Fix strict-type-predicate for unknown (#4444)

* Add tests for strict-type-predicates and unknown

* Fix unknown with strict-type-predicate

* Fix unknown literal

src/rules/strictTypePredicatesRule.ts

@@ -99,7 +99,12 @@ function walk(ctx: Lint.WalkContext<void>, checker: ts.TypeChecker): void {
 
         const exprType = checker.getTypeAtLocation(exprPred.expression);
         // TODO: could use checker.getBaseConstraintOfType to help with type parameters, but it's not publicly exposed.
-        if (isTypeFlagSet(exprType, ts.TypeFlags.Any | ts.TypeFlags.TypeParameter)) {
+        if (
+            isTypeFlagSet(
+                exprType,
+                ts.TypeFlags.Any | ts.TypeFlags.TypeParameter | ts.TypeFlags.Unknown,
+            )
+        ) {
             return;
         }
 

test/rules/strict-type-predicates/strict-null-checks/test.ts.lint

@@ -194,6 +194,9 @@ declare function get<T>(): T;
     typeof get<string | number>() === `stirng`;
     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [typeof]
 
+    typeof get<any>() === "unknown";
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [typeof]
+
     let a: string, b: string;
     typeof a === typeof b;
     typeof a === b;

test/rules/strict-type-predicates/unknown/test.ts.lint

@@ -0,0 +1,42 @@
+[typescript]: >= 3.0.0
+
+declare function get<T>(): T;
+
+// typeof
+{
+    typeof get<unknown>() === "undefined";
+    typeof get<unknown>() === "boolean";
+    typeof get<unknown>() === "number";
+    typeof get<unknown>() === "string";
+    typeof get<unknown>() === "symbol";
+    typeof get<unknown>() === "function";
+    typeof get<unknown>() === "object";
+}
+
+// negation
+{
+    get<unknown>() !== null;
+    get<unknown>() !== undefined;
+}
+
+// reverse left/right
+{
+    "string" === typeof get<unknown>();
+
+    undefined === get<unknown>();
+}
+
+// type parameters
+{
+    function f<T>(t: T) {
+        typeof t === "boolean";
+    }
+}
+
+const body: unknown = 'test';
+if (typeof body === 'object')
+    console.log('a');
+
+let test: unknown = undefined;
+if (test !== undefined)
+    console.log('b');

test/rules/strict-type-predicates/unknown/tsconfig.json

@@ -0,0 +1,5 @@
+{
+    "compilerOptions": {
+        "strictNullChecks": true
+    }
+}

test/rules/strict-type-predicates/unknown/tslint.json

@@ -0,0 +1,5 @@
+{
+  "rules": {
+    "strict-type-predicates": true
+  }
+}