Introduce `AssocOp::Binary`.

It mirrors `ExprKind::Binary`, and contains a `BinOpKind`. This makes
`AssocOp` more like `ExprKind`. Note that the variants removed from
`AssocOp` are all named differently to `BinOpToken`, e.g. `Multiply`
instead of `Mul`, so that's an inconsistency removed.

The commit adds `precedence` and `fixity` methods to `BinOpKind`, and
calls them from the corresponding methods in `AssocOp`. This avoids the
need to create an `AssocOp` from a `BinOpKind` in a bunch of places, and
`AssocOp::from_ast_binop` is removed.

`AssocOp::to_ast_binop` is also no longer needed.

Overall things are shorter and nicer.

2 files changed, 74 insertions, 143 deletions

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 29c1d34a125..65dd0a34aec 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -39,7 +39,7 @@ pub use crate::format::*;
 use crate::ptr::P;
 use crate::token::{self, CommentKind, Delimiter};
 use crate::tokenstream::{DelimSpan, LazyAttrTokenStream, TokenStream};
-use crate::util::parser::{AssocOp, ExprPrecedence};
+use crate::util::parser::{ExprPrecedence, Fixity};
 
 /// A "Label" is an identifier of some point in sources,
 /// e.g. in the following code:
@@ -937,8 +937,37 @@ impl BinOpKind {
         matches!(self, BinOpKind::And | BinOpKind::Or)
     }
 
+    pub fn precedence(&self) -> ExprPrecedence {
+        use BinOpKind::*;
+        match *self {
+            Mul | Div | Rem => ExprPrecedence::Product,
+            Add | Sub => ExprPrecedence::Sum,
+            Shl | Shr => ExprPrecedence::Shift,
+            BitAnd => ExprPrecedence::BitAnd,
+            BitXor => ExprPrecedence::BitXor,
+            BitOr => ExprPrecedence::BitOr,
+            Lt | Gt | Le | Ge | Eq | Ne => ExprPrecedence::Compare,
+            And => ExprPrecedence::LAnd,
+            Or => ExprPrecedence::LOr,
+        }
+    }
+
+    pub fn fixity(&self) -> Fixity {
+        use BinOpKind::*;
+        match self {
+            Eq | Ne | Lt | Le | Gt | Ge => Fixity::None,
+            Add | Sub | Mul | Div | Rem | And | Or | BitXor | BitAnd | BitOr | Shl | Shr => {
+                Fixity::Left
+            }
+        }
+    }
+
     pub fn is_comparison(self) -> bool {
-        crate::util::parser::AssocOp::from_ast_binop(self).is_comparison()
+        use BinOpKind::*;
+        match self {
+            Eq | Ne | Lt | Le | Gt | Ge => true,
+            Add | Sub | Mul | Div | Rem | And | Or | BitXor | BitAnd | BitOr | Shl | Shr => false,
+        }
     }
 
     /// Returns `true` if the binary operator takes its arguments by value.
@@ -1332,7 +1361,7 @@ impl Expr {
             ExprKind::Range(..) => ExprPrecedence::Range,
 
             // Binop-like expr kinds, handled by `AssocOp`.
-            ExprKind::Binary(op, ..) => AssocOp::from_ast_binop(op.node).precedence(),
+            ExprKind::Binary(op, ..) => op.node.precedence(),
             ExprKind::Cast(..) => ExprPrecedence::Cast,
 
             ExprKind::Assign(..) |
diff --git a/compiler/rustc_ast/src/util/parser.rs b/compiler/rustc_ast/src/util/parser.rs
index 69df9ff93b4..e7c26aa3092 100644
--- a/compiler/rustc_ast/src/util/parser.rs
+++ b/compiler/rustc_ast/src/util/parser.rs
@@ -3,51 +3,15 @@ use rustc_span::kw;
 use crate::ast::{self, BinOpKind};
 use crate::token::{self, BinOpToken, Token};
 
-/// Associative operator with precedence.
-///
-/// This is the enum which specifies operator precedence and fixity to the parser.
+/// Associative operator.
 #[derive(Copy, Clone, PartialEq, Debug)]
 pub enum AssocOp {
-    /// `+`
-    Add,
-    /// `-`
-    Subtract,
-    /// `*`
-    Multiply,
-    /// `/`
-    Divide,
-    /// `%`
-    Modulus,
-    /// `&&`
-    LAnd,
-    /// `||`
-    LOr,
-    /// `^`
-    BitXor,
-    /// `&`
-    BitAnd,
-    /// `|`
-    BitOr,
-    /// `<<`
-    ShiftLeft,
-    /// `>>`
-    ShiftRight,
-    /// `==`
-    Equal,
-    /// `<`
-    Less,
-    /// `<=`
-    LessEqual,
-    /// `!=`
-    NotEqual,
-    /// `>`
-    Greater,
-    /// `>=`
-    GreaterEqual,
-    /// `=`
-    Assign,
+    /// A binary op.
+    Binary(BinOpKind),
     /// `?=` where ? is one of the assignable BinOps
     AssignOp(BinOpKind),
+    /// `=`
+    Assign,
     /// `as`
     As,
     /// `..` range
@@ -67,11 +31,21 @@ pub enum Fixity {
 }
 
 impl AssocOp {
-    /// Creates a new AssocOP from a token
+    /// Creates a new AssocOp from a token.
     pub fn from_token(t: &Token) -> Option<AssocOp> {
         use AssocOp::*;
         match t.kind {
             token::Eq => Some(Assign),
+            token::BinOp(BinOpToken::Plus) => Some(Binary(BinOpKind::Add)),
+            token::BinOp(BinOpToken::Minus) => Some(Binary(BinOpKind::Sub)),
+            token::BinOp(BinOpToken::Star) => Some(Binary(BinOpKind::Mul)),
+            token::BinOp(BinOpToken::Slash) => Some(Binary(BinOpKind::Div)),
+            token::BinOp(BinOpToken::Percent) => Some(Binary(BinOpKind::Rem)),
+            token::BinOp(BinOpToken::Caret) => Some(Binary(BinOpKind::BitXor)),
+            token::BinOp(BinOpToken::And) => Some(Binary(BinOpKind::BitAnd)),
+            token::BinOp(BinOpToken::Or) => Some(Binary(BinOpKind::BitOr)),
+            token::BinOp(BinOpToken::Shl) => Some(Binary(BinOpKind::Shl)),
+            token::BinOp(BinOpToken::Shr) => Some(Binary(BinOpKind::Shr)),
             token::BinOpEq(BinOpToken::Plus) => Some(AssignOp(BinOpKind::Add)),
             token::BinOpEq(BinOpToken::Minus) => Some(AssignOp(BinOpKind::Sub)),
             token::BinOpEq(BinOpToken::Star) => Some(AssignOp(BinOpKind::Mul)),
@@ -82,74 +56,31 @@ impl AssocOp {
             token::BinOpEq(BinOpToken::Or) => Some(AssignOp(BinOpKind::BitOr)),
             token::BinOpEq(BinOpToken::Shl) => Some(AssignOp(BinOpKind::Shl)),
             token::BinOpEq(BinOpToken::Shr) => Some(AssignOp(BinOpKind::Shr)),
-            token::BinOp(BinOpToken::Plus) => Some(Add),
-            token::BinOp(BinOpToken::Minus) => Some(Subtract),
-            token::BinOp(BinOpToken::Star) => Some(Multiply),
-            token::BinOp(BinOpToken::Slash) => Some(Divide),
-            token::BinOp(BinOpToken::Percent) => Some(Modulus),
-            token::BinOp(BinOpToken::Caret) => Some(BitXor),
-            token::BinOp(BinOpToken::And) => Some(BitAnd),
-            token::BinOp(BinOpToken::Or) => Some(BitOr),
-            token::BinOp(BinOpToken::Shl) => Some(ShiftLeft),
-            token::BinOp(BinOpToken::Shr) => Some(ShiftRight),
-            token::Lt => Some(Less),
-            token::Le => Some(LessEqual),
-            token::Ge => Some(GreaterEqual),
-            token::Gt => Some(Greater),
-            token::EqEq => Some(Equal),
-            token::Ne => Some(NotEqual),
-            token::AndAnd => Some(LAnd),
-            token::OrOr => Some(LOr),
+            token::Lt => Some(Binary(BinOpKind::Lt)),
+            token::Le => Some(Binary(BinOpKind::Le)),
+            token::Ge => Some(Binary(BinOpKind::Ge)),
+            token::Gt => Some(Binary(BinOpKind::Gt)),
+            token::EqEq => Some(Binary(BinOpKind::Eq)),
+            token::Ne => Some(Binary(BinOpKind::Ne)),
+            token::AndAnd => Some(Binary(BinOpKind::And)),
+            token::OrOr => Some(Binary(BinOpKind::Or)),
             token::DotDot => Some(DotDot),
             token::DotDotEq => Some(DotDotEq),
             // DotDotDot is no longer supported, but we need some way to display the error
             token::DotDotDot => Some(DotDotEq),
             // `<-` should probably be `< -`
-            token::LArrow => Some(Less),
+            token::LArrow => Some(Binary(BinOpKind::Lt)),
             _ if t.is_keyword(kw::As) => Some(As),
             _ => None,
         }
     }
 
-    /// Creates a new AssocOp from ast::BinOpKind.
-    pub fn from_ast_binop(op: BinOpKind) -> Self {
-        use AssocOp::*;
-        match op {
-            BinOpKind::Lt => Less,
-            BinOpKind::Gt => Greater,
-            BinOpKind::Le => LessEqual,
-            BinOpKind::Ge => GreaterEqual,
-            BinOpKind::Eq => Equal,
-            BinOpKind::Ne => NotEqual,
-            BinOpKind::Mul => Multiply,
-            BinOpKind::Div => Divide,
-            BinOpKind::Rem => Modulus,
-            BinOpKind::Add => Add,
-            BinOpKind::Sub => Subtract,
-            BinOpKind::Shl => ShiftLeft,
-            BinOpKind::Shr => ShiftRight,
-            BinOpKind::BitAnd => BitAnd,
-            BinOpKind::BitXor => BitXor,
-            BinOpKind::BitOr => BitOr,
-            BinOpKind::And => LAnd,
-            BinOpKind::Or => LOr,
-        }
-    }
-
     /// Gets the precedence of this operator
     pub fn precedence(&self) -> ExprPrecedence {
         use AssocOp::*;
         match *self {
             As => ExprPrecedence::Cast,
-            Multiply | Divide | Modulus => ExprPrecedence::Product,
-            Add | Subtract => ExprPrecedence::Sum,
-            ShiftLeft | ShiftRight => ExprPrecedence::Shift,
-            BitAnd => ExprPrecedence::BitAnd,
-            BitXor => ExprPrecedence::BitXor,
-            BitOr => ExprPrecedence::BitOr,
-            Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual => ExprPrecedence::Compare,
-            LAnd => ExprPrecedence::LAnd,
-            LOr => ExprPrecedence::LOr,
+            Binary(bin_op) => bin_op.precedence(),
             DotDot | DotDotEq => ExprPrecedence::Range,
             Assign | AssignOp(_) => ExprPrecedence::Assign,
         }
@@ -161,22 +92,17 @@ impl AssocOp {
         // NOTE: it is a bug to have an operators that has same precedence but different fixities!
         match *self {
             Assign | AssignOp(_) => Fixity::Right,
-            As | Multiply | Divide | Modulus | Add | Subtract | ShiftLeft | ShiftRight | BitAnd
-            | BitXor | BitOr | LAnd | LOr => Fixity::Left,
-            Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual | DotDot | DotDotEq => {
-                Fixity::None
-            }
+            Binary(binop) => binop.fixity(),
+            As => Fixity::Left,
+            DotDot | DotDotEq => Fixity::None,
         }
     }
 
     pub fn is_comparison(&self) -> bool {
         use AssocOp::*;
         match *self {
-            Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual => true,
-            Assign | AssignOp(_) | As | Multiply | Divide | Modulus | Add | Subtract
-            | ShiftLeft | ShiftRight | BitAnd | BitXor | BitOr | LAnd | LOr | DotDot | DotDotEq => {
-                false
-            }
+            Binary(binop) => binop.is_comparison(),
+            Assign | AssignOp(_) | As | DotDot | DotDotEq => false,
         }
     }
 
@@ -184,34 +110,7 @@ impl AssocOp {
         use AssocOp::*;
         match *self {
             Assign | AssignOp(_) => true,
-            Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual | As | Multiply
-            | Divide | Modulus | Add | Subtract | ShiftLeft | ShiftRight | BitAnd | BitXor
-            | BitOr | LAnd | LOr | DotDot | DotDotEq => false,
-        }
-    }
-
-    pub fn to_ast_binop(&self) -> Option<BinOpKind> {
-        use AssocOp::*;
-        match *self {
-            Less => Some(BinOpKind::Lt),
-            Greater => Some(BinOpKind::Gt),
-            LessEqual => Some(BinOpKind::Le),
-            GreaterEqual => Some(BinOpKind::Ge),
-            Equal => Some(BinOpKind::Eq),
-            NotEqual => Some(BinOpKind::Ne),
-            Multiply => Some(BinOpKind::Mul),
-            Divide => Some(BinOpKind::Div),
-            Modulus => Some(BinOpKind::Rem),
-            Add => Some(BinOpKind::Add),
-            Subtract => Some(BinOpKind::Sub),
-            ShiftLeft => Some(BinOpKind::Shl),
-            ShiftRight => Some(BinOpKind::Shr),
-            BitAnd => Some(BinOpKind::BitAnd),
-            BitXor => Some(BinOpKind::BitXor),
-            BitOr => Some(BinOpKind::BitOr),
-            LAnd => Some(BinOpKind::And),
-            LOr => Some(BinOpKind::Or),
-            Assign | AssignOp(_) | As | DotDot | DotDotEq => None,
+            As | Binary(_) | DotDot | DotDotEq => false,
         }
     }
 
@@ -221,16 +120,19 @@ impl AssocOp {
     /// parentheses while having a high degree of confidence on the correctness of the suggestion.
     pub fn can_continue_expr_unambiguously(&self) -> bool {
         use AssocOp::*;
+        use BinOpKind::*;
         matches!(
             self,
-            BitXor | // `{ 42 } ^ 3`
             Assign | // `{ 42 } = { 42 }`
-            Divide | // `{ 42 } / 42`
-            Modulus | // `{ 42 } % 2`
-            ShiftRight | // `{ 42 } >> 2`
-            LessEqual | // `{ 42 } <= 3`
-            Greater | // `{ 42 } > 3`
-            GreaterEqual | // `{ 42 } >= 3`
+            Binary(
+                BitXor | // `{ 42 } ^ 3`
+                Div | // `{ 42 } / 42`
+                Rem | // `{ 42 } % 2`
+                Shr | // `{ 42 } >> 2`
+                Le | // `{ 42 } <= 3`
+                Gt | // `{ 42 } > 3`
+                Ge   // `{ 42 } >= 3`
+            ) |
             AssignOp(_) | // `{ 42 } +=`
             // Equal | // `{ 42 } == { 42 }`    Accepting these here would regress incorrect
             // NotEqual | // `{ 42 } != { 42 }  struct literals parser recovery.