make "skip global checks" apply to the "only performed" rule

Author: bakkot

src/typechecker.ts

@@ -233,7 +233,10 @@ export function typecheck(spec: Spec) {
     .localEntries()
     .filter(e => e.type === 'op' && e.signature?.return != null) as AlgorithmBiblioEntry[];
   const onlyPerformed: OnlyPerformedMap = new Map(
-    AOs.filter(e => !isUnused(e.signature!.return!)).map(a => [a.aoid, null]),
+    AOs.filter(e => !e.skipGlobalChecks && !isUnused(e.signature!.return!)).map(a => [
+      a.aoid,
+      null,
+    ]),
   );
   const alwaysAssertedToBeNormal: AlwaysAssertedToBeNormalMap = new Map(
     // prettier-ignore

test/typecheck.js

@@ -750,6 +750,32 @@ describe('typechecking completions', () => {
         </emu-alg>
         </emu-clause>
       `);
+
+      await assertLintFree(`
+        <emu-clause id="example" type="abstract operation">
+        <h1>
+          ExampleAlg (): a mathematical value
+        </h1>
+        <dl class="header">
+          <dt>skip global checks</dt>
+          <dd>true</dd>
+        </dl>
+        <emu-alg>
+          1. Return 0.
+        </emu-alg>
+        </emu-clause>
+
+        <emu-clause id="example2" type="abstract operation">
+        <h1>
+          Example2 ()
+        </h1>
+        <dl class="header">
+        </dl>
+        <emu-alg>
+        1. Perform ExampleAlg().
+        </emu-alg>
+        </emu-clause>
+      `);
     });
   });