Add two new whitespace options (#1109)

* An option to leave a space before the colon in a type annotation

* An option to leave a space before the colon in a trait or lifetime bound

src/config.rs

@@ -408,6 +408,9 @@ create_config! {
     match_wildcard_trailing_comma: bool, true, "Put a trailing comma after a wildcard arm";
     closure_block_indent_threshold: isize, 5, "How many lines a closure must have before it is \
                                                block indented. -1 means never use block indent.";
+    space_before_type_annotation: bool, false,
+        "Leave a space before the colon in a type annotation";
+    space_before_bound: bool, false, "Leave a space before the colon in a trait or lifetime bound";
     use_try_shorthand: bool, false, "Replace uses of the try! macro by the ? shorthand";
     write_mode: WriteMode, WriteMode::Replace,
         "What Write Mode to use when none is supplied: Replace, Overwrite, Display, Diff, Coverage";

src/items.rs

@@ -45,13 +45,17 @@ impl Rewrite for ast::Local {
             let mut infix = String::new();
 
             if let Some(ref ty) = self.ty {
-                // 2 = ": ".len()
+                let separator = if context.config.space_before_type_annotation {
+                    " : "
+                } else {
+                    ": "
+                };
+                let indent = offset + last_line_width(&result) + separator.len();
                 // 1 = ;
-                let indent = offset + last_line_width(&result) + 2;
                 let budget = try_opt!(width.checked_sub(indent.width() + 1));
                 let rewrite = try_opt!(ty.rewrite(context, budget, indent));
 
-                infix.push_str(": ");
+                infix.push_str(separator);
                 infix.push_str(&rewrite);
             }
 
@@ -998,6 +1002,14 @@ pub fn rewrite_type_alias(context: &RewriteContext,
     Some(result)
 }
 
+fn type_annotation_spacing(config: &Config) -> &str {
+    if config.space_before_type_annotation {
+        " "
+    } else {
+        ""
+    }
+}
+
 impl Rewrite for ast::StructField {
     fn rewrite(&self, context: &RewriteContext, width: usize, offset: Indent) -> Option<String> {
         if contains_skip(&self.attrs) {
@@ -1014,8 +1026,9 @@ impl Rewrite for ast::StructField {
             attr_str.push_str(&offset.to_string(context.config));
         }
 
+        let type_annotation_spacing = type_annotation_spacing(context.config);
         let result = match name {
-            Some(name) => format!("{}{}{}: ", attr_str, vis, name),
+            Some(name) => format!("{}{}{}{}: ", attr_str, vis, name, type_annotation_spacing),
             None => format!("{}{}", attr_str, vis),
         };
 
@@ -1034,11 +1047,13 @@ pub fn rewrite_static(prefix: &str,
                       expr_opt: Option<&ptr::P<ast::Expr>>,
                       context: &RewriteContext)
                       -> Option<String> {
-    let prefix = format!("{}{} {}{}: ",
+    let type_annotation_spacing = type_annotation_spacing(context.config);
+    let prefix = format!("{}{} {}{}{}: ",
                          format_visibility(vis),
                          prefix,
                          format_mutability(mutability),
-                         ident);
+                         ident,
+                         type_annotation_spacing);
     // 2 = " =".len()
     let ty_str = try_opt!(ty.rewrite(context,
                                      context.config.max_width - context.block_indent.width() -
@@ -1117,6 +1132,9 @@ impl Rewrite for ast::Arg {
             let mut result = try_opt!(self.pat.rewrite(context, width, offset));
 
             if self.ty.node != ast::TyKind::Infer {
+                if context.config.space_before_type_annotation {
+                    result.push_str(" ");
+                }
                 result.push_str(": ");
                 let max_width = try_opt!(width.checked_sub(result.len()));
                 let ty_str = try_opt!(self.ty.rewrite(context, max_width, offset + result.len()));

src/types.rs

@@ -406,7 +406,12 @@ fn rewrite_bounded_lifetime<'b, I>(lt: &ast::Lifetime,
         let appendix: Vec<_> = try_opt!(bounds.into_iter()
             .map(|b| b.rewrite(context, width, offset))
             .collect());
-        let result = format!("{}: {}", result, appendix.join(" + "));
+        let bound_spacing = if context.config.space_before_bound {
+            " "
+        } else {
+            ""
+        };
+        let result = format!("{}{}: {}", result, bound_spacing, appendix.join(" + "));
         wrap_str(result, context.config.max_width, width, offset)
     }
 }
@@ -449,6 +454,9 @@ impl Rewrite for ast::TyParam {
         let mut result = String::with_capacity(128);
         result.push_str(&self.ident.to_string());
         if !self.bounds.is_empty() {
+            if context.config.space_before_bound {
+                result.push_str(" ");
+            }
             result.push_str(": ");
 
             let bounds: String = try_opt!(self.bounds

tests/source/space-before-bound.rs

@@ -0,0 +1,4 @@
+// rustfmt-space_before_bound: true
+
+trait Trait {}
+fn f<'a, 'b: 'a, T: Trait>() {}

tests/source/space-before-type-annotation.rs

@@ -0,0 +1,10 @@
+// rustfmt-space_before_type_annotation: true
+
+static staticVar: i32 = 42;
+const constVar: i32 = 42;
+fn foo(paramVar: i32) {
+    let localVar: i32 = 42;
+}
+struct S {
+    fieldVar: i32,
+}

tests/target/space-before-bound.rs

@@ -0,0 +1,4 @@
+// rustfmt-space_before_bound: true
+
+trait Trait {}
+fn f<'a, 'b : 'a, T : Trait>() {}

tests/target/space-before-type-annotation.rs

@@ -0,0 +1,10 @@
+// rustfmt-space_before_type_annotation: true
+
+static staticVar : i32 = 42;
+const constVar : i32 = 42;
+fn foo(paramVar : i32) {
+    let localVar : i32 = 42;
+}
+struct S {
+    fieldVar : i32,
+}