Ditch unecessary “weak maps”.

The search set for the weak maps we’re using gets untenable since it’s
a flat list of pointers for _all_ results.

It feels like a reasonable concession to hang data off of a unique
symbol key. These are non-enumerable (unless specifically trying to
enumerate symbols), which feels internal enough.

Additionally, we can just return frozen results from our tagged template
functions — it’s just passing back information from the user, so it’s
hardly even a “leak” of our inner abstractions.

test/test-template-engine.js

@@ -541,6 +541,27 @@ describe('html rendering', () => {
     assert(container.children[0].localName === 'textarea');
     container.remove();
   });
+
+  it('renders the same template result multiple times for', () => {
+    const rawResult = html`<div id="target"></div>`;
+    const container1 = document.createElement('div');
+    const container2 = document.createElement('div');
+    document.body.append(container1, container2);
+    render(container1, rawResult);
+    render(container2, rawResult);
+    assert(!!container1.querySelector('#target'));
+    assert(!!container2.querySelector('#target'));
+    render(container1, null);
+    render(container2, null);
+    assert(!container1.querySelector('#target'));
+    assert(!container2.querySelector('#target'));
+    render(container1, rawResult);
+    render(container2, rawResult);
+    assert(!!container1.querySelector('#target'));
+    assert(!!container2.querySelector('#target'));
+    container1.remove();
+    container2.remove();
+  });
 });
 
 describe('html updaters', () => {
@@ -1081,6 +1102,16 @@ describe('svg updaters', () => {
 
 describe('rendering errors', () => {
   describe('templating', () => {
+    it('throws when given container is not a node', () => {
+      let error;
+      try {
+        render({}, html``);
+      } catch (e) {
+        error = e;
+      }
+      assert(error?.message === 'Unexpected non-node render container "[object Object]".', error.message);
+    });
+
     it('throws when attempting to interpolate within a style tag', () => {
       const getTemplate = ({ color }) => {
         return html`
@@ -1156,12 +1187,12 @@ describe('rendering errors', () => {
     });
 
     it('throws for unquoted attributes', () => {
-      const templateResultReference = html`<div id="target" not-ok=${'foo'}>Gotta double-quote those.</div>`;
+      const rawResult = html`<div id="target" not-ok=${'foo'}>Gotta double-quote those.</div>`;
       const container = document.createElement('div');
       document.body.append(container);
       let error;
       try {
-        render(container, templateResultReference);
+        render(container, rawResult);
       } catch (e) {
         error = e;
       }
@@ -1170,12 +1201,12 @@ describe('rendering errors', () => {
     });
 
     it('throws for single-quoted attributes', () => {
-      const templateResultReference = html`\n<div id="target" not-ok='${'foo'}'>Gotta double-quote those.</div>`;
+      const rawResult = html`\n<div id="target" not-ok='${'foo'}'>Gotta double-quote those.</div>`;
       const container = document.createElement('div');
       document.body.append(container);
       let error;
       try {
-        render(container, templateResultReference);
+        render(container, rawResult);
       } catch (e) {
         error = e;
       }
@@ -1184,12 +1215,12 @@ describe('rendering errors', () => {
     });
 
     it('throws for unquoted properties', () => {
-      const templateResultReference = html`\n\n\n<div id="target" .notOk=${'foo'}>Gotta double-quote those.</div>`;
+      const rawResult = html`\n\n\n<div id="target" .notOk=${'foo'}>Gotta double-quote those.</div>`;
       const container = document.createElement('div');
       document.body.append(container);
       let error;
       try {
-        render(container, templateResultReference);
+        render(container, rawResult);
       } catch (e) {
         error = e;
       }
@@ -1198,12 +1229,12 @@ describe('rendering errors', () => {
     });
 
     it('throws for single-quoted properties', () => {
-      const templateResultReference = html`<div id="target" .notOk='${'foo'}'>Gotta double-quote those.</div>`;
+      const rawResult = html`<div id="target" .notOk='${'foo'}'>Gotta double-quote those.</div>`;
       const container = document.createElement('div');
       document.body.append(container);
       let error;
       try {
-        render(container, templateResultReference);
+        render(container, rawResult);
       } catch (e) {
         error = e;
       }
@@ -1228,24 +1259,6 @@ describe('rendering errors', () => {
       assert(actual === expected, actual);
       container.remove();
     });
-
-    it('throws for re-injection of template result', () => {
-      const templateResultReference = html`<div id="target"></div>`;
-      const container = document.createElement('div');
-      document.body.append(container);
-      render(container, templateResultReference);
-      assert(!!container.querySelector('#target'));
-      render(container, null);
-      assert(!container.querySelector('#target'));
-      let error;
-      try {
-        render(container, templateResultReference);
-      } catch (e) {
-        error = e;
-      }
-      assert(error?.message === 'Unexpected re-injection of template result.', error.message);
-      container.remove();
-    });
   });
 
   describe('ifDefined', () => {