Support where clause predicates at different indentations

src/config.rs

@@ -93,6 +93,7 @@ create_config! {
     fn_arg_indent: BlockIndentStyle,
     where_indent: BlockIndentStyle, // Visual will be treated like Tabbed
     where_layout: ListTactic,
+    where_pred_indent: BlockIndentStyle,
     generics_indent: BlockIndentStyle,
     struct_trailing_comma: SeparatorTactic,
     struct_lit_trailing_comma: SeparatorTactic,
@@ -122,6 +123,7 @@ impl Default for Config {
             fn_arg_indent: BlockIndentStyle::Visual,
             where_indent: BlockIndentStyle::Tabbed,
             where_layout: ListTactic::Vertical,
+            where_pred_indent: BlockIndentStyle::Visual,
             generics_indent: BlockIndentStyle::Visual,
             struct_trailing_comma: SeparatorTactic::Vertical,
             struct_lit_trailing_comma: SeparatorTactic::Vertical,

src/items.rs

@@ -806,8 +806,16 @@ impl<'a> FmtVisitor<'a> {
         };
 
         let context = self.get_context();
-        // 6 = "where ".len()
-        let offset = indent + extra_indent + 6;
+
+        let offset = match self.config.where_pred_indent {
+            BlockIndentStyle::Inherit => indent + extra_indent,
+            BlockIndentStyle::Tabbed => indent + extra_indent + config.tab_spaces,
+            // 6 = "where ".len()
+            BlockIndentStyle::Visual => indent + extra_indent + 6,
+        };
+        // FIXME: if where_pred_indent != Visual, then the budgets below might
+        // be out by a char or two.
+
         let budget = self.config.ideal_width + self.config.leeway - offset;
         let span_start = span_for_where_pred(&where_clause.predicates[0]).lo;
         let items = itemize_list(self.codemap,

tests/config/small_tabs.toml

@@ -10,6 +10,7 @@ fn_args_layout = "Tall"
 fn_arg_indent = "Visual"
 where_indent = "Tabbed"
 where_layout = "Vertical"
+where_pred_indent = "Visual"
 generics_indent = "Visual"
 struct_trailing_comma = "Vertical"
 struct_lit_trailing_comma = "Vertical"

tests/source/fn-custom-4.rs

@@ -0,0 +1,6 @@
+// rustfmt-where_pred_indent: Tabbed
+// Test different indents.
+
+fn qux() where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT {
+    baz();
+}

tests/source/fn-custom-5.rs

@@ -0,0 +1,6 @@
+// rustfmt-where_pred_indent: Inherit
+// Test different indents.
+
+fn qux() where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT, X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT {
+    baz();
+}

tests/target/fn-custom-4.rs

@@ -0,0 +1,11 @@
+// rustfmt-where_pred_indent: Tabbed
+// Test different indents.
+
+fn qux()
+    where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+        X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+        X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+        X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT
+{
+    baz();
+}

tests/target/fn-custom-5.rs

@@ -0,0 +1,11 @@
+// rustfmt-where_pred_indent: Inherit
+// Test different indents.
+
+fn qux()
+    where X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT,
+    X: TTTTTTTTTTTTTTTTTTTTTTTTTTTT
+{
+    baz();
+}