Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1010 insertions, 0 deletions

diff --git a/src/tools/rustfmt/src/visitor.rs b/src/tools/rustfmt/src/visitor.rs
new file mode 100644
index 000000000..9a0e0752c
--- /dev/null
+++ b/src/tools/rustfmt/src/visitor.rs
@@ -0,0 +1,1010 @@
+use std::cell::{Cell, RefCell};
+use std::rc::Rc;
+
+use rustc_ast::{ast, token::Delimiter, visit};
+use rustc_data_structures::sync::Lrc;
+use rustc_span::{symbol, BytePos, Pos, Span};
+
+use crate::attr::*;
+use crate::comment::{contains_comment, rewrite_comment, CodeCharKind, CommentCodeSlices};
+use crate::config::Version;
+use crate::config::{BraceStyle, Config};
+use crate::coverage::transform_missing_snippet;
+use crate::items::{
+    format_impl, format_trait, format_trait_alias, is_mod_decl, is_use_item, rewrite_extern_crate,
+    rewrite_type_alias, FnBraceStyle, FnSig, ItemVisitorKind, StaticParts, StructParts,
+};
+use crate::macros::{macro_style, rewrite_macro, rewrite_macro_def, MacroPosition};
+use crate::modules::Module;
+use crate::parse::session::ParseSess;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::{Indent, Shape};
+use crate::skip::{is_skip_attr, SkipContext};
+use crate::source_map::{LineRangeUtils, SpanUtils};
+use crate::spanned::Spanned;
+use crate::stmt::Stmt;
+use crate::utils::{
+    self, contains_skip, count_newlines, depr_skip_annotation, format_unsafety, inner_attributes,
+    last_line_width, mk_sp, ptr_vec_to_ref_vec, rewrite_ident, starts_with_newline, stmt_expr,
+};
+use crate::{ErrorKind, FormatReport, FormattingError};
+
+/// 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: Lrc<String>,
+    /// A position of the start of `big_snippet`, used as an offset.
+    start_pos: usize,
+    /// An 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 new(start_pos: BytePos, end_pos: BytePos, big_snippet: Lrc<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 entire_snippet(&self) -> &str {
+        self.big_snippet.as_str()
+    }
+
+    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) 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<(usize, usize)>>>,
+    pub(crate) macro_rewrite_failure: bool,
+    pub(crate) report: FormatReport,
+    pub(crate) skip_context: SkipContext,
+    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<'_>, include_empty_semi: bool) {
+        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() {
+                // FIXME(calebcartwright 2021-01-03) - This exists strictly to maintain legacy
+                // formatting where rustfmt would preserve redundant semicolons on Items in a
+                // statement position.
+                // See comment within `walk_stmts` for more info
+                if include_empty_semi {
+                    self.format_missing(stmt.span().hi());
+                } else {
+                    if original_starts_with_newline {
+                        self.push_str("\n");
+                    }
+
+                    self.push_str(&self.block_indent.to_string(self.config));
+                    self.push_str(snippet);
+                }
+            } else if include_empty_semi {
+                self.push_str(";");
+            }
+            self.last_pos = stmt.span().hi();
+            return;
+        }
+
+        match stmt.as_ast_node().kind {
+            ast::StmtKind::Item(ref item) => {
+                self.visit_item(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 => (),
+        }
+    }
+
+    /// Remove spaces between the opening brace and the first statement or the inner attribute
+    /// of the block.
+    fn trim_spaces_after_opening_brace(
+        &mut self,
+        b: &ast::Block,
+        inner_attrs: Option<&[ast::Attribute]>,
+    ) {
+        if let Some(first_stmt) = b.stmts.first() {
+            let hi = inner_attrs
+                .and_then(|attrs| inner_attributes(attrs).first().map(|attr| attr.span.lo()))
+                .unwrap_or_else(|| first_stmt.span().lo());
+            let missing_span = self.next_span(hi);
+            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);
+            }
+        }
+    }
+
+    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("{");
+        self.trim_spaces_after_opening_brace(b, inner_attrs);
+
+        // 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 last_hi = span.lo();
+        let mut unindented = false;
+        let mut prev_ends_with_newline = false;
+        let mut extra_newline = false;
+
+        let skip_normal = |s: &str| {
+            let trimmed = s.trim();
+            trimmed.is_empty() || trimmed.chars().all(|c| c == ';')
+        };
+
+        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
+        };
+
+        for (kind, offset, sub_slice) in CommentCodeSlices::new(comment_snippet) {
+            let sub_slice = transform_missing_snippet(config, sub_slice);
+
+            debug!("close_block: {:?} {:?} {:?}", kind, offset, sub_slice);
+
+            match kind {
+                CodeCharKind::Comment => {
+                    if !unindented && unindent_comment && !align_to_right {
+                        unindented = true;
+                        self.block_indent = self.block_indent.block_unindent(config);
+                    }
+                    let span_in_between = mk_sp(last_hi, span.lo() + BytePos::from_usize(offset));
+                    let snippet_in_between = self.snippet(span_in_between);
+                    let mut comment_on_same_line = !snippet_in_between.contains('\n');
+
+                    let mut comment_shape =
+                        Shape::indented(self.block_indent, config).comment(config);
+                    if self.config.version() == Version::Two && comment_on_same_line {
+                        self.push_str(" ");
+                        // put the first line of the comment on the same line as the
+                        // block's last line
+                        match sub_slice.find('\n') {
+                            None => {
+                                self.push_str(&sub_slice);
+                            }
+                            Some(offset) if offset + 1 == sub_slice.len() => {
+                                self.push_str(&sub_slice[..offset]);
+                            }
+                            Some(offset) => {
+                                let first_line = &sub_slice[..offset];
+                                self.push_str(first_line);
+                                self.push_str(&self.block_indent.to_string_with_newline(config));
+
+                                // put the other lines below it, shaping it as needed
+                                let other_lines = &sub_slice[offset + 1..];
+                                let comment_str =
+                                    rewrite_comment(other_lines, false, comment_shape, config);
+                                match comment_str {
+                                    Some(ref s) => self.push_str(s),
+                                    None => self.push_str(other_lines),
+                                }
+                            }
+                        }
+                    } else {
+                        if comment_on_same_line {
+                            // 1 = a space before `//`
+                            let offset_len = 1 + last_line_width(&self.buffer)
+                                .saturating_sub(self.block_indent.width());
+                            match comment_shape
+                                .visual_indent(offset_len)
+                                .sub_width(offset_len)
+                            {
+                                Some(shp) => comment_shape = shp,
+                                None => comment_on_same_line = false,
+                            }
+                        };
+
+                        if comment_on_same_line {
+                            self.push_str(" ");
+                        } else {
+                            if count_newlines(snippet_in_between) >= 2 || extra_newline {
+                                self.push_str("\n");
+                            }
+                            self.push_str(&self.block_indent.to_string_with_newline(config));
+                        }
+
+                        let comment_str = rewrite_comment(&sub_slice, false, comment_shape, config);
+                        match comment_str {
+                            Some(ref s) => self.push_str(s),
+                            None => self.push_str(&sub_slice),
+                        }
+                    }
+                }
+                CodeCharKind::Normal if skip_normal(&sub_slice) => {
+                    extra_newline = prev_ends_with_newline && sub_slice.contains('\n');
+                    continue;
+                }
+                CodeCharKind::Normal => {
+                    self.push_str(&self.block_indent.to_string_with_newline(config));
+                    self.push_str(sub_slice.trim());
+                }
+            }
+            prev_ends_with_newline = sub_slice.ends_with('\n');
+            extra_newline = false;
+            last_hi = span.lo() + BytePos::from_usize(offset + sub_slice.len());
+        }
+        if unindented {
+            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<'_>,
+        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, 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) {
+        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
+                }
+            }
+        };
+
+        // TODO(calebcartwright): consider enabling box_patterns feature gate
+        if should_visit_node_again {
+            match item.kind {
+                ast::ItemKind::Use(ref tree) => self.format_import(item, tree),
+                ast::ItemKind::Impl(ref iimpl) => {
+                    let block_indent = self.block_indent;
+                    let rw = self.with_context(|ctx| format_impl(ctx, item, iimpl, 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(unsafety, ref mod_kind) => {
+                    self.format_missing_with_indent(source!(self, item.span).lo());
+                    self.format_mod(mod_kind, unsafety, &item.vis, item.span, item.ident, attrs);
+                }
+                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);
+                }
+                ast::ItemKind::Static(..) | ast::ItemKind::Const(..) => {
+                    self.visit_static(&StaticParts::from_item(item));
+                }
+                ast::ItemKind::Fn(ref fn_kind) => {
+                    let ast::Fn {
+                        defaultness,
+                        ref sig,
+                        ref generics,
+                        ref body,
+                    } = **fn_kind;
+                    if let Some(ref body) = body {
+                        let inner_attrs = inner_attributes(&item.attrs);
+                        let fn_ctxt = match sig.header.ext {
+                            ast::Extern::None => visit::FnCtxt::Free,
+                            _ => visit::FnCtxt::Foreign,
+                        };
+                        self.visit_fn(
+                            visit::FnKind::Fn(
+                                fn_ctxt,
+                                item.ident,
+                                sig,
+                                &item.vis,
+                                generics,
+                                Some(body),
+                            ),
+                            &sig.decl,
+                            item.span,
+                            defaultness,
+                            Some(&inner_attrs),
+                        )
+                    } else {
+                        let indent = self.block_indent;
+                        let rewrite = self.rewrite_required_fn(
+                            indent, item.ident, sig, &item.vis, generics, item.span,
+                        );
+                        self.push_rewrite(item.span, rewrite);
+                    }
+                }
+                ast::ItemKind::TyAlias(ref ty_alias) => {
+                    use ItemVisitorKind::Item;
+                    self.visit_ty_alias_kind(ty_alias, &Item(item), item.span);
+                }
+                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;
+    }
+
+    fn visit_ty_alias_kind(
+        &mut self,
+        ty_kind: &ast::TyAlias,
+        visitor_kind: &ItemVisitorKind<'_>,
+        span: Span,
+    ) {
+        let rewrite = rewrite_type_alias(
+            ty_kind,
+            &self.get_context(),
+            self.block_indent,
+            visitor_kind,
+            span,
+        );
+        self.push_rewrite(span, rewrite);
+    }
+
+    fn visit_assoc_item(&mut self, visitor_kind: &ItemVisitorKind<'_>) {
+        use ItemVisitorKind::*;
+        // TODO(calebcartwright): Not sure the skip spans are correct
+        let (ai, skip_span, assoc_ctxt) = match visitor_kind {
+            AssocTraitItem(ai) => (*ai, ai.span(), visit::AssocCtxt::Trait),
+            AssocImplItem(ai) => (*ai, ai.span, visit::AssocCtxt::Impl),
+            _ => unreachable!(),
+        };
+        skip_out_of_file_lines_range_visitor!(self, ai.span);
+
+        if self.visit_attrs(&ai.attrs, ast::AttrStyle::Outer) {
+            self.push_skipped_with_span(ai.attrs.as_slice(), skip_span, skip_span);
+            return;
+        }
+
+        // TODO(calebcartwright): consider enabling box_patterns feature gate
+        match (&ai.kind, visitor_kind) {
+            (ast::AssocItemKind::Const(..), AssocTraitItem(_)) => {
+                self.visit_static(&StaticParts::from_trait_item(ai))
+            }
+            (ast::AssocItemKind::Const(..), AssocImplItem(_)) => {
+                self.visit_static(&StaticParts::from_impl_item(ai))
+            }
+            (ast::AssocItemKind::Fn(ref fn_kind), _) => {
+                let ast::Fn {
+                    defaultness,
+                    ref sig,
+                    ref generics,
+                    ref body,
+                } = **fn_kind;
+                if let Some(ref body) = body {
+                    let inner_attrs = inner_attributes(&ai.attrs);
+                    let fn_ctxt = visit::FnCtxt::Assoc(assoc_ctxt);
+                    self.visit_fn(
+                        visit::FnKind::Fn(fn_ctxt, ai.ident, sig, &ai.vis, generics, Some(body)),
+                        &sig.decl,
+                        ai.span,
+                        defaultness,
+                        Some(&inner_attrs),
+                    );
+                } else {
+                    let indent = self.block_indent;
+                    let rewrite =
+                        self.rewrite_required_fn(indent, ai.ident, sig, &ai.vis, generics, ai.span);
+                    self.push_rewrite(ai.span, rewrite);
+                }
+            }
+            (ast::AssocItemKind::TyAlias(ref ty_alias), _) => {
+                self.visit_ty_alias_kind(ty_alias, visitor_kind, ai.span);
+            }
+            (ast::AssocItemKind::MacCall(ref mac), _) => {
+                self.visit_mac(mac, Some(ai.ident), MacroPosition::Item);
+            }
+            _ => unreachable!(),
+        }
+    }
+
+    pub(crate) fn visit_trait_item(&mut self, ti: &ast::AssocItem) {
+        self.visit_assoc_item(&ItemVisitorKind::AssocTraitItem(ti));
+    }
+
+    pub(crate) fn visit_impl_item(&mut self, ii: &ast::AssocItem) {
+        self.visit_assoc_item(&ItemVisitorKind::AssocImplItem(ii));
+    }
+
+    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()) {
+            Delimiter::Bracket | Delimiter::Parenthesis 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((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.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,
+        report: FormatReport,
+    ) -> FmtVisitor<'a> {
+        FmtVisitor {
+            parent_context: None,
+            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![])),
+            is_macro_def: false,
+            macro_rewrite_failure: false,
+            report,
+            skip_context: Default::default(),
+        }
+    }
+
+    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()
+    }
+
+    // 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.append(
+                    file_name,
+                    vec![FormattingError::from_span(
+                        attr.span,
+                        self.parse_sess,
+                        ErrorKind::DeprecatedAttr,
+                    )],
+                );
+            } 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.append(
+                            file_name,
+                            vec![FormattingError::from_span(
+                                attr.span,
+                                self.parse_sess,
+                                ErrorKind::BadAttr,
+                            )],
+                        );
+                    }
+                    _ => (),
+                }
+            }
+        }
+        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, items: &[rustc_ast::ptr::P<ast::Item>]) {
+        self.visit_items_with_reordering(&ptr_vec_to_ref_vec(items));
+    }
+
+    fn walk_stmts(&mut self, stmts: &[Stmt<'_>], include_current_empty_semi: bool) {
+        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], include_current_empty_semi);
+
+            // FIXME(calebcartwright 2021-01-03) - This exists strictly to maintain legacy
+            // formatting where rustfmt would preserve redundant semicolons on Items in a
+            // statement position.
+            //
+            // Starting in rustc-ap-* v692 (~2020-12-01) the rustc parser now parses this as
+            // two separate statements (Item and Empty kinds), whereas before it was parsed as
+            // a single statement with the statement's span including the redundant semicolon.
+            //
+            // rustfmt typically tosses unnecessary/redundant semicolons, and eventually we
+            // should toss these as well, but doing so at this time would
+            // break the Stability Guarantee
+            // N.B. This could be updated to utilize the version gates.
+            let include_next_empty = if stmts.len() > 1 {
+                matches!(
+                    (&stmts[0].as_ast_node().kind, &stmts[1].as_ast_node().kind),
+                    (ast::StmtKind::Item(_), ast::StmtKind::Empty)
+                )
+            } else {
+                false
+            };
+
+            self.walk_stmts(&stmts[1..], include_next_empty);
+        } else {
+            self.visit_items_with_reordering(&items);
+            self.walk_stmts(&stmts[items.len()..], false);
+        }
+    }
+
+    fn walk_block_stmts(&mut self, b: &ast::Block) {
+        self.walk_stmts(&Stmt::from_ast_nodes(b.stmts.iter()), false)
+    }
+
+    fn format_mod(
+        &mut self,
+        mod_kind: &ast::ModKind,
+        unsafety: ast::Unsafe,
+        vis: &ast::Visibility,
+        s: Span,
+        ident: symbol::Ident,
+        attrs: &[ast::Attribute],
+    ) {
+        let vis_str = utils::format_visibility(&self.get_context(), vis);
+        self.push_str(&*vis_str);
+        self.push_str(format_unsafety(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 let ast::ModKind::Loaded(ref items, ast::Inline::Yes, ref spans) = mod_kind {
+            let ast::ModSpans {
+                inner_span,
+                inject_use_span: _,
+            } = *spans;
+            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, inner_span).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);
+                self.visit_attrs(attrs, ast::AttrStyle::Inner);
+                self.walk_mod_items(items);
+                let missing_span = self.next_span(inner_span.hi() - BytePos(1));
+                self.close_block(missing_span, false);
+            }
+            self.last_pos = source!(self, inner_span).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.items);
+        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,
+            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),
+            is_macro_def: self.is_macro_def,
+            report: self.report.clone(),
+            skip_context: self.skip_context.clone(),
+            skipped_range: self.skipped_range.clone(),
+        }
+    }
+}