
                self.report.add_format_error(
                    file_name,
                    FormatError::from_span(ErrorKind::DeprecatedAttr, self.parse_sess, attr.span),
                );
            } else {
                match &attr.kind {
                    ast::AttrKind::Normal(ref attribute_item)
                        if self.is_unknown_rustfmt_attr(&attribute_item.path.segments) =>
                    {
                        let file_name = self.parse_sess.span_to_filename(attr.span);
                        self.report.add_format_error(
                            file_name,
                            FormatError::from_span(ErrorKind::BadAttr, self.parse_sess, attr.span),
                        );
                    }
                    _ => {}
                }
            }
        }
        if contains_skip(attrs) {
            return true;
        }

        let attrs: Vec<_> = attrs.iter().filter(|a| a.style == style).cloned().collect();
        if attrs.is_empty() {
            return false;
        }

        let rewrite = attrs.rewrite(&self.get_context(), self.shape());
        let span = mk_sp(attrs[0].span.lo(), attrs[attrs.len() - 1].span.hi());
        self.push_rewrite(span, rewrite);

        false
    }

    fn is_unknown_rustfmt_attr(&self, segments: &[ast::PathSegment]) -> bool {
        if segments[0].ident.to_string() != "rustfmt" {
            return false;
        }
        !is_skip_attr(segments)
    }

    fn walk_mod_items(&mut self, m: &ast::Mod) {
        self.visit_items_with_reordering(&ptr_vec_to_ref_vec(&m.items));
    }

    fn walk_stmts(&mut self, stmts: &[Stmt<'_>]) {
        if stmts.is_empty() {
            return;
        }

        // Extract leading `use ...;`.
        let items: Vec<_> = stmts
            .iter()
            .take_while(|stmt| stmt.to_item().map_or(false, is_use_item))
            .filter_map(|stmt| stmt.to_item())
            .collect();

        if items.is_empty() {
            self.visit_stmt(&stmts[0]);
            self.walk_stmts(&stmts[1..]);
        } else {
            self.visit_items_with_reordering(&items);
            self.walk_stmts(&stmts[items.len()..]);
        }
    }

    fn walk_block_stmts(&mut self, b: &ast::Block) {
        self.walk_stmts(&Stmt::from_ast_nodes(b.stmts.iter()))
    }

    fn format_mod(
        &mut self,
        m: &ast::Mod,
        vis: &ast::Visibility,
        s: Span,
        ident: symbol::Ident,
        attrs: &[ast::Attribute],
        is_internal: bool,
    ) {
        let vis_str = utils::format_visibility(&self.get_context(), vis);
        self.push_str(&*vis_str);
        self.push_str(format_unsafety(m.unsafety));
        self.push_str("mod ");
        // Calling `to_owned()` to work around borrow checker.
        let ident_str = rewrite_ident(&self.get_context(), ident).to_owned();
        self.push_str(&ident_str);

        if is_internal {
            match self.config.brace_style() {
                BraceStyle::AlwaysNextLine => {
                    let indent_str = self.block_indent.to_string_with_newline(self.config);
                    self.push_str(&indent_str);
                    self.push_str("{");
                }
                _ => self.push_str(" {"),
            }
            // Hackery to account for the closing }.
            let mod_lo = self.snippet_provider.span_after(source!(self, s), "{");
            let body_snippet =
                self.snippet(mk_sp(mod_lo, source!(self, m.inner).hi() - BytePos(1)));
            let body_snippet = body_snippet.trim();
            if body_snippet.is_empty() {
                self.push_str("}");
            } else {
                self.last_pos = mod_lo;
                self.block_indent = self.block_indent.block_indent(self.config);

                let first_non_ws = inner_attributes(attrs)
                    .first()
                    .map(|attr| attr.span.lo())
                    .or_else(|| m.items.first().map(|s| s.span().lo()));
                if let Some(opening_nls) = self.advance_to_first_block_item(first_non_ws) {
                    self.push_str(&opening_nls);
                    if attrs.is_empty() {
                        self.push_str("\n");
                    }
                }

                self.visit_attrs(attrs, ast::AttrStyle::Inner);
                self.walk_mod_items(m);
                let missing_span = self.next_span(m.inner.hi() - BytePos(1));
                self.close_block(missing_span, false);
            }
            self.last_pos = source!(self, m.inner).hi();
        } else {
            self.push_str(";");
            self.last_pos = source!(self, s).hi();
        }
    }

    pub(crate) fn format_separate_mod(&mut self, m: &Module<'_>, end_pos: BytePos) {
        self.block_indent = Indent::empty();
        let skipped = self.visit_attrs(m.attrs(), ast::AttrStyle::Inner);
        assert!(
            !skipped,
            "Skipping module must be handled before reaching this line.",
        );

        self.walk_mod_items(m.as_ref());
        self.format_missing_with_indent(end_pos);
    }

    pub(crate) fn skip_empty_lines(&mut self, end_pos: BytePos) {
        while let Some(pos) = self
            .snippet_provider
            .opt_span_after(self.next_span(end_pos), "\n")
        {
            if let Some(snippet) = self.opt_snippet(self.next_span(pos)) {
                if snippet.trim().is_empty() {
                    self.last_pos = pos;
                } else {
                    return;
                }
            }
        }
    }

    pub(crate) fn with_context<F>(&mut self, f: F) -> Option<String>
    where
        F: Fn(&RewriteContext<'_>) -> Option<String>,
    {
        let context = self.get_context();
        let result = f(&context);

        self.macro_rewrite_failure |= context.macro_rewrite_failure.get();
        result
    }

    pub(crate) fn get_context(&self) -> RewriteContext<'_> {
        RewriteContext {
            parse_sess: self.parse_sess,
            file_mod_map: self.file_mod_map,
            config: self.config,
            inside_macro: Rc::new(Cell::new(false)),
            use_block: Cell::new(false),
            is_if_else_block: Cell::new(false),
            force_one_line_chain: Cell::new(false),
            snippet_provider: self.snippet_provider,
            macro_rewrite_failure: Cell::new(false),
            report: self.report.clone(),
            skip_context: self.skip_context.clone(),
            skipped_range: self.skipped_range.clone(),
            is_macro_def: self.is_macro_def,
        }
    }
}