normalize match reference style, #929

Configurations.md

@@ -1885,6 +1885,52 @@ fn main() {
 
 See also: [`match_block_trailing_comma`](#match_block_trailing_comma).
 
+## `match_reference_style`
+
+Normalize match reference style
+
+- **Default value**: `manual`
+- **Possible values**: `manual`, `reference`, `dereference`, `auto`
+- **Stable**: No
+
+**Note:** `auto` style requires Rust v1.26.0 or later
+
+#### `manual`
+
+don't touch anything
+
+#### `reference`
+
+```rust
+fn hello(name: &Option<&str>) {
+    match name {
+        &Some(name) => println!("Hello {}!", name),
+        &None => println!("I don't know who you are."),
+    }
+}
+```
+
+#### `dereference`
+
+```rust
+fn hello(name: &Option<&str>) {
+    match *name {
+        Some(name) => println!("Hello {}!", name),
+        None => println!("I don't know who you are."),
+    }
+}
+```
+
+#### `auto`
+
+```rust
+fn hello(name: &Option<&str>) {
+    match name {
+        Some(name) => println!("Hello {}!", name),
+        None => println!("I don't know who you are."),
+    }
+}
+```
 
 ## `blank_lines_upper_bound`
 

src/config/mod.rs

@@ -88,6 +88,8 @@ create_config! {
                                              threshold.";
     match_arm_blocks: bool, true, false, "Wrap the body of arms in blocks when it does not fit on \
         the same line with the pattern of arms";
+    match_reference_style: MatchReferenceStyle, MatchReferenceStyle::Manual, false,
+        "Normalize match reference style";
     force_multiline_blocks: bool, false, false,
         "Force multiline closure bodies and match arms to be wrapped in a block";
     fn_args_density: Density, Density::Tall, false, "Argument density in functions";

src/config/options.rs

@@ -135,6 +135,25 @@ configuration_option_enum! { IndentStyle:
     Block,
 }
 
+configuration_option_enum! { MatchReferenceStyle:
+    Manual,
+    // match x {
+    //    &A => ...,
+    //    ...
+    // }
+    Reference,
+    // match *x {
+    //     A => ...,
+    //     ...
+    // }
+    Dereference,
+    // match x {
+    //     A => ...,
+    //     ...
+    // }
+    Auto
+}
+
 configuration_option_enum! { Density:
     // Fit as much on one line as possible.
     Compressed,

src/matches.rs

@@ -18,7 +18,7 @@ use syntax::{ast, ptr};
 
 use codemap::SpanUtils;
 use comment::combine_strs_with_missing_comments;
-use config::{Config, ControlBraceStyle, IndentStyle};
+use config::{Config, ControlBraceStyle, IndentStyle, MatchReferenceStyle};
 use expr::{
     format_expr, is_empty_block, is_simple_block, is_unsafe_block, prefer_next_line,
     rewrite_multiple_patterns, ExprType, RhsTactics, ToExpr,
@@ -91,7 +91,7 @@ pub fn rewrite_match(
         IndentStyle::Visual => cond_shape.shrink_left(6)?,
         IndentStyle::Block => cond_shape.offset_left(6)?,
     };
-    let cond_str = cond.rewrite(context, cond_shape)?;
+    let mut cond_str = cond.rewrite(context, cond_shape)?;
     let alt_block_sep = &shape.indent.to_string_with_newline(context.config);
     let block_sep = match context.config.control_brace_style() {
         ControlBraceStyle::AlwaysNextLine => alt_block_sep,
@@ -138,13 +138,28 @@ pub fn rewrite_match(
         }
     } else {
         let span_after_cond = mk_sp(cond.span.hi(), span.hi());
+        let mut arms_str =
+            rewrite_match_arms(context, arms, shape, span_after_cond, open_brace_pos)?;
+
+        rewrite_match_reference_style(
+            context,
+            cond,
+            arms,
+            shape,
+            cond_shape,
+            span_after_cond,
+            open_brace_pos,
+            &mut cond_str,
+            &mut arms_str,
+        )?;
+
         Some(format!(
             "match {}{}{{\n{}{}{}\n{}}}",
             cond_str,
             block_sep,
             inner_attrs_str,
             nested_indent_str,
-            rewrite_match_arms(context, arms, shape, span_after_cond, open_brace_pos)?,
+            arms_str,
             shape.indent.to_string(context.config),
         ))
     }
@@ -183,6 +198,109 @@ fn collect_beginning_verts(
     beginning_verts
 }
 
+fn rewrite_match_reference_style(
+    context: &RewriteContext,
+    cond: &ast::Expr,
+    arms: &[ast::Arm],
+    shape: Shape,
+    cond_shape: Shape,
+    span_after_cond: Span,
+    open_brace_pos: BytePos,
+    cond_str: &mut String,
+    arms_str: &mut String,
+) -> Option<()> {
+    let match_in_reference_style = arms.iter().all(|arm| {
+        arm.pats.iter().all(|pat| match pat.node {
+            ast::PatKind::Wild | ast::PatKind::Ref(..) => true,
+            _ => false,
+        })
+    });
+    let match_in_derefrence_style = match cond.node {
+        ast::ExprKind::Unary(ast::UnOp::Deref, _) => true,
+        _ => false,
+    };
+
+    let prepend_arms_ref = || {
+        arms.iter()
+            .map(|arm| {
+                let pats = arm
+                    .pats
+                    .iter()
+                    .map(|pat| {
+                        ptr::P(ast::Pat {
+                            id: pat.id,
+                            node: ast::PatKind::Ref(pat.clone(), ast::Mutability::Immutable),
+                            span: pat.span,
+                        })
+                    })
+                    .collect::<Vec<_>>();
+
+                ast::Arm {
+                    pats,
+                    ..arm.clone()
+                }
+            })
+            .collect::<Vec<_>>()
+    };
+
+    let strip_arms_ref = || {
+        arms.iter()
+            .map(|arm| {
+                let pats = arm
+                    .pats
+                    .iter()
+                    .map(|pat| match pat.node {
+                        ast::PatKind::Ref(ref pat, _) => pat,
+                        _ => pat,
+                    })
+                    .cloned()
+                    .collect::<Vec<_>>();
+
+                ast::Arm {
+                    pats,
+                    ..arm.clone()
+                }
+            })
+            .collect::<Vec<_>>()
+    };
+
+    match context.config.match_reference_style() {
+        MatchReferenceStyle::Reference if match_in_derefrence_style => {
+            if let ast::ExprKind::Unary(ast::UnOp::Deref, ref cond) = cond.node {
+                *cond_str = cond.rewrite(context, cond_shape)?;
+            }
+
+            let arms = prepend_arms_ref();
+
+            *arms_str = rewrite_match_arms(context, &arms, shape, span_after_cond, open_brace_pos)?
+        }
+        MatchReferenceStyle::Dereference if match_in_reference_style => {
+            let cond = ast::Expr {
+                node: ast::ExprKind::Unary(ast::UnOp::Deref, ptr::P(cond.clone())),
+                ..cond.clone()
+            };
+            *cond_str = cond.rewrite(context, cond_shape)?;
+
+            let arms = strip_arms_ref();
+
+            *arms_str = rewrite_match_arms(context, &arms, shape, span_after_cond, open_brace_pos)?
+        }
+        MatchReferenceStyle::Auto if match_in_derefrence_style => {
+            if let ast::ExprKind::Unary(ast::UnOp::Deref, ref cond) = cond.node {
+                *cond_str = cond.rewrite(context, cond_shape)?;
+            }
+        }
+        MatchReferenceStyle::Auto if match_in_reference_style => {
+            let arms = strip_arms_ref();
+
+            *arms_str = rewrite_match_arms(context, &arms, shape, span_after_cond, open_brace_pos)?
+        }
+        _ => {}
+    }
+
+    Some(())
+}
+
 fn rewrite_match_arms(
     context: &RewriteContext,
     arms: &[ast::Arm],

tests/source/configs/match_reference_style/auto.rs

@@ -0,0 +1,23 @@
+// rustfmt-match_reference_style: auto
+// Normalize match reference style
+
+fn hello(name: &Option<&str>) {
+    match name {
+        &Some(name) => println!("Hello {}!", name),
+        &None => println!("I don't know who you are."),
+    }
+}
+
+fn kiss(name: &Option<&str>) {
+    match *name {
+        Some(name) => println!("Kiss {}!", name),
+        None => println!("I don't know who you are."),
+    }
+}
+
+fn main() {
+    let name = Some("rustfmt");
+
+    hello(&name);
+    kiss(&name);
+}

tests/source/configs/match_reference_style/derefence.rs

@@ -0,0 +1,23 @@
+// rustfmt-match_reference_style: dereference
+// Normalize match reference style
+
+fn hello(name: &Option<&str>) {
+    match name {
+        &Some(name) => println!("Hello {}!", name),
+        &None => println!("I don't know who you are."),
+    }
+}
+
+fn kiss(name: &Option<&str>) {
+    match *name {
+        Some(name) => println!("Kiss {}!", name),
+        None => println!("I don't know who you are."),
+    }
+}
+
+fn main() {
+    let name = Some("rustfmt");
+
+    hello(&name);
+    kiss(&name);
+}

tests/source/configs/match_reference_style/reference.rs

@@ -0,0 +1,23 @@
+// rustfmt-match_reference_style: reference
+// Normalize match reference style
+
+fn hello(name: &Option<&str>) {
+    match name {
+        &Some(name) => println!("Hello {}!", name),
+        &None => println!("I don't know who you are."),
+    }
+}
+
+fn kiss(name: &Option<&str>) {
+    match *name {
+        Some(name) => println!("Kiss {}!", name),
+        None => println!("I don't know who you are."),
+    }
+}
+
+fn main() {
+    let name = Some("rustfmt");
+
+    hello(&name);
+    kiss(&name);
+}

tests/target/configs/match_reference_style/auto.rs

@@ -0,0 +1,23 @@
+// rustfmt-match_reference_style: auto
+// Normalize match reference style
+
+fn hello(name: &Option<&str>) {
+    match name {
+        Some(name) => println!("Hello {}!", name),
+        None => println!("I don't know who you are."),
+    }
+}
+
+fn kiss(name: &Option<&str>) {
+    match name {
+        Some(name) => println!("Kiss {}!", name),
+        None => println!("I don't know who you are."),
+    }
+}
+
+fn main() {
+    let name = Some("rustfmt");
+
+    hello(&name);
+    kiss(&name);
+}

tests/target/configs/match_reference_style/derefence.rs

@@ -0,0 +1,23 @@
+// rustfmt-match_reference_style: dereference
+// Normalize match reference style
+
+fn hello(name: &Option<&str>) {
+    match *name {
+        Some(name) => println!("Hello {}!", name),
+        None => println!("I don't know who you are."),
+    }
+}
+
+fn kiss(name: &Option<&str>) {
+    match *name {
+        Some(name) => println!("Kiss {}!", name),
+        None => println!("I don't know who you are."),
+    }
+}
+
+fn main() {
+    let name = Some("rustfmt");
+
+    hello(&name);
+    kiss(&name);
+}

tests/target/configs/match_reference_style/reference.rs

@@ -0,0 +1,23 @@
+// rustfmt-match_reference_style: reference
+// Normalize match reference style
+
+fn hello(name: &Option<&str>) {
+    match name {
+        &Some(name) => println!("Hello {}!", name),
+        &None => println!("I don't know who you are."),
+    }
+}
+
+fn kiss(name: &Option<&str>) {
+    match name {
+        &Some(name) => println!("Kiss {}!", name),
+        &None => println!("I don't know who you are."),
+    }
+}
+
+fn main() {
+    let name = Some("rustfmt");
+
+    hello(&name);
+    kiss(&name);
+}