Rollup of 8 pull requests

Cargo.lock

@@ -3756,6 +3756,7 @@ dependencies = [
  "rustc_monomorphize",
  "rustc_parse",
  "rustc_passes",
+ "rustc_pattern_analysis",
  "rustc_privacy",
  "rustc_query_system",
  "rustc_resolve",
@@ -4229,6 +4230,7 @@ dependencies = [
  "rustc_infer",
  "rustc_macros",
  "rustc_middle",
+ "rustc_pattern_analysis",
  "rustc_session",
  "rustc_span",
  "rustc_target",
@@ -4364,6 +4366,26 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "rustc_pattern_analysis"
+version = "0.0.0"
+dependencies = [
+ "rustc_apfloat",
+ "rustc_arena",
+ "rustc_data_structures",
+ "rustc_errors",
+ "rustc_fluent_macro",
+ "rustc_hir",
+ "rustc_index",
+ "rustc_macros",
+ "rustc_middle",
+ "rustc_session",
+ "rustc_span",
+ "rustc_target",
+ "smallvec",
+ "tracing",
+]
+
 [[package]]
 name = "rustc_privacy"
 version = "0.0.0"

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -7,6 +7,7 @@ mod item;
 
 use crate::pp::Breaks::{Consistent, Inconsistent};
 use crate::pp::{self, Breaks};
+use crate::pprust::state::expr::FixupContext;
 use rustc_ast::attr::AttrIdGenerator;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, BinOpToken, CommentKind, Delimiter, Nonterminal, Token, TokenKind};
@@ -811,7 +812,7 @@ pub trait PrintState<'a>: std::ops::Deref<Target = pp::Printer> + std::ops::Dere
     }
 
     fn expr_to_string(&self, e: &ast::Expr) -> String {
-        Self::to_string(|s| s.print_expr(e))
+        Self::to_string(|s| s.print_expr(e, FixupContext::default()))
     }
 
     fn meta_item_lit_to_string(&self, lit: &ast::MetaItemLit) -> String {
@@ -916,7 +917,7 @@ impl<'a> State<'a> {
     }
 
     fn commasep_exprs(&mut self, b: Breaks, exprs: &[P<ast::Expr>]) {
-        self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e), |e| e.span)
+        self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e, FixupContext::default()), |e| e.span)
     }
 
     pub fn print_opt_lifetime(&mut self, lifetime: &Option<ast::Lifetime>) {
@@ -953,7 +954,7 @@ impl<'a> State<'a> {
         match generic_arg {
             GenericArg::Lifetime(lt) => self.print_lifetime(*lt),
             GenericArg::Type(ty) => self.print_type(ty),
-            GenericArg::Const(ct) => self.print_expr(&ct.value),
+            GenericArg::Const(ct) => self.print_expr(&ct.value, FixupContext::default()),
         }
     }
 
@@ -1020,12 +1021,12 @@ impl<'a> State<'a> {
                 self.word("[");
                 self.print_type(ty);
                 self.word("; ");
-                self.print_expr(&length.value);
+                self.print_expr(&length.value, FixupContext::default());
                 self.word("]");
             }
             ast::TyKind::Typeof(e) => {
                 self.word("typeof(");
-                self.print_expr(&e.value);
+                self.print_expr(&e.value, FixupContext::default());
                 self.word(")");
             }
             ast::TyKind::Infer => {
@@ -1081,7 +1082,7 @@ impl<'a> State<'a> {
                 if let Some((init, els)) = loc.kind.init_else_opt() {
                     self.nbsp();
                     self.word_space("=");
-                    self.print_expr(init);
+                    self.print_expr(init, FixupContext::default());
                     if let Some(els) = els {
                         self.cbox(INDENT_UNIT);
                         self.ibox(INDENT_UNIT);
@@ -1095,14 +1096,14 @@ impl<'a> State<'a> {
             ast::StmtKind::Item(item) => self.print_item(item),
             ast::StmtKind::Expr(expr) => {
                 self.space_if_not_bol();
-                self.print_expr_outer_attr_style(expr, false);
+                self.print_expr_outer_attr_style(expr, false, FixupContext::default());
                 if classify::expr_requires_semi_to_be_stmt(expr) {
                     self.word(";");
                 }
             }
             ast::StmtKind::Semi(expr) => {
                 self.space_if_not_bol();
-                self.print_expr_outer_attr_style(expr, false);
+                self.print_expr_outer_attr_style(expr, false, FixupContext::default());
                 self.word(";");
             }
             ast::StmtKind::Empty => {
@@ -1154,7 +1155,7 @@ impl<'a> State<'a> {
                 ast::StmtKind::Expr(expr) if i == blk.stmts.len() - 1 => {
                     self.maybe_print_comment(st.span.lo());
                     self.space_if_not_bol();
-                    self.print_expr_outer_attr_style(expr, false);
+                    self.print_expr_outer_attr_style(expr, false, FixupContext::default());
                     self.maybe_print_trailing_comment(expr.span, Some(blk.span.hi()));
                 }
                 _ => self.print_stmt(st),
@@ -1167,13 +1168,41 @@ impl<'a> State<'a> {
     }
 
     /// Print a `let pat = expr` expression.
-    fn print_let(&mut self, pat: &ast::Pat, expr: &ast::Expr) {
+    ///
+    /// Parentheses are inserted surrounding `expr` if a round-trip through the
+    /// parser would otherwise work out the wrong way in a condition position.
+    ///
+    /// For example each of the following would mean the wrong thing without
+    /// parentheses.
+    ///
+    /// ```ignore (illustrative)
+    /// if let _ = (Struct {}) {}
+    ///
+    /// if let _ = (true && false) {}
+    /// ```
+    ///
+    /// In a match guard, the second case still requires parens, but the first
+    /// case no longer does because anything until `=>` is considered part of
+    /// the match guard expression. Parsing of the expression is not terminated
+    /// by `{` in that position.
+    ///
+    /// ```ignore (illustrative)
+    /// match () {
+    ///     () if let _ = Struct {} => {}
+    ///     () if let _ = (true && false) => {}
+    /// }
+    /// ```
+    fn print_let(&mut self, pat: &ast::Pat, expr: &ast::Expr, fixup: FixupContext) {
         self.word("let ");
         self.print_pat(pat);
         self.space();
         self.word_space("=");
-        let npals = || parser::needs_par_as_let_scrutinee(expr.precedence().order());
-        self.print_expr_cond_paren(expr, Self::cond_needs_par(expr) || npals())
+        self.print_expr_cond_paren(
+            expr,
+            fixup.parenthesize_exterior_struct_lit && parser::contains_exterior_struct_lit(expr)
+                || parser::needs_par_as_let_scrutinee(expr.precedence().order()),
+            FixupContext::default(),
+        );
     }
 
     fn print_mac(&mut self, m: &ast::MacCall) {
@@ -1220,7 +1249,7 @@ impl<'a> State<'a> {
                         print_reg_or_class(s, reg);
                         s.pclose();
                         s.space();
-                        s.print_expr(expr);
+                        s.print_expr(expr, FixupContext::default());
                     }
                     InlineAsmOperand::Out { reg, late, expr } => {
                         s.word(if *late { "lateout" } else { "out" });
@@ -1229,7 +1258,7 @@ impl<'a> State<'a> {
                         s.pclose();
                         s.space();
                         match expr {
-                            Some(expr) => s.print_expr(expr),
+                            Some(expr) => s.print_expr(expr, FixupContext::default()),
                             None => s.word("_"),
                         }
                     }
@@ -1239,26 +1268,26 @@ impl<'a> State<'a> {
                         print_reg_or_class(s, reg);
                         s.pclose();
                         s.space();
-                        s.print_expr(expr);
+                        s.print_expr(expr, FixupContext::default());
                     }
                     InlineAsmOperand::SplitInOut { reg, late, in_expr, out_expr } => {
                         s.word(if *late { "inlateout" } else { "inout" });
                         s.popen();
                         print_reg_or_class(s, reg);
                         s.pclose();
                         s.space();
-                        s.print_expr(in_expr);
+                        s.print_expr(in_expr, FixupContext::default());
                         s.space();
                         s.word_space("=>");
                         match out_expr {
-                            Some(out_expr) => s.print_expr(out_expr),
+                            Some(out_expr) => s.print_expr(out_expr, FixupContext::default()),
                             None => s.word("_"),
                         }
                     }
                     InlineAsmOperand::Const { anon_const } => {
                         s.word("const");
                         s.space();
-                        s.print_expr(&anon_const.value);
+                        s.print_expr(&anon_const.value, FixupContext::default());
                     }
                     InlineAsmOperand::Sym { sym } => {
                         s.word("sym");
@@ -1452,18 +1481,18 @@ impl<'a> State<'a> {
                     self.print_pat(inner);
                 }
             }
-            PatKind::Lit(e) => self.print_expr(e),
+            PatKind::Lit(e) => self.print_expr(e, FixupContext::default()),
             PatKind::Range(begin, end, Spanned { node: end_kind, .. }) => {
                 if let Some(e) = begin {
-                    self.print_expr(e);
+                    self.print_expr(e, FixupContext::default());
                 }
                 match end_kind {
                     RangeEnd::Included(RangeSyntax::DotDotDot) => self.word("..."),
                     RangeEnd::Included(RangeSyntax::DotDotEq) => self.word("..="),
                     RangeEnd::Excluded => self.word(".."),
                 }
                 if let Some(e) = end {
-                    self.print_expr(e);
+                    self.print_expr(e, FixupContext::default());
                 }
             }
             PatKind::Slice(elts) => {
@@ -1617,7 +1646,7 @@ impl<'a> State<'a> {
                     if let Some(default) = default {
                         s.space();
                         s.word_space("=");
-                        s.print_expr(&default.value);
+                        s.print_expr(&default.value, FixupContext::default());
                     }
                 }
             }