Clamp width settings to max_width before warning about exceeding it

Within a macro scope, max_width is reduced, which can trigger warnings
if it is reduced below some other width setting (e.g. struct_lit_width.)
Width settings were already being clamped to max_width, but only after
the warning fired.  The order is now reversed.

src/config/config_type.rs

@@ -431,18 +431,24 @@ macro_rules! create_config {
                     heuristic_value: usize,
                     config_key: &str,
                 | -> usize {
-                    if !was_set {
-                        return heuristic_value;
-                    }
-                    if override_value > max_width {
+                    let value = if !was_set {
+                        heuristic_value
+                    } else {
+                        override_value
+                    };
+
+                    let value = value.min(max_width);
+
+                    if value > max_width {
                         eprintln!(
                             "`{0}` cannot have a value that exceeds `max_width`. \
                             `{0}` will be set to the same value as `max_width`",
                             config_key,
                         );
-                        return max_width;
+                        max_width
+                    } else {
+                        value
                     }
-                    override_value
                 };
 
                 let fn_call_width = get_width_value(

src/config/mod.rs

@@ -680,6 +680,21 @@ mod test {
         assert_eq!(config.was_set().verbose(), false);
     }
 
+    #[test]
+    fn test_clamp_to_max_width() {
+        let toml = r#"
+            max_width = 100
+            struct_lit_width = 200
+        "#;
+        let mut config = Config::from_toml(toml, Path::new("./rustfmt.toml")).unwrap();
+        assert_eq!(config.struct_lit_width(), config.max_width());
+
+        // simulate entering a macro scope
+        let new = config.max_width() - 4;
+        config.set().max_width(new);
+        assert_eq!(config.struct_lit_width(), config.max_width());
+    }
+
     const PRINT_DOCS_STABLE_OPTION: &str = "stable_option <boolean> Default: false";
     const PRINT_DOCS_UNSTABLE_OPTION: &str = "unstable_option <boolean> Default: false (unstable)";
     const PRINT_DOCS_PARTIALLY_UNSTABLE_OPTION: &str =
@@ -1049,10 +1064,10 @@ make_backup = false
                 max_width = 100
             "#;
             let config = Config::from_toml(toml, Path::new("./rustfmt.toml")).unwrap();
-            assert_eq!(config.array_width(), usize::MAX);
-            assert_eq!(config.attr_fn_like_width(), usize::MAX);
-            assert_eq!(config.chain_width(), usize::MAX);
-            assert_eq!(config.fn_call_width(), usize::MAX);
+            assert_eq!(config.array_width(), config.max_width());
+            assert_eq!(config.attr_fn_like_width(), config.max_width());
+            assert_eq!(config.chain_width(), config.max_width());
+            assert_eq!(config.fn_call_width(), config.max_width());
             assert_eq!(config.single_line_if_else_max_width(), 0);
             assert_eq!(config.struct_lit_width(), 0);
             assert_eq!(config.struct_variant_width(), 0);