Add a module to pretty-print suggestions

clippy_lints/src/lib.rs

@@ -3,6 +3,7 @@
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(custom_attribute)]
+#![feature(dotdot_in_tuple_patterns)]
 #![feature(iter_arith)]
 #![feature(question_mark)]
 #![feature(rustc_private)]

clippy_lints/src/utils/higher.rs

@@ -0,0 +1,28 @@
+//! This module contains functions for retrieve the original AST from lowered `hir`.
+
+use rustc::hir;
+use syntax::ast;
+
+/// Convert a hir binary operator to the corresponding `ast` type.
+pub fn binop(op: hir::BinOp_) -> ast::BinOpKind {
+    match op {
+        hir::BiEq => ast::BinOpKind::Eq,
+        hir::BiGe => ast::BinOpKind::Ge,
+        hir::BiGt => ast::BinOpKind::Gt,
+        hir::BiLe => ast::BinOpKind::Le,
+        hir::BiLt => ast::BinOpKind::Lt,
+        hir::BiNe => ast::BinOpKind::Ne,
+        hir::BiOr => ast::BinOpKind::Or,
+        hir::BiAdd => ast::BinOpKind::Add,
+        hir::BiAnd => ast::BinOpKind::And,
+        hir::BiBitAnd => ast::BinOpKind::BitAnd,
+        hir::BiBitOr => ast::BinOpKind::BitOr,
+        hir::BiBitXor => ast::BinOpKind::BitXor,
+        hir::BiDiv => ast::BinOpKind::Div,
+        hir::BiMul => ast::BinOpKind::Mul,
+        hir::BiRem => ast::BinOpKind::Rem,
+        hir::BiShl => ast::BinOpKind::Shl,
+        hir::BiShr => ast::BinOpKind::Shr,
+        hir::BiSub => ast::BinOpKind::Sub,
+    }
+}

clippy_lints/src/utils/mod.rs

@@ -18,12 +18,14 @@ use syntax::codemap::{ExpnInfo, Span, ExpnFormat};
 use syntax::errors::DiagnosticBuilder;
 use syntax::ptr::P;
 
+pub mod cargo;
 pub mod comparisons;
 pub mod conf;
+pub mod higher;
 mod hir;
 pub mod paths;
+pub mod sugg;
 pub use self::hir::{SpanlessEq, SpanlessHash};
-pub mod cargo;
 
 pub type MethodArgs = HirVec<P<Expr>>;
 

clippy_lints/src/utils/sugg.rs

@@ -0,0 +1,258 @@
+use rustc::hir;
+use rustc::lint::{EarlyContext, LateContext};
+use std::borrow::Cow;
+use std;
+use syntax::ast;
+use syntax::util::parser::AssocOp;
+use utils::{higher, snippet};
+
+/// A helper type to build suggestion correctly handling parenthesis.
+pub enum Sugg<'a> {
+    /// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
+    NonParen(Cow<'a, str>),
+    /// An expression that does not fit in other variants.
+    MaybeParen(Cow<'a, str>),
+    /// A binary operator expression, including `as`-casts and explicit type coercion.
+    BinOp(AssocOp, Cow<'a, str>),
+}
+
+impl<'a> std::fmt::Display for Sugg<'a> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+        match *self {
+            Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) | Sugg::BinOp(_, ref s) => {
+                s.fmt(f)
+            }
+        }
+    }
+}
+
+impl<'a> Sugg<'a> {
+    pub fn hir(cx: &LateContext, expr: &'a hir::Expr, default: &'a str) -> Sugg<'a> {
+        let snippet = snippet(cx, expr.span, default);
+
+        match expr.node {
+            hir::ExprAddrOf(..) |
+            hir::ExprBox(..) |
+            hir::ExprClosure(..) |
+            hir::ExprIf(..) |
+            hir::ExprUnary(..) |
+            hir::ExprMatch(..) => Sugg::MaybeParen(snippet),
+            hir::ExprAgain(..) |
+            hir::ExprBlock(..) |
+            hir::ExprBreak(..) |
+            hir::ExprCall(..) |
+            hir::ExprField(..) |
+            hir::ExprIndex(..) |
+            hir::ExprInlineAsm(..) |
+            hir::ExprLit(..) |
+            hir::ExprLoop(..) |
+            hir::ExprMethodCall(..) |
+            hir::ExprPath(..) |
+            hir::ExprRepeat(..) |
+            hir::ExprRet(..) |
+            hir::ExprStruct(..) |
+            hir::ExprTup(..) |
+            hir::ExprTupField(..) |
+            hir::ExprVec(..) |
+            hir::ExprWhile(..) => Sugg::NonParen(snippet),
+            hir::ExprAssign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
+            hir::ExprAssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
+            hir::ExprBinary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
+            hir::ExprCast(..) => Sugg::BinOp(AssocOp::As, snippet),
+            hir::ExprType(..) => Sugg::BinOp(AssocOp::Colon, snippet),
+        }
+    }
+
+    pub fn ast(cx: &EarlyContext, expr: &'a ast::Expr, default: &'a str) -> Sugg<'a> {
+        use syntax::ast::RangeLimits;
+
+        let snippet = snippet(cx, expr.span, default);
+
+        match expr.node {
+            ast::ExprKind::AddrOf(..) |
+            ast::ExprKind::Box(..) |
+            ast::ExprKind::Closure(..) |
+            ast::ExprKind::If(..) |
+            ast::ExprKind::IfLet(..) |
+            ast::ExprKind::InPlace(..) |
+            ast::ExprKind::Unary(..) |
+            ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
+            ast::ExprKind::Again(..) |
+            ast::ExprKind::Block(..) |
+            ast::ExprKind::Break(..) |
+            ast::ExprKind::Call(..) |
+            ast::ExprKind::Field(..) |
+            ast::ExprKind::ForLoop(..) |
+            ast::ExprKind::Index(..) |
+            ast::ExprKind::InlineAsm(..) |
+            ast::ExprKind::Lit(..) |
+            ast::ExprKind::Loop(..) |
+            ast::ExprKind::Mac(..) |
+            ast::ExprKind::MethodCall(..) |
+            ast::ExprKind::Paren(..) |
+            ast::ExprKind::Path(..) |
+            ast::ExprKind::Repeat(..) |
+            ast::ExprKind::Ret(..) |
+            ast::ExprKind::Struct(..) |
+            ast::ExprKind::Try(..) |
+            ast::ExprKind::Tup(..) |
+            ast::ExprKind::TupField(..) |
+            ast::ExprKind::Vec(..) |
+            ast::ExprKind::While(..) |
+            ast::ExprKind::WhileLet(..) => Sugg::NonParen(snippet),
+            ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
+            ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotDot, snippet),
+            ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
+            ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
+            ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
+            ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
+            ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
+        }
+    }
+
+    /// Convenience method to create the `lhs && rhs` suggestion.
+    pub fn and(&self, rhs: &Self) -> Sugg<'static> {
+        make_binop(ast::BinOpKind::And, self, rhs)
+    }
+}
+
+impl<'a, 'b> std::ops::Sub<&'b Sugg<'b>> for &'a Sugg<'a> {
+    type Output = Sugg<'static>;
+    fn sub(self, rhs: &'b Sugg<'b>) -> Sugg<'static> {
+        make_binop(ast::BinOpKind::Sub, self, rhs)
+    }
+}
+
+struct ParenHelper<T> {
+    paren: bool,
+    wrapped: T,
+}
+
+impl<T> ParenHelper<T> {
+    fn new(paren: bool, wrapped: T) -> Self {
+        ParenHelper {
+            paren: paren,
+            wrapped: wrapped,
+        }
+    }
+}
+
+impl<T: std::fmt::Display> std::fmt::Display for ParenHelper<T> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+        if self.paren {
+            write!(f, "({})", self.wrapped)
+        } else {
+            self.wrapped.fmt(f)
+        }
+    }
+}
+
+/// Build the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
+///
+/// Precedence of shift operator relative to other arithmetic operation is often confusing so
+/// parenthesis will always be added for a mix of these.
+pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg, rhs: &Sugg) -> Sugg<'static> {
+    fn is_shift(op: &AssocOp) -> bool {
+        matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
+    }
+
+    fn is_arith(op: &AssocOp) -> bool {
+        matches!(*op, AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus)
+    }
+
+    fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
+        other.precedence() < op.precedence() ||
+            (other.precedence() == op.precedence() &&
+                ((op != other && associativity(op) != dir) ||
+                 (op == other && associativity(op) != Associativity::Both))) ||
+             is_shift(op) && is_arith(other) ||
+             is_shift(other) && is_arith(op)
+    }
+
+    let aop = AssocOp::from_ast_binop(op);
+
+    let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
+        needs_paren(&aop, lop, Associativity::Left)
+    } else {
+        false
+    };
+
+    let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
+        needs_paren(&aop, rop, Associativity::Right)
+    } else {
+        false
+    };
+
+    Sugg::BinOp(aop,
+                format!("{} {} {}",
+                        ParenHelper::new(lhs_paren, lhs),
+                        op.to_string(),
+                        ParenHelper::new(rhs_paren, rhs)).into())
+}
+
+#[derive(PartialEq, Eq)]
+enum Associativity {
+    Both,
+    Left,
+    None,
+    Right,
+}
+
+/// Return the associativity/fixity of an operator. The difference with `AssocOp::fixity` is that
+/// an operator can be both left and right associative (such as `+`:
+/// `a + b + c == (a + b) + c == a + (b + c)`.
+///
+/// Chained `as` and explicit `:` type coercion never need inner parenthesis so they are considered
+/// associative.
+fn associativity(op: &AssocOp) -> Associativity {
+    use syntax::util::parser::AssocOp::*;
+
+    match *op {
+        Inplace | Assign | AssignOp(_) => Associativity::Right,
+        Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply |
+        As | Colon => Associativity::Both,
+    Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft |
+        ShiftRight | Subtract => Associativity::Left,
+        DotDot | DotDotDot => Associativity::None
+    }
+}
+
+/// Convert a `hir::BinOp` to the corresponding assigning binary operator.
+fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
+    use rustc::hir::BinOp_::*;
+    use syntax::parse::token::BinOpToken::*;
+
+    AssocOp::AssignOp(match op.node {
+        BiAdd => Plus,
+        BiBitAnd => And,
+        BiBitOr => Or,
+        BiBitXor => Caret,
+        BiDiv => Slash,
+        BiMul => Star,
+        BiRem => Percent,
+        BiShl => Shl,
+        BiShr => Shr,
+        BiSub => Minus,
+        BiAnd | BiEq | BiGe | BiGt | BiLe | BiLt | BiNe | BiOr => panic!("This operator does not exist"),
+    })
+}
+
+/// Convert an `ast::BinOp` to the corresponding assigning binary operator.
+fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
+    use syntax::ast::BinOpKind::*;
+    use syntax::parse::token::BinOpToken;
+
+    AssocOp::AssignOp(match op.node {
+        Add => BinOpToken::Plus,
+        BitAnd => BinOpToken::And,
+        BitOr => BinOpToken::Or,
+        BitXor => BinOpToken::Caret,
+        Div => BinOpToken::Slash,
+        Mul => BinOpToken::Star,
+        Rem => BinOpToken::Percent,
+        Shl => BinOpToken::Shl,
+        Shr => BinOpToken::Shr,
+        Sub => BinOpToken::Minus,
+        And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
+    })
+}