--- /dev/null
+use rustc_ast::{ast, ptr};
+use rustc_span::Span;
+
+use crate::attr::get_attrs_from_stmt;
+use crate::config::lists::*;
+use crate::config::Version;
+use crate::expr::{block_contains_comment, is_simple_block, is_unsafe_block, rewrite_cond};
+use crate::items::{span_hi_for_param, span_lo_for_param};
+use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
+use crate::overflow::OverflowableItem;
+use crate::rewrite::{Rewrite, RewriteContext};
+use crate::shape::Shape;
+use crate::source_map::SpanUtils;
+use crate::utils::{last_line_width, left_most_sub_expr, stmt_expr, NodeIdExt};
+
+// This module is pretty messy because of the rules around closures and blocks:
+// FIXME - the below is probably no longer true in full.
+// * if there is a return type, then there must be braces,
+// * given a closure with braces, whether that is parsed to give an inner block
+// or not depends on if there is a return type and if there are statements
+// in that block,
+// * if the first expression in the body ends with a block (i.e., is a
+// statement without needing a semi-colon), then adding or removing braces
+// can change whether it is treated as an expression or statement.
+
+pub(crate) fn rewrite_closure(
+ capture: ast::CaptureBy,
+ is_async: &ast::Async,
+ movability: ast::Movability,
+ fn_decl: &ast::FnDecl,
+ body: &ast::Expr,
+ span: Span,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+) -> Option<String> {
+ debug!("rewrite_closure {:?}", body);
+
+ let (prefix, extra_offset) = rewrite_closure_fn_decl(
+ capture, is_async, movability, fn_decl, body, span, context, shape,
+ )?;
+ // 1 = space between `|...|` and body.
+ let body_shape = shape.offset_left(extra_offset)?;
+
+ if let ast::ExprKind::Block(ref block, _) = body.kind {
+ // The body of the closure is an empty block.
+ if block.stmts.is_empty() && !block_contains_comment(context, block) {
+ return body
+ .rewrite(context, shape)
+ .map(|s| format!("{} {}", prefix, s));
+ }
+
+ let result = match fn_decl.output {
+ ast::FnRetTy::Default(_) if !context.inside_macro() => {
+ try_rewrite_without_block(body, &prefix, context, shape, body_shape)
+ }
+ _ => None,
+ };
+
+ result.or_else(|| {
+ // Either we require a block, or tried without and failed.
+ rewrite_closure_block(block, &prefix, context, body_shape)
+ })
+ } else {
+ rewrite_closure_expr(body, &prefix, context, body_shape).or_else(|| {
+ // The closure originally had a non-block expression, but we can't fit on
+ // one line, so we'll insert a block.
+ rewrite_closure_with_block(body, &prefix, context, body_shape)
+ })
+ }
+}
+
+fn try_rewrite_without_block(
+ expr: &ast::Expr,
+ prefix: &str,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+ body_shape: Shape,
+) -> Option<String> {
+ let expr = get_inner_expr(expr, prefix, context);
+
+ if is_block_closure_forced(context, expr) {
+ rewrite_closure_with_block(expr, prefix, context, shape)
+ } else {
+ rewrite_closure_expr(expr, prefix, context, body_shape)
+ }
+}
+
+fn get_inner_expr<'a>(
+ expr: &'a ast::Expr,
+ prefix: &str,
+ context: &RewriteContext<'_>,
+) -> &'a ast::Expr {
+ if let ast::ExprKind::Block(ref block, _) = expr.kind {
+ if !needs_block(block, prefix, context) {
+ // block.stmts.len() == 1 except with `|| {{}}`;
+ // https://github.com/rust-lang/rustfmt/issues/3844
+ if let Some(expr) = block.stmts.first().and_then(stmt_expr) {
+ return get_inner_expr(expr, prefix, context);
+ }
+ }
+ }
+
+ expr
+}
+
+// Figure out if a block is necessary.
+fn needs_block(block: &ast::Block, prefix: &str, context: &RewriteContext<'_>) -> bool {
+ let has_attributes = block.stmts.first().map_or(false, |first_stmt| {
+ !get_attrs_from_stmt(first_stmt).is_empty()
+ });
+
+ is_unsafe_block(block)
+ || block.stmts.len() > 1
+ || has_attributes
+ || block_contains_comment(context, block)
+ || prefix.contains('\n')
+}
+
+fn veto_block(e: &ast::Expr) -> bool {
+ match e.kind {
+ ast::ExprKind::Call(..)
+ | ast::ExprKind::Binary(..)
+ | ast::ExprKind::Cast(..)
+ | ast::ExprKind::Type(..)
+ | ast::ExprKind::Assign(..)
+ | ast::ExprKind::AssignOp(..)
+ | ast::ExprKind::Field(..)
+ | ast::ExprKind::Index(..)
+ | ast::ExprKind::Range(..)
+ | ast::ExprKind::Try(..) => true,
+ _ => false,
+ }
+}
+
+// Rewrite closure with a single expression wrapping its body with block.
+// || { #[attr] foo() } -> Block { #[attr] foo() }
+fn rewrite_closure_with_block(
+ body: &ast::Expr,
+ prefix: &str,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+) -> Option<String> {
+ let left_most = left_most_sub_expr(body);
+ let veto_block = veto_block(body) && !expr_requires_semi_to_be_stmt(left_most);
+ if veto_block {
+ return None;
+ }
+
+ let block = ast::Block {
+ stmts: vec![ast::Stmt {
+ id: ast::NodeId::root(),
+ kind: ast::StmtKind::Expr(ptr::P(body.clone())),
+ span: body.span,
+ }],
+ id: ast::NodeId::root(),
+ rules: ast::BlockCheckMode::Default,
+ tokens: None,
+ span: body
+ .attrs
+ .first()
+ .map(|attr| attr.span.to(body.span))
+ .unwrap_or(body.span),
+ };
+ let block = crate::expr::rewrite_block_with_visitor(
+ context,
+ "",
+ &block,
+ Some(&body.attrs),
+ None,
+ shape,
+ false,
+ )?;
+ Some(format!("{} {}", prefix, block))
+}
+
+// Rewrite closure with a single expression without wrapping its body with block.
+fn rewrite_closure_expr(
+ expr: &ast::Expr,
+ prefix: &str,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+) -> Option<String> {
+ fn allow_multi_line(expr: &ast::Expr) -> bool {
+ match expr.kind {
+ ast::ExprKind::Match(..)
+ | ast::ExprKind::Async(..)
+ | ast::ExprKind::Block(..)
+ | ast::ExprKind::TryBlock(..)
+ | ast::ExprKind::Loop(..)
+ | ast::ExprKind::Struct(..) => true,
+
+ ast::ExprKind::AddrOf(_, _, ref expr)
+ | ast::ExprKind::Box(ref expr)
+ | ast::ExprKind::Try(ref expr)
+ | ast::ExprKind::Unary(_, ref expr)
+ | ast::ExprKind::Cast(ref expr, _) => allow_multi_line(expr),
+
+ _ => false,
+ }
+ }
+
+ // When rewriting closure's body without block, we require it to fit in a single line
+ // unless it is a block-like expression or we are inside macro call.
+ let veto_multiline = (!allow_multi_line(expr) && !context.inside_macro())
+ || context.config.force_multiline_blocks();
+ expr.rewrite(context, shape)
+ .and_then(|rw| {
+ if veto_multiline && rw.contains('\n') {
+ None
+ } else {
+ Some(rw)
+ }
+ })
+ .map(|rw| format!("{} {}", prefix, rw))
+}
+
+// Rewrite closure whose body is block.
+fn rewrite_closure_block(
+ block: &ast::Block,
+ prefix: &str,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+) -> Option<String> {
+ Some(format!("{} {}", prefix, block.rewrite(context, shape)?))
+}
+
+// Return type is (prefix, extra_offset)
+fn rewrite_closure_fn_decl(
+ capture: ast::CaptureBy,
+ asyncness: &ast::Async,
+ movability: ast::Movability,
+ fn_decl: &ast::FnDecl,
+ body: &ast::Expr,
+ span: Span,
+ context: &RewriteContext<'_>,
+ shape: Shape,
+) -> Option<(String, usize)> {
+ let is_async = if asyncness.is_async() { "async " } else { "" };
+ let mover = if capture == ast::CaptureBy::Value {
+ "move "
+ } else {
+ ""
+ };
+ let immovable = if movability == ast::Movability::Static {
+ "static "
+ } else {
+ ""
+ };
+ // 4 = "|| {".len(), which is overconservative when the closure consists of
+ // a single expression.
+ let nested_shape = shape
+ .shrink_left(is_async.len() + mover.len() + immovable.len())?
+ .sub_width(4)?;
+
+ // 1 = |
+ let param_offset = nested_shape.indent + 1;
+ let param_shape = nested_shape.offset_left(1)?.visual_indent(0);
+ let ret_str = fn_decl.output.rewrite(context, param_shape)?;
+
+ let param_items = itemize_list(
+ context.snippet_provider,
+ fn_decl.inputs.iter(),
+ "|",
+ ",",
+ |param| span_lo_for_param(param),
+ |param| span_hi_for_param(context, param),
+ |param| param.rewrite(context, param_shape),
+ context.snippet_provider.span_after(span, "|"),
+ body.span.lo(),
+ false,
+ );
+ let item_vec = param_items.collect::<Vec<_>>();
+ // 1 = space between parameters and return type.
+ let horizontal_budget = nested_shape.width.saturating_sub(ret_str.len() + 1);
+ let tactic = definitive_tactic(
+ &item_vec,
+ ListTactic::HorizontalVertical,
+ Separator::Comma,
+ horizontal_budget,
+ );
+ let param_shape = match tactic {
+ DefinitiveListTactic::Horizontal => param_shape.sub_width(ret_str.len() + 1)?,
+ _ => param_shape,
+ };
+
+ let fmt = ListFormatting::new(param_shape, context.config)
+ .tactic(tactic)
+ .preserve_newline(true);
+ let list_str = write_list(&item_vec, &fmt)?;
+ let mut prefix = format!("{}{}{}|{}|", is_async, immovable, mover, list_str);
+
+ if !ret_str.is_empty() {
+ if prefix.contains('\n') {
+ prefix.push('\n');
+ prefix.push_str(¶m_offset.to_string(context.config));
+ } else {
+ prefix.push(' ');
+ }
+ prefix.push_str(&ret_str);
+ }
+ // 1 = space between `|...|` and body.
+ let extra_offset = last_line_width(&prefix) + 1;
+
+ Some((prefix, extra_offset))
+}
+
+// Rewriting closure which is placed at the end of the function call's arg.
+// Returns `None` if the reformatted closure 'looks bad'.
+pub(crate) fn rewrite_last_closure(
+ context: &RewriteContext<'_>,
+ expr: &ast::Expr,
+ shape: Shape,
+) -> Option<String> {
+ if let ast::ExprKind::Closure(capture, ref is_async, movability, ref fn_decl, ref body, _) =
+ expr.kind
+ {
+ let body = match body.kind {
+ ast::ExprKind::Block(ref block, _)
+ if !is_unsafe_block(block)
+ && !context.inside_macro()
+ && is_simple_block(context, block, Some(&body.attrs)) =>
+ {
+ stmt_expr(&block.stmts[0]).unwrap_or(body)
+ }
+ _ => body,
+ };
+ let (prefix, extra_offset) = rewrite_closure_fn_decl(
+ capture, is_async, movability, fn_decl, body, expr.span, context, shape,
+ )?;
+ // If the closure goes multi line before its body, do not overflow the closure.
+ if prefix.contains('\n') {
+ return None;
+ }
+
+ let body_shape = shape.offset_left(extra_offset)?;
+
+ // We force to use block for the body of the closure for certain kinds of expressions.
+ if is_block_closure_forced(context, body) {
+ return rewrite_closure_with_block(body, &prefix, context, body_shape).and_then(
+ |body_str| {
+ match fn_decl.output {
+ ast::FnRetTy::Default(..) if body_str.lines().count() <= 7 => {
+ // If the expression can fit in a single line, we need not force block
+ // closure. However, if the closure has a return type, then we must
+ // keep the blocks.
+ match rewrite_closure_expr(body, &prefix, context, shape) {
+ Some(ref single_line_body_str)
+ if !single_line_body_str.contains('\n') =>
+ {
+ Some(single_line_body_str.clone())
+ }
+ _ => Some(body_str),
+ }
+ }
+ _ => Some(body_str),
+ }
+ },
+ );
+ }
+
+ // When overflowing the closure which consists of a single control flow expression,
+ // force to use block if its condition uses multi line.
+ let is_multi_lined_cond = rewrite_cond(context, body, body_shape).map_or(false, |cond| {
+ cond.contains('\n') || cond.len() > body_shape.width
+ });
+ if is_multi_lined_cond {
+ return rewrite_closure_with_block(body, &prefix, context, body_shape);
+ }
+
+ // Seems fine, just format the closure in usual manner.
+ return expr.rewrite(context, shape);
+ }
+ None
+}
+
+/// Returns `true` if the given vector of arguments has more than one `ast::ExprKind::Closure`.
+pub(crate) fn args_have_many_closure(args: &[OverflowableItem<'_>]) -> bool {
+ args.iter()
+ .filter_map(OverflowableItem::to_expr)
+ .filter(|expr| match expr.kind {
+ ast::ExprKind::Closure(..) => true,
+ _ => false,
+ })
+ .count()
+ > 1
+}
+
+fn is_block_closure_forced(context: &RewriteContext<'_>, expr: &ast::Expr) -> bool {
+ // If we are inside macro, we do not want to add or remove block from closure body.
+ if context.inside_macro() {
+ false
+ } else {
+ is_block_closure_forced_inner(expr, context.config.version())
+ }
+}
+
+fn is_block_closure_forced_inner(expr: &ast::Expr, version: Version) -> bool {
+ match expr.kind {
+ ast::ExprKind::If(..) | ast::ExprKind::While(..) | ast::ExprKind::ForLoop(..) => true,
+ ast::ExprKind::Loop(..) if version == Version::Two => true,
+ ast::ExprKind::AddrOf(_, _, ref expr)
+ | ast::ExprKind::Box(ref expr)
+ | ast::ExprKind::Try(ref expr)
+ | ast::ExprKind::Unary(_, ref expr)
+ | ast::ExprKind::Cast(ref expr, _) => is_block_closure_forced_inner(expr, version),
+ _ => false,
+ }
+}
+
+/// Does this expression require a semicolon to be treated
+/// as a statement? The negation of this: 'can this expression
+/// be used as a statement without a semicolon' -- is used
+/// as an early-bail-out in the parser so that, for instance,
+/// if true {...} else {...}
+/// |x| 5
+/// isn't parsed as (if true {...} else {...} | x) | 5
+// From https://github.com/rust-lang/rust/blob/master/src/libsyntax/parse/classify.rs.
+fn expr_requires_semi_to_be_stmt(e: &ast::Expr) -> bool {
+ match e.kind {
+ ast::ExprKind::If(..)
+ | ast::ExprKind::Match(..)
+ | ast::ExprKind::Block(..)
+ | ast::ExprKind::While(..)
+ | ast::ExprKind::Loop(..)
+ | ast::ExprKind::ForLoop(..)
+ | ast::ExprKind::TryBlock(..) => false,
+ _ => true,
+ }
+}
projects / rustc.git / blobdiff