diff --git a/CHANGELOG.md b/CHANGELOG.md
index 836b2fd81a1..be4e6c42074 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,9 +2,12 @@
 
 ## [Unreleased]
 
+### Changed
+
 - Change option `format_doc_comment` to `format_code_in_doc_comment`.
 - `use_small_heuristics` changed to be an enum and stabilised. Configuration
   options are now ready for 1.0.
+- Stabilise `fn_args_density` configuration option and rename it to `fn_args_layout` #3581
 
 ## [1.2.2] 2019-04-24
 
diff --git a/Configurations.md b/Configurations.md
index 3737b1c9a4e..304bc690034 100644
--- a/Configurations.md
+++ b/Configurations.md
@@ -629,13 +629,13 @@ trailing whitespaces.
 - **Possible values**: `true`, `false`
 - **Stable**: No (tracking issue: #3392)
 
-## `fn_args_density`
+## `fn_args_layout`
 
-Argument density in functions
+Control the layout of arguments in a function
 
 - **Default value**: `"Tall"`
 - **Possible values**: `"Compressed"`, `"Tall"`, `"Vertical"`
-- **Stable**: No (tracking issue: #3375)
+- **Stable**: Yes
 
 #### `"Tall"` (default):
 
diff --git a/Processes.md b/Processes.md
index 3f1c07c52b3..9d86d52b122 100644
--- a/Processes.md
+++ b/Processes.md
@@ -17,6 +17,7 @@ Open a pull request that closes the tracking issue. The tracking issue is listed
 
 - Update the `Config` enum marking the option as stable.
 - Update the the `Configuration.md` file marking the option as stable.
+- Update `CHANGELOG.md` marking the option as stable.
 
 ## After the stabilisation
 
diff --git a/src/config/mod.rs b/src/config/mod.rs
index eaa6d012d5b..1b9e97fc5bf 100644
--- a/src/config/mod.rs
+++ b/src/config/mod.rs
@@ -92,7 +92,8 @@ create_config! {
         the same line with the pattern of arms";
     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";
+    fn_args_layout: Density, Density::Tall, true,
+        "Control the layout of arguments in a function";
     brace_style: BraceStyle, BraceStyle::SameLineWhere, false, "Brace style for items";
     control_brace_style: ControlBraceStyle, ControlBraceStyle::AlwaysSameLine, false,
         "Brace style for control flow constructs";
@@ -501,7 +502,7 @@ struct_field_align_threshold = 0
 enum_discrim_align_threshold = 0
 match_arm_blocks = true
 force_multiline_blocks = false
-fn_args_density = "Tall"
+fn_args_layout = "Tall"
 brace_style = "SameLineWhere"
 control_brace_style = "AlwaysSameLine"
 trailing_semicolon = true
diff --git a/src/config/options.rs b/src/config/options.rs
index 72acaacd348..663c5d4dee2 100644
--- a/src/config/options.rs
+++ b/src/config/options.rs
@@ -58,10 +58,11 @@ pub enum IndentStyle {
 
 #[config_type]
 /// How to place a list-like items.
+/// FIXME: Issue-3581: this should be renamed to ItemsLayout when publishing 2.0
 pub enum Density {
     /// Fit as much on one line as possible.
     Compressed,
-    /// Use more lines.
+    /// Items are placed horizontally if sufficient space, vertically otherwise.
     Tall,
     /// Place every item on a separate line.
     Vertical,
diff --git a/src/items.rs b/src/items.rs
index 7640fa32d22..ea0475ccc57 100644
--- a/src/items.rs
+++ b/src/items.rs
@@ -15,7 +15,7 @@ use crate::comment::{
     FindUncommented,
 };
 use crate::config::lists::*;
-use crate::config::{BraceStyle, Config, Density, IndentStyle, Version};
+use crate::config::{BraceStyle, Config, IndentStyle, Version};
 use crate::expr::{
     format_expr, is_empty_block, is_simple_block_stmt, rewrite_assign_rhs, rewrite_assign_rhs_with,
     ExprType, RhsTactics,
@@ -703,7 +703,7 @@ pub(crate) fn format_impl(
             &generics.where_clause,
             context.config.brace_style(),
             Shape::legacy(where_budget, offset.block_only()),
-            Density::Vertical,
+            false,
             "{",
             where_span_end,
             self_ty.span.hi(),
@@ -1044,11 +1044,7 @@ pub(crate) fn format_trait(
 
         // Rewrite where-clause.
         if !generics.where_clause.predicates.is_empty() {
-            let where_density = if context.config.indent_style() == IndentStyle::Block {
-                Density::Compressed
-            } else {
-                Density::Tall
-            };
+            let where_on_new_line = context.config.indent_style() != IndentStyle::Block;
 
             let where_budget = context.budget(last_line_width(&result));
             let pos_before_where = if generic_bounds.is_empty() {
@@ -1062,7 +1058,7 @@ pub(crate) fn format_trait(
                 &generics.where_clause,
                 context.config.brace_style(),
                 Shape::legacy(where_budget, offset.block_only()),
-                where_density,
+                where_on_new_line,
                 "{",
                 None,
                 pos_before_where,
@@ -1171,7 +1167,7 @@ impl<'a> Rewrite for TraitAliasBounds<'a> {
             &self.generics.where_clause,
             context.config.brace_style(),
             shape,
-            Density::Compressed,
+            false,
             ";",
             None,
             self.generics.where_clause.span.lo(),
@@ -1423,7 +1419,7 @@ fn format_tuple_struct(
                 &generics.where_clause,
                 context.config.brace_style(),
                 Shape::legacy(where_budget, offset.block_only()),
-                Density::Compressed,
+                false,
                 ";",
                 None,
                 body_hi,
@@ -1499,7 +1495,7 @@ fn rewrite_type_prefix(
         &generics.where_clause,
         context.config.brace_style(),
         Shape::legacy(where_budget, indent),
-        Density::Vertical,
+        false,
         "=",
         None,
         generics.span.hi(),
@@ -2258,7 +2254,7 @@ fn rewrite_fn_base(
         where_clause,
         context.config.brace_style(),
         Shape::indented(indent, context.config),
-        Density::Tall,
+        true,
         "{",
         Some(span.hi()),
         pos_before_where,
@@ -2390,7 +2386,7 @@ fn rewrite_args(
         &arg_items,
         context
             .config
-            .fn_args_density()
+            .fn_args_layout()
             .to_list_tactic(arg_items.len()),
         Separator::Comma,
         one_line_budget,
@@ -2677,7 +2673,7 @@ fn rewrite_where_clause(
     where_clause: &ast::WhereClause,
     brace_style: BraceStyle,
     shape: Shape,
-    density: Density,
+    on_new_line: bool,
     terminator: &str,
     span_end: Option<BytePos>,
     span_end_before_where: BytePos,
@@ -2757,7 +2753,7 @@ fn rewrite_where_clause(
     } else {
         terminator.len()
     };
-    if density == Density::Tall
+    if on_new_line
         || preds_str.contains('\n')
         || shape.indent.width() + " where ".len() + preds_str.len() + end_length > shape.width
     {
@@ -2848,7 +2844,7 @@ fn format_generics(
             &generics.where_clause,
             brace_style,
             Shape::legacy(budget, offset.block_only()),
-            Density::Tall,
+            true,
             "{",
             Some(span.hi()),
             span_end_before_where,
diff --git a/src/lists.rs b/src/lists.rs
index f57a78f9874..428a0eab9b0 100644
--- a/src/lists.rs
+++ b/src/lists.rs
@@ -246,10 +246,7 @@ where
     let total_sep_len = sep.len() * sep_count.saturating_sub(1);
     let real_total = total_width + total_sep_len;
 
-    if real_total <= limit
-        && !pre_line_comments
-        && !items.into_iter().any(|item| item.as_ref().is_multiline())
-    {
+    if real_total <= limit && !items.into_iter().any(|item| item.as_ref().is_multiline()) {
         DefinitiveListTactic::Horizontal
     } else {
         match tactic {
diff --git a/tests/config/small_tabs.toml b/tests/config/small_tabs.toml
index d03ac281acb..35c8fd86467 100644
--- a/tests/config/small_tabs.toml
+++ b/tests/config/small_tabs.toml
@@ -3,7 +3,7 @@ comment_width = 80
 tab_spaces = 2
 newline_style = "Unix"
 brace_style = "SameLineWhere"
-fn_args_density = "Tall"
+fn_args_layout = "Tall"
 trailing_comma = "Vertical"
 indent_style = "Block"
 report_todo = "Always"
diff --git a/tests/source/configs/fn_args_density/compressed.rs b/tests/source/configs/fn_args_layout/compressed.rs
similarity index 92%
rename from tests/source/configs/fn_args_density/compressed.rs
rename to tests/source/configs/fn_args_layout/compressed.rs
index 86c0b42e53c..66a371c259f 100644
--- a/tests/source/configs/fn_args_density/compressed.rs
+++ b/tests/source/configs/fn_args_layout/compressed.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Compressed
+// rustfmt-fn_args_layout: Compressed
 // Function arguments density
 
 trait Lorem {
diff --git a/tests/source/configs/fn_args_density/tall.rs b/tests/source/configs/fn_args_layout/tall.rs
similarity index 93%
rename from tests/source/configs/fn_args_density/tall.rs
rename to tests/source/configs/fn_args_layout/tall.rs
index fc400e1c113..f11e86fd313 100644
--- a/tests/source/configs/fn_args_density/tall.rs
+++ b/tests/source/configs/fn_args_layout/tall.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Tall
+// rustfmt-fn_args_layout: Tall
 // Function arguments density
 
 trait Lorem {
diff --git a/tests/source/configs/fn_args_density/vertical.rs b/tests/source/configs/fn_args_layout/vertical.rs
similarity index 92%
rename from tests/source/configs/fn_args_density/vertical.rs
rename to tests/source/configs/fn_args_layout/vertical.rs
index 20b1427d83d..a23cc025225 100644
--- a/tests/source/configs/fn_args_density/vertical.rs
+++ b/tests/source/configs/fn_args_layout/vertical.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Vertical
+// rustfmt-fn_args_layout: Vertical
 // Function arguments density
 
 trait Lorem {
diff --git a/tests/source/fn-custom-7.rs b/tests/source/fn-custom-7.rs
index d76125234fa..d5330196bf7 100644
--- a/tests/source/fn-custom-7.rs
+++ b/tests/source/fn-custom-7.rs
@@ -1,5 +1,5 @@
 // rustfmt-normalize_comments: true
-// rustfmt-fn_args_density: Vertical
+// rustfmt-fn_args_layout: Vertical
 // rustfmt-brace_style: AlwaysNextLine
 
 // Case with only one variable.
diff --git a/tests/source/fn-custom.rs b/tests/source/fn-custom.rs
index b8d734bfbaf..77ced4c5e0e 100644
--- a/tests/source/fn-custom.rs
+++ b/tests/source/fn-custom.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Compressed
+// rustfmt-fn_args_layout: Compressed
 // Test some of the ways function signatures can be customised.
 
 // Test compressed layout of args.
diff --git a/tests/source/fn_args_density-vertical.rs b/tests/source/fn_args_layout-vertical.rs
similarity index 96%
rename from tests/source/fn_args_density-vertical.rs
rename to tests/source/fn_args_layout-vertical.rs
index b61c337dfb9..759bc83d015 100644
--- a/tests/source/fn_args_density-vertical.rs
+++ b/tests/source/fn_args_layout-vertical.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Vertical
+// rustfmt-fn_args_layout: Vertical
 
 // Empty list should stay on one line.
 fn do_bar(
diff --git a/tests/target/configs/fn_args_density/compressed.rs b/tests/target/configs/fn_args_layout/compressed.rs
similarity index 93%
rename from tests/target/configs/fn_args_density/compressed.rs
rename to tests/target/configs/fn_args_layout/compressed.rs
index 99283722bee..f189446e25d 100644
--- a/tests/target/configs/fn_args_density/compressed.rs
+++ b/tests/target/configs/fn_args_layout/compressed.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Compressed
+// rustfmt-fn_args_layout: Compressed
 // Function arguments density
 
 trait Lorem {
diff --git a/tests/target/configs/fn_args_density/tall.rs b/tests/target/configs/fn_args_layout/tall.rs
similarity index 94%
rename from tests/target/configs/fn_args_density/tall.rs
rename to tests/target/configs/fn_args_layout/tall.rs
index 6ee43b41a19..20f308973ac 100644
--- a/tests/target/configs/fn_args_density/tall.rs
+++ b/tests/target/configs/fn_args_layout/tall.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Tall
+// rustfmt-fn_args_layout: Tall
 // Function arguments density
 
 trait Lorem {
diff --git a/tests/target/configs/fn_args_density/vertical.rs b/tests/target/configs/fn_args_layout/vertical.rs
similarity index 94%
rename from tests/target/configs/fn_args_density/vertical.rs
rename to tests/target/configs/fn_args_layout/vertical.rs
index d48b3492452..6c695a75df9 100644
--- a/tests/target/configs/fn_args_density/vertical.rs
+++ b/tests/target/configs/fn_args_layout/vertical.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Vertical
+// rustfmt-fn_args_layout: Vertical
 // Function arguments density
 
 trait Lorem {
diff --git a/tests/target/fn-custom-7.rs b/tests/target/fn-custom-7.rs
index f98150c4291..2c20ac5a752 100644
--- a/tests/target/fn-custom-7.rs
+++ b/tests/target/fn-custom-7.rs
@@ -1,5 +1,5 @@
 // rustfmt-normalize_comments: true
-// rustfmt-fn_args_density: Vertical
+// rustfmt-fn_args_layout: Vertical
 // rustfmt-brace_style: AlwaysNextLine
 
 // Case with only one variable.
diff --git a/tests/target/fn-custom.rs b/tests/target/fn-custom.rs
index bf87553dedc..2eb2a973d24 100644
--- a/tests/target/fn-custom.rs
+++ b/tests/target/fn-custom.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Compressed
+// rustfmt-fn_args_layout: Compressed
 // Test some of the ways function signatures can be customised.
 
 // Test compressed layout of args.
diff --git a/tests/target/fn_args_density-vertical.rs b/tests/target/fn_args_layout-vertical.rs
similarity index 96%
rename from tests/target/fn_args_density-vertical.rs
rename to tests/target/fn_args_layout-vertical.rs
index 477a48cc35f..da0ac981d87 100644
--- a/tests/target/fn_args_density-vertical.rs
+++ b/tests/target/fn_args_layout-vertical.rs
@@ -1,4 +1,4 @@
-// rustfmt-fn_args_density: Vertical
+// rustfmt-fn_args_layout: Vertical
 
 // Empty list should stay on one line.
 fn do_bar() -> u8 {