Add codefix for 'convert to unknown' diagnostic

Codefix for diagnostic error 2352: "Conversion of type '{0}' to type '{1}' may be
a mistake because neither type sufficiently overlaps with the other. If this was
intentional, convert the expression to 'unknown' first."

Add codefix for both AsExpressions and TypeAssertions

src/compiler/diagnosticMessages.json

@@ -4724,5 +4724,13 @@
     "Generate types for all packages without types": {
         "category": "Message",
         "code": 95068
+    },
+    "Add 'unknown' conversion for non-overlapping types": {
+        "category": "Message",
+        "code": 95069
+    },
+    "Add 'unknown' to all conversions of non-overlapping types": {
+        "category": "Message",
+        "code": 95070
     }
 }

src/services/codefixes/addConvertToUnknownForNonOverlappingTypes.ts

@@ -0,0 +1,42 @@
+/* @internal */
+namespace ts.codefix {
+    const fixId = "addConvertToUnknownForNonOverlappingTypes";
+    const errorCodes = [Diagnostics.Conversion_of_type_0_to_type_1_may_be_a_mistake_because_neither_type_sufficiently_overlaps_with_the_other_If_this_was_intentional_convert_the_expression_to_unknown_first.code];
+    registerCodeFix({
+        errorCodes,
+        getCodeActions: (context) => {
+            const changes = textChanges.ChangeTracker.with(context, t => makeChange(t, context.sourceFile, context.span.start));
+            return [createCodeFixAction(fixId, changes, Diagnostics.Add_unknown_conversion_for_non_overlapping_types, fixId, Diagnostics.Add_unknown_to_all_conversions_of_non_overlapping_types)];
+        },
+        fixIds: [fixId],
+        getAllCodeActions: context => codeFixAll(context, errorCodes, (changes, diag) => makeChange(changes, diag.file, diag.start)),
+    });
+
+    function makeChange(changeTracker: textChanges.ChangeTracker, sourceFile: SourceFile, pos: number) {
+        const token = getTokenAtPosition(sourceFile, pos);
+
+        const asExpression = findAncestor<AsExpression>(token, isAsExpression)!;
+        if (!!asExpression) {
+            Debug.assert(!!asExpression, "Expected position to be owned by an as-expression.");
+
+            const nodeBeingCast = asExpression.getChildAt(0);
+            const expressionBeingCast = findAncestor<Expression>(nodeBeingCast, isExpression)!;
+            Debug.assert(!!expressionBeingCast, "Expected position to be owned by an expression.");
+
+            const replacement = createAsExpression(expressionBeingCast, createKeywordTypeNode(SyntaxKind.UnknownKeyword));
+            changeTracker.replaceNode(sourceFile, expressionBeingCast, replacement);
+        }
+
+        const typeAssertion = findAncestor<TypeAssertion>(token, isTypeAssertion)!;
+        if (!!typeAssertion) {
+            Debug.assert(!!typeAssertion, "Expected position to be owned by a type assertion.");
+
+            const nodeBeingCast = typeAssertion.getLastToken();
+            const expressionBeingCast = findAncestor<Expression>(nodeBeingCast, isExpression)!;
+            Debug.assert(!!expressionBeingCast, "Expected position to be owned by an expression.");
+
+            const replacement = createTypeAssertion(createKeywordTypeNode(SyntaxKind.UnknownKeyword), expressionBeingCast);
+            changeTracker.replaceNode(sourceFile, expressionBeingCast, replacement);
+        }
+    }
+}

src/services/tsconfig.json

@@ -43,6 +43,7 @@
         "textChanges.ts",
         "codeFixProvider.ts",
         "refactorProvider.ts",
+        "codefixes/addConvertToUnknownForNonOverlappingTypes.ts",
         "codefixes/addMissingInvocationForDecorator.ts",
         "codefixes/annotateWithTypeFromJSDoc.ts",
         "codefixes/convertFunctionToEs6Class.ts",

tests/cases/fourslash/codeFixAddConvertToUnknownForNonOverlappingTypes1.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+////[|0 as string|]
+
+verify.codeFix({
+    description: "Add 'unknown' conversion for non-overlapping types",
+    newRangeContent: `0 as unknown as string`
+});

tests/cases/fourslash/codeFixAddConvertToUnknownForNonOverlappingTypes2.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+////[|0 * (4 + 3) / 100 as string|]
+
+verify.codeFix({
+    description: "Add 'unknown' conversion for non-overlapping types",
+    newRangeContent: `0 * (4 + 3) / 100 as unknown as string`
+});

tests/cases/fourslash/codeFixAddConvertToUnknownForNonOverlappingTypes3.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+////[|["words"] as string|]
+
+verify.codeFix({
+    description: "Add 'unknown' conversion for non-overlapping types",
+    newRangeContent: `["words"] as unknown as string`
+});

tests/cases/fourslash/codeFixAddConvertToUnknownForNonOverlappingTypes4.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+////[|"words" as object|]
+
+verify.codeFix({
+    description: "Add 'unknown' conversion for non-overlapping types",
+    newRangeContent: `"words" as unknown as object`
+});

tests/cases/fourslash/codeFixAddConvertToUnknownForNonOverlappingTypes5.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+////[|<string>0|]
+
+verify.codeFix({
+    description: "Add 'unknown' conversion for non-overlapping types",
+    newRangeContent: `<string><unknown>0`
+});

tests/cases/fourslash/codeFixAddConvertToUnknownForNonOverlappingTypes6.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+////[|<string>0 * (4 + 3) / 100|]
+
+verify.codeFix({
+    description: "Add 'unknown' conversion for non-overlapping types",
+    newRangeContent: `<string><unknown>0 * (4 + 3) / 100`
+});

tests/cases/fourslash/codeFixAddConvertToUnknownForNonOverlappingTypes7.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+////[|<string>["words"]|]
+
+verify.codeFix({
+    description: "Add 'unknown' conversion for non-overlapping types",
+    newRangeContent: `<string><unknown>["words"]`
+});

tests/cases/fourslash/codeFixAddConvertToUnknownForNonOverlappingTypes8.ts

@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+////[|<object>"words"|]
+
+verify.codeFix({
+    description: "Add 'unknown' conversion for non-overlapping types",
+    newRangeContent: `<object><unknown>"words"`
+});

tests/cases/fourslash/codeFixAddConvertToUnknownForNonOverlappingTypes_all.ts

@@ -0,0 +1,22 @@
+/// <reference path='fourslash.ts' />
+
+////class C {
+////    const s1 = 1 as string;
+////    const o1 = s + " word" as object;
+////
+////    const s2 = <string>2;
+////    const o2 = <object>s2;
+////}
+
+verify.codeFixAll({
+    fixId: "addConvertToUnknownForNonOverlappingTypes",
+    fixAllDescription: "Add 'unknown' to all conversions of non-overlapping types",
+    newFileContent:
+`class C {
+    const s1 = 1 as unknown as string;
+    const o1 = s + " word" as unknown as object;
+
+    const s2 = <string><unknown>2;
+    const o2 = <object>s2;
+}`
+});