diff options
Diffstat (limited to 'compiler/rustc_parse/src/parser/stmt.rs')
| -rw-r--r-- | compiler/rustc_parse/src/parser/stmt.rs | 427 |
1 files changed, 427 insertions, 0 deletions
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs new file mode 100644 index 00000000000..ac067cb0eab --- /dev/null +++ b/compiler/rustc_parse/src/parser/stmt.rs @@ -0,0 +1,427 @@ +use super::attr::DEFAULT_INNER_ATTR_FORBIDDEN; +use super::diagnostics::Error; +use super::expr::LhsExpr; +use super::pat::GateOr; +use super::path::PathStyle; +use super::{BlockMode, Parser, Restrictions, SemiColonMode}; +use crate::maybe_whole; + +use rustc_ast as ast; +use rustc_ast::ptr::P; +use rustc_ast::token::{self, TokenKind}; +use rustc_ast::util::classify; +use rustc_ast::{AttrStyle, AttrVec, Attribute, MacCall, MacStmtStyle}; +use rustc_ast::{Block, BlockCheckMode, Expr, ExprKind, Local, Stmt, StmtKind, DUMMY_NODE_ID}; +use rustc_errors::{Applicability, PResult}; +use rustc_span::source_map::{BytePos, Span}; +use rustc_span::symbol::{kw, sym}; + +use std::mem; + +impl<'a> Parser<'a> { + /// Parses a statement. This stops just before trailing semicolons on everything but items. + /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed. + pub(super) fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> { + Ok(self.parse_stmt_without_recovery().unwrap_or_else(|mut e| { + e.emit(); + self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore); + None + })) + } + + fn parse_stmt_without_recovery(&mut self) -> PResult<'a, Option<Stmt>> { + maybe_whole!(self, NtStmt, |x| Some(x)); + + let attrs = self.parse_outer_attributes()?; + let lo = self.token.span; + + let stmt = if self.eat_keyword(kw::Let) { + self.parse_local_mk(lo, attrs.into())? + } else if self.is_kw_followed_by_ident(kw::Mut) { + self.recover_stmt_local(lo, attrs.into(), "missing keyword", "let mut")? + } else if self.is_kw_followed_by_ident(kw::Auto) { + self.bump(); // `auto` + let msg = "write `let` instead of `auto` to introduce a new variable"; + self.recover_stmt_local(lo, attrs.into(), msg, "let")? + } else if self.is_kw_followed_by_ident(sym::var) { + self.bump(); // `var` + let msg = "write `let` instead of `var` to introduce a new variable"; + self.recover_stmt_local(lo, attrs.into(), msg, "let")? + } else if self.check_path() && !self.token.is_qpath_start() && !self.is_path_start_item() { + // We have avoided contextual keywords like `union`, items with `crate` visibility, + // or `auto trait` items. We aim to parse an arbitrary path `a::b` but not something + // that starts like a path (1 token), but it fact not a path. + // Also, we avoid stealing syntax from `parse_item_`. + self.parse_stmt_path_start(lo, attrs)? + } else if let Some(item) = self.parse_item_common(attrs.clone(), false, true, |_| true)? { + // FIXME: Bad copy of attrs + self.mk_stmt(lo.to(item.span), StmtKind::Item(P(item))) + } else if self.eat(&token::Semi) { + // Do not attempt to parse an expression if we're done here. + self.error_outer_attrs(&attrs); + self.mk_stmt(lo, StmtKind::Empty) + } else if self.token != token::CloseDelim(token::Brace) { + // Remainder are line-expr stmts. + let e = self.parse_expr_res(Restrictions::STMT_EXPR, Some(attrs.into()))?; + self.mk_stmt(lo.to(e.span), StmtKind::Expr(e)) + } else { + self.error_outer_attrs(&attrs); + return Ok(None); + }; + Ok(Some(stmt)) + } + + fn parse_stmt_path_start(&mut self, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, Stmt> { + let path = self.parse_path(PathStyle::Expr)?; + + if self.eat(&token::Not) { + return self.parse_stmt_mac(lo, attrs.into(), path); + } + + let expr = if self.check(&token::OpenDelim(token::Brace)) { + self.parse_struct_expr(path, AttrVec::new())? + } else { + let hi = self.prev_token.span; + self.mk_expr(lo.to(hi), ExprKind::Path(None, path), AttrVec::new()) + }; + + let expr = self.with_res(Restrictions::STMT_EXPR, |this| { + let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?; + this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr)) + })?; + Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Expr(expr))) + } + + /// Parses a statement macro `mac!(args)` provided a `path` representing `mac`. + /// At this point, the `!` token after the path has already been eaten. + fn parse_stmt_mac(&mut self, lo: Span, attrs: AttrVec, path: ast::Path) -> PResult<'a, Stmt> { + let args = self.parse_mac_args()?; + let delim = args.delim(); + let hi = self.prev_token.span; + + let style = + if delim == token::Brace { MacStmtStyle::Braces } else { MacStmtStyle::NoBraces }; + + let mac = MacCall { path, args, prior_type_ascription: self.last_type_ascription }; + + let kind = if delim == token::Brace || self.token == token::Semi || self.token == token::Eof + { + StmtKind::MacCall(P((mac, style, attrs))) + } else { + // Since none of the above applied, this is an expression statement macro. + let e = self.mk_expr(lo.to(hi), ExprKind::MacCall(mac), AttrVec::new()); + let e = self.maybe_recover_from_bad_qpath(e, true)?; + let e = self.parse_dot_or_call_expr_with(e, lo, attrs)?; + let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?; + StmtKind::Expr(e) + }; + Ok(self.mk_stmt(lo.to(hi), kind)) + } + + /// Error on outer attributes in this context. + /// Also error if the previous token was a doc comment. + fn error_outer_attrs(&self, attrs: &[Attribute]) { + if let [.., last] = attrs { + if last.is_doc_comment() { + self.span_fatal_err(last.span, Error::UselessDocComment).emit(); + } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) { + self.struct_span_err(last.span, "expected statement after outer attribute").emit(); + } + } + } + + fn recover_stmt_local( + &mut self, + lo: Span, + attrs: AttrVec, + msg: &str, + sugg: &str, + ) -> PResult<'a, Stmt> { + let stmt = self.parse_local_mk(lo, attrs)?; + self.struct_span_err(lo, "invalid variable declaration") + .span_suggestion(lo, msg, sugg.to_string(), Applicability::MachineApplicable) + .emit(); + Ok(stmt) + } + + fn parse_local_mk(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, Stmt> { + let local = self.parse_local(attrs)?; + Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Local(local))) + } + + /// Parses a local variable declaration. + fn parse_local(&mut self, attrs: AttrVec) -> PResult<'a, P<Local>> { + let lo = self.prev_token.span; + let pat = self.parse_top_pat(GateOr::Yes)?; + + let (err, ty) = if self.eat(&token::Colon) { + // Save the state of the parser before parsing type normally, in case there is a `:` + // instead of an `=` typo. + let parser_snapshot_before_type = self.clone(); + let colon_sp = self.prev_token.span; + match self.parse_ty() { + Ok(ty) => (None, Some(ty)), + Err(mut err) => { + if let Ok(snip) = self.span_to_snippet(pat.span) { + err.span_label(pat.span, format!("while parsing the type for `{}`", snip)); + } + let err = if self.check(&token::Eq) { + err.emit(); + None + } else { + // Rewind to before attempting to parse the type and continue parsing. + let parser_snapshot_after_type = + mem::replace(self, parser_snapshot_before_type); + Some((parser_snapshot_after_type, colon_sp, err)) + }; + (err, None) + } + } + } else { + (None, None) + }; + let init = match (self.parse_initializer(err.is_some()), err) { + (Ok(init), None) => { + // init parsed, ty parsed + init + } + (Ok(init), Some((_, colon_sp, mut err))) => { + // init parsed, ty error + // Could parse the type as if it were the initializer, it is likely there was a + // typo in the code: `:` instead of `=`. Add suggestion and emit the error. + err.span_suggestion_short( + colon_sp, + "use `=` if you meant to assign", + " =".to_string(), + Applicability::MachineApplicable, + ); + err.emit(); + // As this was parsed successfully, continue as if the code has been fixed for the + // rest of the file. It will still fail due to the emitted error, but we avoid + // extra noise. + init + } + (Err(mut init_err), Some((snapshot, _, ty_err))) => { + // init error, ty error + init_err.cancel(); + // Couldn't parse the type nor the initializer, only raise the type error and + // return to the parser state before parsing the type as the initializer. + // let x: <parse_error>; + *self = snapshot; + return Err(ty_err); + } + (Err(err), None) => { + // init error, ty parsed + // Couldn't parse the initializer and we're not attempting to recover a failed + // parse of the type, return the error. + return Err(err); + } + }; + let hi = if self.token == token::Semi { self.token.span } else { self.prev_token.span }; + Ok(P(ast::Local { ty, pat, init, id: DUMMY_NODE_ID, span: lo.to(hi), attrs })) + } + + /// Parses the RHS of a local variable declaration (e.g., '= 14;'). + fn parse_initializer(&mut self, eq_optional: bool) -> PResult<'a, Option<P<Expr>>> { + let eq_consumed = match self.token.kind { + token::BinOpEq(..) => { + // Recover `let x <op>= 1` as `let x = 1` + self.struct_span_err( + self.token.span, + "can't reassign to an uninitialized variable", + ) + .span_suggestion_short( + self.token.span, + "initialize the variable", + "=".to_string(), + Applicability::MaybeIncorrect, + ) + .emit(); + self.bump(); + true + } + _ => self.eat(&token::Eq), + }; + + Ok(if eq_consumed || eq_optional { Some(self.parse_expr()?) } else { None }) + } + + /// Parses a block. No inner attributes are allowed. + pub(super) fn parse_block(&mut self) -> PResult<'a, P<Block>> { + let (attrs, block) = self.parse_inner_attrs_and_block()?; + if let [.., last] = &*attrs { + self.error_on_forbidden_inner_attr(last.span, DEFAULT_INNER_ATTR_FORBIDDEN); + } + Ok(block) + } + + fn error_block_no_opening_brace<T>(&mut self) -> PResult<'a, T> { + let sp = self.token.span; + let tok = super::token_descr(&self.token); + let mut e = self.struct_span_err(sp, &format!("expected `{{`, found {}", tok)); + let do_not_suggest_help = self.token.is_keyword(kw::In) || self.token == token::Colon; + + // Check to see if the user has written something like + // + // if (cond) + // bar; + // + // which is valid in other languages, but not Rust. + match self.parse_stmt_without_recovery() { + // If the next token is an open brace (e.g., `if a b {`), the place- + // inside-a-block suggestion would be more likely wrong than right. + Ok(Some(_)) + if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace)) + || do_not_suggest_help => {} + Ok(Some(stmt)) => { + let stmt_own_line = self.sess.source_map().is_line_before_span_empty(sp); + let stmt_span = if stmt_own_line && self.eat(&token::Semi) { + // Expand the span to include the semicolon. + stmt.span.with_hi(self.prev_token.span.hi()) + } else { + stmt.span + }; + if let Ok(snippet) = self.span_to_snippet(stmt_span) { + e.span_suggestion( + stmt_span, + "try placing this code inside a block", + format!("{{ {} }}", snippet), + // Speculative; has been misleading in the past (#46836). + Applicability::MaybeIncorrect, + ); + } + } + Err(mut e) => { + self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore); + e.cancel(); + } + _ => {} + } + e.span_label(sp, "expected `{`"); + Err(e) + } + + /// Parses a block. Inner attributes are allowed. + pub(super) fn parse_inner_attrs_and_block( + &mut self, + ) -> PResult<'a, (Vec<Attribute>, P<Block>)> { + self.parse_block_common(self.token.span, BlockCheckMode::Default) + } + + /// Parses a block. Inner attributes are allowed. + pub(super) fn parse_block_common( + &mut self, + lo: Span, + blk_mode: BlockCheckMode, + ) -> PResult<'a, (Vec<Attribute>, P<Block>)> { + maybe_whole!(self, NtBlock, |x| (Vec::new(), x)); + + if !self.eat(&token::OpenDelim(token::Brace)) { + return self.error_block_no_opening_brace(); + } + + Ok((self.parse_inner_attributes()?, self.parse_block_tail(lo, blk_mode)?)) + } + + /// Parses the rest of a block expression or function body. + /// Precondition: already parsed the '{'. + fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> { + let mut stmts = vec![]; + while !self.eat(&token::CloseDelim(token::Brace)) { + if self.token == token::Eof { + break; + } + let stmt = match self.parse_full_stmt() { + Err(mut err) => { + self.maybe_annotate_with_ascription(&mut err, false); + err.emit(); + self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore); + Some(self.mk_stmt_err(self.token.span)) + } + Ok(stmt) => stmt, + }; + if let Some(stmt) = stmt { + stmts.push(stmt); + } else { + // Found only `;` or `}`. + continue; + }; + } + Ok(self.mk_block(stmts, s, lo.to(self.prev_token.span))) + } + + /// Parses a statement, including the trailing semicolon. + pub fn parse_full_stmt(&mut self) -> PResult<'a, Option<Stmt>> { + // Skip looking for a trailing semicolon when we have an interpolated statement. + maybe_whole!(self, NtStmt, |x| Some(x)); + + let mut stmt = match self.parse_stmt_without_recovery()? { + Some(stmt) => stmt, + None => return Ok(None), + }; + + let mut eat_semi = true; + match stmt.kind { + // Expression without semicolon. + StmtKind::Expr(ref expr) + if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) => + { + // Just check for errors and recover; do not eat semicolon yet. + if let Err(mut e) = + self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)]) + { + if let TokenKind::DocComment(..) = self.token.kind { + if let Ok(snippet) = self.span_to_snippet(self.token.span) { + let sp = self.token.span; + let marker = &snippet[..3]; + let (comment_marker, doc_comment_marker) = marker.split_at(2); + + e.span_suggestion( + sp.with_hi(sp.lo() + BytePos(marker.len() as u32)), + &format!( + "add a space before `{}` to use a regular comment", + doc_comment_marker, + ), + format!("{} {}", comment_marker, doc_comment_marker), + Applicability::MaybeIncorrect, + ); + } + } + e.emit(); + self.recover_stmt(); + // Don't complain about type errors in body tail after parse error (#57383). + let sp = expr.span.to(self.prev_token.span); + stmt.kind = StmtKind::Expr(self.mk_expr_err(sp)); + } + } + StmtKind::Local(..) => { + self.expect_semi()?; + eat_semi = false; + } + StmtKind::Empty => eat_semi = false, + _ => {} + } + + if eat_semi && self.eat(&token::Semi) { + stmt = stmt.add_trailing_semicolon(); + } + stmt.span = stmt.span.to(self.prev_token.span); + Ok(Some(stmt)) + } + + pub(super) fn mk_block(&self, stmts: Vec<Stmt>, rules: BlockCheckMode, span: Span) -> P<Block> { + P(Block { stmts, id: DUMMY_NODE_ID, rules, span }) + } + + pub(super) fn mk_stmt(&self, span: Span, kind: StmtKind) -> Stmt { + Stmt { id: DUMMY_NODE_ID, kind, span } + } + + fn mk_stmt_err(&self, span: Span) -> Stmt { + self.mk_stmt(span, StmtKind::Expr(self.mk_expr_err(span))) + } + + pub(super) fn mk_block_err(&self, span: Span) -> P<Block> { + self.mk_block(vec![self.mk_stmt_err(span)], BlockCheckMode::Default, span) + } +} |