feat(eslint-plugin): [no-unnecessary-type-assertion] use getContextua…

…lType directly
typescript-eslint · Mar 2, 2021 · 97e184c · 97e184c
1 parent 3e204e9
commit 97e184c
Show file tree

Hide file tree

Showing 2 changed files with 73 additions and 33 deletions.
diff --git a/packages/eslint-plugin/src/util/types.ts b/packages/eslint-plugin/src/util/types.ts
@@ -1,16 +1,8 @@
 import debug from 'debug';
 import {
-  isCallExpression,
-  isJsxExpression,
-  isIdentifier,
-  isNewExpression,
-  isParameterDeclaration,
-  isPropertyDeclaration,
   isTypeReference,
   isUnionOrIntersectionType,
-  isVariableDeclaration,
   unionTypeParts,
-  isPropertyAssignment,
 } from 'tsutils';
 import * as ts from 'typescript';
 
@@ -483,30 +475,5 @@ export function getContextualType(
     return;
   }
 
-  if (isCallExpression(parent) || isNewExpression(parent)) {
-    if (node === parent.expression) {
-      // is the callee, so has no contextual type
-      return;
-    }
-  } else if (
-    isVariableDeclaration(parent) ||
-    isPropertyDeclaration(parent) ||
-    isParameterDeclaration(parent)
-  ) {
-    return parent.type ? checker.getTypeFromTypeNode(parent.type) : undefined;
-  } else if (isJsxExpression(parent)) {
-    return checker.getContextualType(parent);
-  } else if (isPropertyAssignment(parent) && isIdentifier(node)) {
-    return checker.getContextualType(node);
-  } else if (
-    ![ts.SyntaxKind.TemplateSpan, ts.SyntaxKind.JsxExpression].includes(
-      parent.kind,
-    )
-  ) {
-    // parent is not something we know we can get the contextual type of
-    return;
-  }
-  // TODO - support return statement checking
-
   return checker.getContextualType(node);
 }
diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
@@ -186,6 +186,41 @@ const c = <const>[...a, ...b];
     {
       code: "const a = <const>{ foo: 'foo' };",
     },
+    {
+      code: `
+let a: number | undefined;
+let b: number | undefined;
+a = b;
+a != b;
+a == !b;
+a! != b!;
+a! != b;
+      `,
+    },
+    {
+      code: `
+function num(): number {
+  let n: number | undefined;
+  return n!;
+}
+      `,
+    },
+    {
+      code: `
+function num() {
+  let n: number | undefined;
+  return n!;
+}
+      `,
+    },
+    {
+      code: `
+async function num(): Promise<number> {
+  let n: Promise<number> | undefined;
+  return n!;
+}
+      `,
+    },
   ],
 
   invalid: [
@@ -451,5 +486,43 @@ function Test(props: { id?: string | number }) {
       ],
       filename: 'react.tsx',
     },
+    {
+      code: `
+let x: number | undefined;
+let y: number | undefined;
+y = x!;
+      `,
+      output: `
+let x: number | undefined;
+let y: number | undefined;
+y = x;
+      `,
+      errors: [
+        {
+          messageId: 'contextuallyUnnecessary',
+          line: 4,
+        },
+      ],
+    },
+    {
+      code: `
+function num(): number | undefined {
+  let n: number | undefined;
+  return n!;
+}
+      `,
+      output: `
+function num(): number | undefined {
+  let n: number | undefined;
+  return n;
+}
+      `,
+      errors: [
+        {
+          messageId: 'contextuallyUnnecessary',
+          line: 4,
+        },
+      ],
+    },
   ],
 });