feat(eslint-plugin): [restrict-plus-operands] add intersection type d…

…etermination logic (#2628)
typescript-eslint · Oct 18, 2020 · da71362 · da71362
1 parent bbc9e35
commit da71362
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diff --git a/packages/eslint-plugin/src/rules/restrict-plus-operands.ts b/packages/eslint-plugin/src/rules/restrict-plus-operands.ts
@@ -70,6 +70,11 @@ export default util.createRule<Options, MessageIds>({
         return types.every(value => value === types[0]) ? types[0] : 'invalid';
       }
 
+      if (type.isIntersection()) {
+        const types = type.types.map(getBaseTypeOfLiteralType);
+        return types.some(value => value === 'string') ? 'string' : 'invalid';
+      }
+
       const stringType = typeChecker.typeToString(type);
 
       if (

diff --git a/packages/eslint-plugin/tests/rules/restrict-plus-operands.test.ts b/packages/eslint-plugin/tests/rules/restrict-plus-operands.test.ts
@@ -90,6 +90,26 @@ function foo<T extends number>(a: T) {
 function foo<T extends 1>(a: T) {
   return a + 1;
 }
+    `,
+    `
+declare const a: {} & string;
+declare const b: string;
+const x = a + b;
+    `,
+    `
+declare const a: unknown & string;
+declare const b: string;
+const x = a + b;
+    `,
+    `
+declare const a: string & string;
+declare const b: string;
+const x = a + b;
+    `,
+    `
+declare const a: 'string literal' & string;
+declare const b: string;
+const x = a + b;
     `,
     {
       code: `
@@ -411,6 +431,104 @@ function foo<T extends 1>(a: T) {
         },
       ],
     },
+    {
+      code: `
+        declare const a: boolean & string;
+        declare const b: string;
+        const x = a + b;
+      `,
+      errors: [
+        {
+          messageId: 'notStrings',
+          line: 4,
+          column: 19,
+        },
+      ],
+    },
+    {
+      code: `
+        declare const a: number & string;
+        declare const b: string;
+        const x = a + b;
+      `,
+      errors: [
+        {
+          messageId: 'notStrings',
+          line: 4,
+          column: 19,
+        },
+      ],
+    },
+    {
+      code: `
+        declare const a: symbol & string;
+        declare const b: string;
+        const x = a + b;
+      `,
+      errors: [
+        {
+          messageId: 'notStrings',
+          line: 4,
+          column: 19,
+        },
+      ],
+    },
+    {
+      code: `
+        declare const a: object & string;
+        declare const b: string;
+        const x = a + b;
+      `,
+      errors: [
+        {
+          messageId: 'notStrings',
+          line: 4,
+          column: 19,
+        },
+      ],
+    },
+    {
+      code: `
+        declare const a: never & string;
+        declare const b: string;
+        const x = a + b;
+      `,
+      errors: [
+        {
+          messageId: 'notStrings',
+          line: 4,
+          column: 19,
+        },
+      ],
+    },
+    {
+      code: `
+        declare const a: any & string;
+        declare const b: string;
+        const x = a + b;
+      `,
+      errors: [
+        {
+          messageId: 'notStrings',
+          line: 4,
+          column: 19,
+        },
+      ],
+    },
+    {
+      code: `
+        declare const a: { a: 1 } & { b: 2 };
+        declare const b: string;
+        const x = a + b;
+      `,
+      errors: [
+        {
+          messageId: 'notStrings',
+          line: 4,
+          column: 19,
+        },
+      ],
+    },
     {
       code: `
 let foo: string | undefined;