Add attr_fn_like_width to the width heuristics

It is a bit larger than than `fn_call_width` which we used previously, so fewer attributes get reformatted.

Closes rust-lang#2929

Author: Nick Cameron

src/attr.rs

@@ -224,7 +224,7 @@ impl Rewrite for ast::MetaItem {
                     // 1 = "]"
                     shape.sub_width(1)?,
                     self.span,
-                    context.config.width_heuristics().fn_call_width,
+                    context.config.width_heuristics().attr_fn_like_width,
                     Some(if has_trailing_comma {
                         SeparatorTactic::Always
                     } else {

src/config/options.rs

@@ -316,6 +316,9 @@ pub struct WidthHeuristics {
     // Maximum width of the args of a function call before falling back
     // to vertical formatting.
     pub fn_call_width: usize,
+    // Maximum width of the args of a function-like attributes before falling
+    // back to vertical formatting.
+    pub attr_fn_like_width: usize,
     // Maximum width in the body of a struct lit before falling back to
     // vertical formatting.
     pub struct_lit_width: usize,
@@ -337,6 +340,7 @@ impl WidthHeuristics {
     pub fn null() -> WidthHeuristics {
         WidthHeuristics {
             fn_call_width: usize::max_value(),
+            attr_fn_like_width: usize::max_value(),
             struct_lit_width: 0,
             struct_variant_width: 0,
             array_width: usize::max_value(),
@@ -348,6 +352,7 @@ impl WidthHeuristics {
     pub fn set(max_width: usize) -> WidthHeuristics {
         WidthHeuristics {
             fn_call_width: max_width,
+            attr_fn_like_width: max_width,
             struct_lit_width: max_width,
             struct_variant_width: max_width,
             array_width: max_width,
@@ -368,6 +373,7 @@ impl WidthHeuristics {
         };
         WidthHeuristics {
             fn_call_width: (60.0 * max_width_ratio).round() as usize,
+            attr_fn_like_width: (70.0 * max_width_ratio).round() as usize,
             struct_lit_width: (18.0 * max_width_ratio).round() as usize,
             struct_variant_width: (35.0 * max_width_ratio).round() as usize,
             array_width: (60.0 * max_width_ratio).round() as usize,

tests/source/enum.rs

@@ -189,7 +189,7 @@ pub enum QlError {
     // (from, to)
     #[fail(display = "Translation error: from {} to {}", 0, 1)] TranslationError(String, String),
     // (kind, input, expected)
-    #[fail(display = "Could not find {}: Found: {}, expected: {:?}", 0, 1, 2)] ResolveError(&'static str, String, Option<String>),
+    #[fail(display = "aaaaaaaaaaaaCould not find {}: Found: {}, expected: {:?}", 0, 1, 2)] ResolveError(&'static str, String, Option<String>),
 }
 
 // #2594

tests/target/enum.rs

@@ -255,7 +255,7 @@ pub enum QlError {
     TranslationError(String, String),
     // (kind, input, expected)
     #[fail(
-        display = "Could not find {}: Found: {}, expected: {:?}",
+        display = "aaaaaaaaaaaaCould not find {}: Found: {}, expected: {:?}",
         0, 1, 2
     )]
     ResolveError(&'static str, String, Option<String>),