finish up the grand geom stabilization with ring and some docs.

regenerated everything from scratch. one effect is more parking
blockface gets matched onto border roads, but that's fine.

convert_osm/src/clip.rs

@@ -9,7 +9,7 @@ pub fn clip_map(map: &mut RawMap, timer: &mut Timer) {
 
     // So we can use retain_btreemap without borrowing issues
     let boundary_polygon = map.boundary_polygon.clone();
-    let boundary_ring = Ring::new(boundary_polygon.points().clone());
+    let boundary_ring = Ring::must_new(boundary_polygon.points().clone());
 
     // This is kind of indirect and slow, but first pass -- just remove roads that start or end
     // outside the boundary polygon.

convert_osm/src/osm_reader.rs

@@ -180,7 +180,7 @@ pub fn extract_osm(
         }
     }
 
-    let boundary = Ring::new(map.boundary_polygon.points().clone());
+    let boundary = Ring::must_new(map.boundary_polygon.points().clone());
 
     let mut simple_turn_restrictions = Vec::new();
     let mut complicated_turn_restrictions = Vec::new();

data/MANIFEST.txt

@@ -3,22 +3,22 @@ data/input/austin/osm/downtown_atx.osm,a30b0f460a481598e494f16a9d07a822,https://
 data/input/austin/osm/huge_austin.osm,fb166029fc8006bd20dc959fbbbde3b6,https://www.dropbox.com/s/4x421o9o8px0m6o/huge_austin.osm.zip?dl=0
 data/input/krakow/osm/huge_krakow.osm,0b098456c8ae844ff240ca9fe3b617d1,https://www.dropbox.com/s/fe2e8qzd4g5tkoy/huge_krakow.osm.zip?dl=0
 data/input/krakow/osm/malopolskie-latest.osm.pbf,d848a278092001aaab3ced09de4d98ff,https://www.dropbox.com/s/ia2uwy3z52r6hpe/malopolskie-latest.osm.pbf.zip?dl=0
-data/input/raw_maps/ballard.bin,fea0486d3925c7ffce54d0e21139ab75,https://www.dropbox.com/s/dfbtfu6qq7shj9t/ballard.bin.zip?dl=0
+data/input/raw_maps/ballard.bin,4d72687ab860144d19ae3f1328f2b61d,https://www.dropbox.com/s/dkxhkir85rtm906/ballard.bin.zip?dl=0
-data/input/raw_maps/downtown.bin,5da76c12b035bcde09d0735c6673d4ae,https://www.dropbox.com/s/f3jz7qk6xiij5po/downtown.bin.zip?dl=0
+data/input/raw_maps/downtown.bin,48886494c43fd7b9db12a53f990dcb4f,https://www.dropbox.com/s/87rpndh1yudrlxb/downtown.bin.zip?dl=0
 data/input/raw_maps/downtown_atx.bin,2995df6f32feb8135fbb1126b52402ba,https://www.dropbox.com/s/csuzjqhhbtw657x/downtown_atx.bin.zip?dl=0
 data/input/raw_maps/huge_austin.bin,fb671ea39ea254207c334b5662763433,https://www.dropbox.com/s/91i763larrbmx7z/huge_austin.bin.zip?dl=0
 data/input/raw_maps/huge_krakow.bin,978426f967f122675ba530edc94b43e3,https://www.dropbox.com/s/5l9ojm1lfq32otz/huge_krakow.bin.zip?dl=0
-data/input/raw_maps/huge_seattle.bin,e7e49c7421e1343371ab06dc9e3dd64b,https://www.dropbox.com/s/dlajjc94bmxf07p/huge_seattle.bin.zip?dl=0
+data/input/raw_maps/huge_seattle.bin,95798750903b3a7c35f165aaf3e39c91,https://www.dropbox.com/s/5pumdup46zmhb34/huge_seattle.bin.zip?dl=0
-data/input/raw_maps/lakeslice.bin,95ed0a848ed098c068ada54db04c9495,https://www.dropbox.com/s/g1y26xudv7rkmko/lakeslice.bin.zip?dl=0
+data/input/raw_maps/lakeslice.bin,28ede305a1e45a4298b8d10503324905,https://www.dropbox.com/s/j707o0ka1k4ixgk/lakeslice.bin.zip?dl=0
-data/input/raw_maps/montlake.bin,1840e685f91589cf267f146f43878c47,https://www.dropbox.com/s/p5itfq7zioz2b3r/montlake.bin.zip?dl=0
+data/input/raw_maps/montlake.bin,712532a30baa5225aca621fd1f1f7f0a,https://www.dropbox.com/s/evwmldb5872nf0u/montlake.bin.zip?dl=0
-data/input/raw_maps/south_seattle.bin,bb870ffa8bd159a7ce9dca83216ac0b0,https://www.dropbox.com/s/v405rk7wm7luc0o/south_seattle.bin.zip?dl=0
+data/input/raw_maps/south_seattle.bin,5eb52175e7fd06da3fc3e93fc2ca88fc,https://www.dropbox.com/s/jfc4ht5ydm05j8y/south_seattle.bin.zip?dl=0
-data/input/raw_maps/udistrict.bin,ae242a89a2b83b2b9fc115dea0c40256,https://www.dropbox.com/s/vefz3ozb7od9xdf/udistrict.bin.zip?dl=0
+data/input/raw_maps/udistrict.bin,a45f45140c03da4abf8d698cda580133,https://www.dropbox.com/s/plspsqay9c77fwz/udistrict.bin.zip?dl=0
 data/input/raw_maps/west_seattle.bin,4784c2eeebd11c6c180d11eda73cf1e1,https://www.dropbox.com/s/6lp4foo4l7g487n/west_seattle.bin.zip?dl=0
-data/input/screenshots/downtown.zip,f1cb474323244ef7a31971e3d5b25a12,https://www.dropbox.com/s/qawd35wz62m2acl/downtown.zip.zip?dl=0
+data/input/screenshots/downtown.zip,bdad536ddb7f0e5aab912433b3c28e69,https://www.dropbox.com/s/qawd35wz62m2acl/downtown.zip.zip?dl=0
-data/input/screenshots/huge_krakow.zip,cfc8fe595097fed224d369f2c647443c,https://www.dropbox.com/s/dbzon7k5ukndtza/huge_krakow.zip.zip?dl=0
+data/input/screenshots/huge_krakow.zip,8edcb39fedadb7991ab2959064c98629,https://www.dropbox.com/s/dbzon7k5ukndtza/huge_krakow.zip.zip?dl=0
-data/input/screenshots/lakeslice.zip,37ad352dbe42ce4aea0ba0a67067d451,https://www.dropbox.com/s/z0z96lsn7bunqfy/lakeslice.zip.zip?dl=0
+data/input/screenshots/lakeslice.zip,73c0ed5add17f8c49218b1c22ee464cc,https://www.dropbox.com/s/z0z96lsn7bunqfy/lakeslice.zip.zip?dl=0
-data/input/screenshots/montlake.zip,c8b016f00792ef23b9fae44956d2d86c,https://www.dropbox.com/s/r9vkgwesqklfuq2/montlake.zip.zip?dl=0
+data/input/screenshots/montlake.zip,fbc945c0869c2b85ccfb1fef4340ba2e,https://www.dropbox.com/s/r9vkgwesqklfuq2/montlake.zip.zip?dl=0
-data/input/screenshots/udistrict.zip,584036034b44708da6ae006b2f40fa3b,https://www.dropbox.com/s/ecnt1tyza48y9o2/udistrict.zip.zip?dl=0
+data/input/screenshots/udistrict.zip,c7a7a258e3d0a417ada55f70c897d4d3,https://www.dropbox.com/s/ecnt1tyza48y9o2/udistrict.zip.zip?dl=0
 data/input/seattle/N47W122.hgt,0db4e23e51f7680538b0bbbc72208e07,https://www.dropbox.com/s/mmb4mgutwotijdw/N47W122.hgt.zip?dl=0
 data/input/seattle/blockface.bin,add872bab9040ae911366328a230f8b5,https://www.dropbox.com/s/rxd2care60tbe75/blockface.bin.zip?dl=0
 data/input/seattle/blockface.kml,350bd9e59bf2af4e885a7c0741e6ee6b,https://www.dropbox.com/s/ukknmpjdvilncq9/blockface.kml.zip?dl=0
@@ -33,30 +33,30 @@ data/input/seattle/osm/south_seattle.osm,2a20b3549004a3d37ef962baf07fbf93,https:
 data/input/seattle/osm/udistrict.osm,769388ffc0d73c6a149ed79698e2b8f3,https://www.dropbox.com/s/3v6axtyuofqatit/udistrict.osm.zip?dl=0
 data/input/seattle/osm/washington-latest.osm.pbf,ac31d2a9d3a109f4467e5f64b5922509,https://www.dropbox.com/s/eilk9soyod3war6/washington-latest.osm.pbf.zip?dl=0
 data/input/seattle/osm/west_seattle.osm,b87c760bd512c4302846519ed052ad5a,https://www.dropbox.com/s/qhtkotrtp7ilmy1/west_seattle.osm.zip?dl=0
-data/input/seattle/parcels.bin,1cfdc485a35df9edce7b24e5c17b2977,https://www.dropbox.com/s/s977yzbcds355nv/parcels.bin.zip?dl=0
+data/input/seattle/parcels.bin,fbaa5480e614e7f59a9e958f92a12526,https://www.dropbox.com/s/cy88qmctgya2g76/parcels.bin.zip?dl=0
 data/input/seattle/parcels_urbansim.txt,db63d7d606e8702d12f9399e87e6a00f,https://www.dropbox.com/s/6g8rbsf200dssj3/parcels_urbansim.txt.zip?dl=0
 data/input/seattle/popdat.bin,ad38e1f20ce71f488112fe81e32798d2,https://www.dropbox.com/s/ajqii1qpfke8063/popdat.bin.zip?dl=0
 data/input/seattle/trips_2014.csv,d4a8e733045b28c0385fb81359d6df03,https://www.dropbox.com/s/5ppravwmk6bf20d/trips_2014.csv.zip?dl=0
 data/system/cities/seattle.bin,9ed9ff25b3f3941fecf530b3815a1b05,https://www.dropbox.com/s/nwb29tt4koqk6um/seattle.bin.zip?dl=0
-data/system/maps/ballard.bin,b98c9b698d876ebadd34bbcb541630d3,https://www.dropbox.com/s/ocv4p7dzrxcogyq/ballard.bin.zip?dl=0
+data/system/maps/ballard.bin,d4ab6ceb6905dfa14b2aaac99c495eff,https://www.dropbox.com/s/too29h0nr6s64wm/ballard.bin.zip?dl=0
-data/system/maps/downtown.bin,f951b7ca011b91f062334a94585b7083,https://www.dropbox.com/s/ww7jzqlbpxur8l6/downtown.bin.zip?dl=0
+data/system/maps/downtown.bin,6b7735033169acdb4c1429b084632de5,https://www.dropbox.com/s/8s6pjo91spchkfx/downtown.bin.zip?dl=0
 data/system/maps/downtown_atx.bin,700a4a78af42e37ef1245e4fc63ce0c4,https://www.dropbox.com/s/ixijn46f07zizzi/downtown_atx.bin.zip?dl=0
 data/system/maps/huge_austin.bin,f7ea14d6b616a6ca9a63ac4460b0a2a0,https://www.dropbox.com/s/5jlbbinjp4132rp/huge_austin.bin.zip?dl=0
 data/system/maps/huge_krakow.bin,f87b77708170bafa72331cccc6df57b6,https://www.dropbox.com/s/friayproln1gtig/huge_krakow.bin.zip?dl=0
-data/system/maps/huge_seattle.bin,4086044e523651a631f0745e73238bb8,https://www.dropbox.com/s/aj0h8igtskfths3/huge_seattle.bin.zip?dl=0
+data/system/maps/huge_seattle.bin,05214611240c878306f351b76d07db3b,https://www.dropbox.com/s/xakfwfqbcyeznuy/huge_seattle.bin.zip?dl=0
-data/system/maps/lakeslice.bin,ea5e918b7b70db2c8e484f8666c4737b,https://www.dropbox.com/s/p6r64ujz81vx7vd/lakeslice.bin.zip?dl=0
+data/system/maps/lakeslice.bin,ecd6b3b127982eb9b42530da2bb0887b,https://www.dropbox.com/s/dkmf2qaa991uxym/lakeslice.bin.zip?dl=0
-data/system/maps/montlake.bin,032f96ae28a2db2d6b4aa848469e9aea,https://www.dropbox.com/s/rjei8n91qil1bhw/montlake.bin.zip?dl=0
+data/system/maps/montlake.bin,cb2246cb15edc0553f5b03af4886471c,https://www.dropbox.com/s/0dnysbp2h7wdaf4/montlake.bin.zip?dl=0
-data/system/maps/south_seattle.bin,c967a5d372ef7298a711fc213244ccd8,https://www.dropbox.com/s/nynh73cxqggeuj3/south_seattle.bin.zip?dl=0
+data/system/maps/south_seattle.bin,174a44c25848f36d82a59644ef56582e,https://www.dropbox.com/s/cu8exdobcdaj6sm/south_seattle.bin.zip?dl=0
-data/system/maps/udistrict.bin,a9a320f182af78d235af98a78aa0646c,https://www.dropbox.com/s/92joyhk29cqoipk/udistrict.bin.zip?dl=0
+data/system/maps/udistrict.bin,c0cf3f4758ebd9faef843cf587b32a99,https://www.dropbox.com/s/z38hxojx3x8qpvl/udistrict.bin.zip?dl=0
 data/system/maps/west_seattle.bin,ccfb1547ffceaa8a635b12252951ce8f,https://www.dropbox.com/s/x9o4lg7fgvy5kr2/west_seattle.bin.zip?dl=0
-data/system/prebaked_results/lakeslice/weekday.bin,3bcb09e1d6ddeed75e3baf3b6b476e5c,https://www.dropbox.com/s/5odd5kdxn0caodk/weekday.bin.zip?dl=0
+data/system/prebaked_results/lakeslice/weekday.bin,6cb89d0581ad0d78cd7644a882ab0528,https://www.dropbox.com/s/frg14z9f90qrk8v/weekday.bin.zip?dl=0
-data/system/prebaked_results/montlake/car vs bike contention.bin,d3e42a758ba4e10e6143c8f8370a638f,https://www.dropbox.com/s/jefg0ikjy9dsrdd/car%20vs%20bike%20contention.bin.zip?dl=0
+data/system/prebaked_results/montlake/car vs bike contention.bin,bd7bbdee559245ed5dd85ddd67165cf9,https://www.dropbox.com/s/jefg0ikjy9dsrdd/car%20vs%20bike%20contention.bin.zip?dl=0
-data/system/prebaked_results/montlake/weekday.bin,979af6c1db9f5bf31a3cf12301c4c6f9,https://www.dropbox.com/s/0duohjtnbj5y7gc/weekday.bin.zip?dl=0
+data/system/prebaked_results/montlake/weekday.bin,be76cdebe55527b2e19e1c09f9540426,https://www.dropbox.com/s/gzxg2orfu8z9s6x/weekday.bin.zip?dl=0
-data/system/scenarios/ballard/weekday.bin,f6d7dac5af0f35a6ae5589d3943be789,https://www.dropbox.com/s/klvs4wkauh00xud/weekday.bin.zip?dl=0
+data/system/scenarios/ballard/weekday.bin,b1993a9f154cf88c78884eb96ee28a08,https://www.dropbox.com/s/2sf37gu7nur9o37/weekday.bin.zip?dl=0
-data/system/scenarios/downtown/weekday.bin,2b4506c9aab41a0a12f8d0ef769db492,https://www.dropbox.com/s/swmss3vyrrjnv6n/weekday.bin.zip?dl=0
+data/system/scenarios/downtown/weekday.bin,67c8345c4340cbd0a69d3c079c1c6b6c,https://www.dropbox.com/s/kasxsyett83oo03/weekday.bin.zip?dl=0
-data/system/scenarios/huge_seattle/weekday.bin,30cf8491099a33c758aa76c31267bd13,https://www.dropbox.com/s/a20dujaxnwhe2aj/weekday.bin.zip?dl=0
+data/system/scenarios/huge_seattle/weekday.bin,102b72c09c63042dc7ca3c143bf7508a,https://www.dropbox.com/s/ebvg1zgv2ywnndf/weekday.bin.zip?dl=0
-data/system/scenarios/lakeslice/weekday.bin,19812c16dc90945f5c3659b47c1c55e8,https://www.dropbox.com/s/00cjax1g3bcmwvf/weekday.bin.zip?dl=0
+data/system/scenarios/lakeslice/weekday.bin,0d86fa1518f5e06942c0b2b8869b9000,https://www.dropbox.com/s/0cuc7urc0fsgqi5/weekday.bin.zip?dl=0
-data/system/scenarios/montlake/weekday.bin,ee5359d37d1d9446578d34c3b97b9266,https://www.dropbox.com/s/bx6sv6rogt2alyq/weekday.bin.zip?dl=0
+data/system/scenarios/montlake/weekday.bin,3c19364da831e3f81fed81b6edc1a844,https://www.dropbox.com/s/8ypid1mus95ivni/weekday.bin.zip?dl=0
-data/system/scenarios/south_seattle/weekday.bin,9b84537fb47831d6b65f81dcb947600d,https://www.dropbox.com/s/i36o01uv6ud8rj3/weekday.bin.zip?dl=0
+data/system/scenarios/south_seattle/weekday.bin,16f5512c24bc140b6d333a44819936d2,https://www.dropbox.com/s/rvyypxoc0awubn1/weekday.bin.zip?dl=0
-data/system/scenarios/udistrict/weekday.bin,6c08853e72f8fc65b25b69639cb59464,https://www.dropbox.com/s/3c0tlq9k8niz0pr/weekday.bin.zip?dl=0
+data/system/scenarios/udistrict/weekday.bin,25bf5370f905ce57c017028a33612c4e,https://www.dropbox.com/s/msb70poj5dl29q2/weekday.bin.zip?dl=0
-data/system/scenarios/west_seattle/weekday.bin,48a9b04d69948436c8eb89f943e36b5d,https://www.dropbox.com/s/8jq9rs6dom8t0y9/weekday.bin.zip?dl=0
+data/system/scenarios/west_seattle/weekday.bin,089ee9b267bafc860f8c6952a69f3efe,https://www.dropbox.com/s/l3lfj8gk232cyrl/weekday.bin.zip?dl=0

docs/dev.md

@@ -46,9 +46,6 @@ One-time setup:
     experience, so they're hidden for now.
   - `cargo run --bin game -- --tutorial=12` starts somewhere in the tutorial
   - Adding `--edits='name of edits'` starts with edits applied to the map.
-- All code is automatically formatted using
-  https://github.com/rust-lang/rustfmt; please run `cargo +nightly fmt` before
-  sending a PR. (You have to install the nightly toolchain just for fmt)
 - More random notes [here](/docs/misc_dev_tricks.md)
 
 ## Downloading more cities
@@ -139,3 +136,24 @@ Common utilities:
 - `abstutil`: a grab-bag of IO helpers, timing and logging utilities, etc
 - `geom`: types for GPS and map-space points, lines, angles, polylines,
   polygons, circles, durations, speeds
+
+## Code conventions
+
+All code is automatically formatted using https://github.com/rust-lang/rustfmt;
+please run `cargo +nightly fmt` before sending a PR. (You have to install the
+nightly toolchain just for fmt)
+
+The error handling is unfortunately inconsistent. The goal is to gracefully
+degrade instead of crashing the game. If a crash does happen, make sure the logs
+will have enough context to reproduce and debug. For example, giving up when
+some geometry problem happens isn't ideal, but at least make sure to print the
+road / agent IDs or whatever will help find the problem. It's fine to crash
+during map importing, since the player won't deal with this, and loudly stopping
+problems is useful. It's also fine to crash when initially constructing all of
+the renderable map objects, because this crash will consistently happen at
+startup-time and be noticed by somebody developing before a player gets to it.
+
+I have lots of thoughts about testing that I haven't written anywhere yet.
+You'll surely note the lack of unit tests. If it bothers you, let's talk about
+what tests should exist. In the meantime, note lots of validation does happen
+via importing maps, running the prebaked scenarios, and screenshot diffing.

ezgui/src/managed.rs

@@ -421,7 +421,8 @@ impl Widget {
                 batch.push(
                     color,
                     Polygon::rounded_rectangle(width, height, self.layout.rounded_radius)
-                        .to_outline(Distance::meters(thickness)),
+                        .to_outline(Distance::meters(thickness))
+                        .unwrap(),
                 );
             }
             self.bg = Some(ctx.upload(batch));

ezgui/src/widgets/dropdown.rs

@@ -130,7 +130,10 @@ impl<T: 'static + Clone> WidgetImpl for Dropdown<T> {
             let rect = Polygon::rounded_rectangle(width, height, Some(5.0));
             let draw_bg = g.upload(GeomBatch::from(vec![
                 (Color::grey(0.3), rect.clone()),
-                (Color::WHITE, rect.to_outline(Distance::meters(3.0))),
+                (
+                    Color::WHITE,
+                    rect.to_outline(Distance::meters(3.0)).unwrap(),
+                ),
             ]));
             g.fork(
                 Pt2D::new(0.0, 0.0),

game/src/common/city_picker.rs

@@ -54,7 +54,7 @@ impl CityPicker {
                 if &name == app.primary.map.get_name() {
                     batch.push(color.alpha(0.5), polygon.clone());
                 } else {
-                    batch.push(color, polygon.to_outline(Distance::meters(200.0)));
+                    batch.push(color, polygon.to_outline(Distance::meters(200.0)).unwrap());
                 }
                 regions.push((name, color, polygon.scale(zoom_no_scale_factor)));
             }

game/src/common/minimap.rs

@@ -300,7 +300,7 @@ impl Minimap {
         };
         g.draw_polygon(
             Color::BLACK,
-            &Ring::new(vec![
+            &Ring::must_new(vec![
                 Pt2D::new(x1, y1),
                 Pt2D::new(x2, y1),
                 Pt2D::new(x2, y2),

game/src/devtools/kml.rs

@@ -204,7 +204,7 @@ fn make_object(
     } else if pts[0] == *pts.last().unwrap() {
         // TODO Toggle between these better
         //Polygon::new(&pts)
-        Ring::new(pts).make_polygons(THICKNESS)
+        Ring::must_new(pts).make_polygons(THICKNESS)
     } else {
         let backup = pts[0];
         match PolyLine::new(pts) {

game/src/devtools/story.rs

@@ -464,7 +464,7 @@ impl Marker {
         } else {
             let poly = Polygon::new(&pts);
             batch.push(Color::RED.alpha(0.8), poly.clone());
-            if let Some(o) = poly.maybe_to_outline(Distance::meters(1.0)) {
+            if let Ok(o) = poly.to_outline(Distance::meters(1.0)) {
                 batch.push(Color::RED, o);
             }
             // TODO Refactor
@@ -591,9 +591,9 @@ fn simplify(mut raw: Vec<Pt2D>) -> Ring {
             downsampled.push(Pt2D::new(pt.x, pt.y));
         }
         downsampled.push(downsampled[0]);
-        Ring::new(downsampled)
+        Ring::must_new(downsampled)
     } else {
         raw.push(raw[0]);
-        Ring::new(raw)
+        Ring::must_new(raw)
     }
 }

game/src/layer/traffic.rs

@@ -498,13 +498,16 @@ impl TrafficJams {
             app.primary.sim.delayed_intersections(Duration::minutes(5)),
         ) {
             cnt += 1;
-            unzoomed.push(Color::RED, boundary.to_outline(Distance::meters(5.0)));
+            unzoomed.push(
+                Color::RED,
+                boundary.to_outline(Distance::meters(5.0)).unwrap(),
+            );
             unzoomed.push(Color::RED.alpha(0.5), boundary.clone());
             unzoomed.push(Color::WHITE, epicenter.clone());
 
             zoomed.push(
                 Color::RED.alpha(0.4),
-                boundary.to_outline(Distance::meters(5.0)),
+                boundary.to_outline(Distance::meters(5.0)).unwrap(),
             );
             zoomed.push(Color::RED.alpha(0.3), boundary);
             zoomed.push(Color::WHITE.alpha(0.4), epicenter);

game/src/render/building.rs

@@ -40,7 +40,7 @@ impl DrawBuilding {
             cs.sidewalk,
             front_path_line.make_polygons(NORMAL_LANE_THICKNESS),
         );
-        if let Some(p) = bldg.polygon.maybe_to_outline(Distance::meters(0.1)) {
+        if let Ok(p) = bldg.polygon.to_outline(Distance::meters(0.1)) {
             outlines_batch.push(cs.building_outline, p);
         }
 
@@ -102,7 +102,7 @@ impl Renderable for DrawBuilding {
 
     fn get_outline(&self, map: &Map) -> Polygon {
         let b = map.get_b(self.id);
-        if let Some(p) = b.polygon.maybe_to_outline(OUTLINE_THICKNESS) {
+        if let Ok(p) = b.polygon.to_outline(OUTLINE_THICKNESS) {
             p
         } else {
             b.polygon.clone()

game/src/render/intersection.rs

@@ -163,7 +163,9 @@ impl Renderable for DrawIntersection {
     }
 
     fn get_outline(&self, map: &Map) -> Polygon {
-        map.get_i(self.id).polygon.to_outline(OUTLINE_THICKNESS)
+        let poly = &map.get_i(self.id).polygon;
+        poly.to_outline(OUTLINE_THICKNESS)
+            .unwrap_or_else(|_| poly.clone())
     }
 
     fn contains_pt(&self, pt: Pt2D, map: &Map) -> bool {

game/src/render/parking_lot.rs

@@ -100,7 +100,7 @@ impl Renderable for DrawParkingLot {
 
     fn get_outline(&self, map: &Map) -> Polygon {
         let pl = map.get_pl(self.id);
-        if let Some(p) = pl.polygon.maybe_to_outline(OUTLINE_THICKNESS) {
+        if let Ok(p) = pl.polygon.to_outline(OUTLINE_THICKNESS) {
             p
         } else {
             pl.polygon.clone()

game/src/render/traffic_signal.rs

@@ -368,7 +368,7 @@ pub fn make_signal_diagram(
 
             let mut hovered = GeomBatch::new();
             hovered.append(normal.clone());
-            hovered.push(Color::RED, bbox.to_outline(Distance::meters(5.0)));
+            hovered.push(Color::RED, bbox.to_outline(Distance::meters(5.0)).unwrap());
 
             Btn::custom(normal, hovered, bbox.clone()).build(
                 ctx,

game/src/sandbox/dashboards/summaries.rs

@@ -266,7 +266,7 @@ fn contingency_table(ctx: &mut EventCtx, app: &App, filter: &Filter) -> Widget {
         if num_savings > 0 {
             let height = (total_savings / max_y) * max_bar_height;
             let rect = Polygon::rectangle(bar_width, height).translate(x1, max_bar_height - height);
-            if let Some(o) = rect.maybe_to_outline(Distance::meters(1.5)) {
+            if let Ok(o) = rect.to_outline(Distance::meters(1.5)) {
                 outlines.push(o);
             }
             batch.push(Color::GREEN, rect.clone());
@@ -287,7 +287,7 @@ fn contingency_table(ctx: &mut EventCtx, app: &App, filter: &Filter) -> Widget {
             let height = (total_loss / max_y) * max_bar_height;
             let rect =
                 Polygon::rectangle(bar_width, height).translate(x1, total_height - max_bar_height);
-            if let Some(o) = rect.maybe_to_outline(Distance::meters(1.5)) {
+            if let Ok(o) = rect.to_outline(Distance::meters(1.5)) {
                 outlines.push(o);
             }
             batch.push(Color::RED, rect.clone());

geom/src/circle.rs

@@ -74,7 +74,7 @@ impl Circle {
         if false {
             let mut pts = Circle::new(center, radius).to_polygon().points().clone();
             pts.push(pts[0]);
-            return Ok(Ring::new(pts).make_polygons(thickness));
+            return Ok(Ring::must_new(pts).make_polygons(thickness));
         }
 
         // TODO Argh this one also leaves a little piece missing, but it looks less bad. Fine.

geom/src/polygon.rs

@@ -3,6 +3,7 @@ use geo::algorithm::area::Area;
 use geo::algorithm::convexhull::ConvexHull;
 use geo_booleanop::boolean::BooleanOp;
 use serde::{Deserialize, Serialize};
+use std::error::Error;
 use std::fmt;
 
 #[derive(Serialize, Deserialize, Clone, Debug)]
@@ -286,12 +287,8 @@ impl Polygon {
 
     // Only works for polygons that're formed from rings. Those made from PolyLines won't work, for
     // example.
-    pub fn to_outline(&self, thickness: Distance) -> Polygon {
+    pub fn to_outline(&self, thickness: Distance) -> Result<Polygon, Box<dyn Error>> {
-        Ring::new(self.points.clone()).make_polygons(thickness)
+        Ring::new(self.points.clone()).map(|r| r.make_polygons(thickness))
-    }
-
-    pub fn maybe_to_outline(&self, thickness: Distance) -> Option<Polygon> {
-        Ring::maybe_new(self.points.clone()).map(|r| r.make_polygons(thickness))
     }
 
     // Usually m^2, unless the polygon is in screen-space
@@ -301,7 +298,7 @@ impl Polygon {
 
     // Doesn't handle multiple crossings in and out.
     pub fn clip_polyline(&self, input: &PolyLine) -> Option<Vec<Pt2D>> {
-        let ring = Ring::new(self.points.clone());
+        let ring = Ring::must_new(self.points.clone());
         let hits = ring.all_intersections(input);
 
         if hits.len() == 0 {

geom/src/polyline.rs

@@ -93,7 +93,7 @@ impl PolyLine {
         side1.extend(side2);
         side1.push(side1[0]);
         side1.dedup();
-        Some(Ring::new(side1).make_polygons(boundary_width))
+        Some(Ring::must_new(side1).make_polygons(boundary_width))
     }
 
     pub fn reversed(&self) -> PolyLine {
@@ -556,7 +556,7 @@ impl PolyLine {
             let angle = slice.last_pt().angle_to(self.last_pt());
             vec![
                 p,
-                Ring::new(vec![
+                Ring::must_new(vec![
                     self.last_pt(),
                     self.last_pt()
                         .project_away(head_size, angle.rotate_degs(-135.0)),

geom/src/ring.rs

@@ -12,39 +12,16 @@ pub struct Ring {
 }
 
 impl Ring {
-    pub fn new(pts: Vec<Pt2D>) -> Ring {
+    pub fn new(pts: Vec<Pt2D>) -> Result<Ring, Box<dyn Error>> {
-        assert!(pts.len() >= 3);
+        if pts.len() < 3 {
-        assert_eq!(pts[0], *pts.last().unwrap());
+            return Err(format!("Can't make a ring with < 3 points").into());
-
-        // This checks no lines are too small. Could take the other approach and automatically
-        // squish down points here and make sure the final result is at least EPSILON_DIST.
-        // But probably better for the callers to do this -- they have better understanding of what
-        // needs to be squished down, why, and how.
-        if pts.windows(2).any(|pair| pair[0] == pair[1]) {
-            panic!("Ring has ~dupe adjacent pts: {:?}", pts);
         }
-
-        let result = Ring { pts };
-
-        let mut seen_pts = HashSet::new();
-        for pt in result.pts.iter().skip(1) {
-            seen_pts.insert(pt.to_hashable());
-        }
-        if seen_pts.len() != result.pts.len() - 1 {
-            panic!("Ring has repeat points: {}", result);
-        }
-
-        result
-    }
-
-    pub fn maybe_new(pts: Vec<Pt2D>) -> Option<Ring> {
-        assert!(pts.len() >= 3);
         if pts[0] != *pts.last().unwrap() {
-            return None;
+            return Err(format!("Can't make a ring with mismatching first/last points").into());
         }
 
         if pts.windows(2).any(|pair| pair[0] == pair[1]) {
-            return None;
+            return Err(format!("Ring has ~dupe adjacent pts").into());
         }
 
         let result = Ring { pts };
@@ -54,10 +31,13 @@ impl Ring {
             seen_pts.insert(pt.to_hashable());
         }
         if seen_pts.len() != result.pts.len() - 1 {
-            return None;
+            return Err(format!("Ring has repeat non-adjacent points").into());
         }
 
-        Some(result)
+        Ok(result)
+    }
+    pub fn must_new(pts: Vec<Pt2D>) -> Ring {
+        Ring::new(pts).unwrap()
     }
 
     pub fn make_polygons(&self, thickness: Distance) -> Polygon {
@@ -137,7 +117,7 @@ impl Ring {
             current.push(pt);
             if intersections.contains(&pt.to_hashable()) && current.len() > 1 {
                 if current[0] == pt {
-                    rings.push(Ring::new(current.drain(..).collect()));
+                    rings.push(Ring::must_new(current.drain(..).collect()));
                 } else {
                     polylines.push(PolyLine::new(current.drain(..).collect())?);
                 }

map_model/src/make/turns.rs

@@ -549,7 +549,7 @@ fn make_shared_sidewalk_corner(
 
     // TODO Something like this will be MUCH simpler and avoid going around the long way sometimes.
     if false {
-        return Ring::new(i.polygon.points().clone()).get_shorter_slice_btwn(corner1, corner2);
+        return Ring::must_new(i.polygon.points().clone()).get_shorter_slice_btwn(corner1, corner2);
     }
 
     // The order of the points here seems backwards, but it's because we scan from corner2