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diff --git a/‎src/compiler/checker.ts
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+3Lines changed: 3 additions & 0 deletions b/‎src/compiler/checker.ts
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diff --git a/‎src/compiler/commandLineParser.ts
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+9Lines changed: 9 additions & 0 deletions b/‎src/compiler/commandLineParser.ts
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diff --git a/‎src/compiler/diagnosticMessages.json
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+17-1Lines changed: 17 additions & 1 deletion b/‎src/compiler/diagnosticMessages.json
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+17-1Lines changed: 17 additions & 1 deletion
diff --git a/‎src/compiler/types.ts
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+1Lines changed: 1 addition & 0 deletions b/‎src/compiler/types.ts
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diff --git a/‎src/services/codefixes/fixNoPropertyAccessFromIndexSignature.ts
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+35Lines changed: 35 additions & 0 deletions b/‎src/services/codefixes/fixNoPropertyAccessFromIndexSignature.ts
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diff --git a/‎src/services/tsconfig.json
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+1Lines changed: 1 addition & 0 deletions b/‎src/services/tsconfig.json
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diff --git a/‎tests/baselines/reference/api/tsserverlibrary.d.ts
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+1Lines changed: 1 addition & 0 deletions b/‎tests/baselines/reference/api/tsserverlibrary.d.ts
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diff --git a/‎tests/baselines/reference/api/typescript.d.ts
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+1Lines changed: 1 addition & 0 deletions b/‎tests/baselines/reference/api/typescript.d.ts
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diff --git a/‎tests/baselines/reference/noPropertyAccessFromIndexSignature1.errors.txt
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+54Lines changed: 54 additions & 0 deletions b/‎tests/baselines/reference/noPropertyAccessFromIndexSignature1.errors.txt
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diff --git a/‎tests/baselines/reference/noPropertyAccessFromIndexSignature1.js
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+63Lines changed: 63 additions & 0 deletions b/‎tests/baselines/reference/noPropertyAccessFromIndexSignature1.js
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+63Lines changed: 63 additions & 0 deletions
@@ -25865,6 +25865,9 @@ namespace ts {
                 }
 
                 propType = (compilerOptions.noUncheckedIndexedAccess && !isAssignmentTarget(node)) ? getUnionType([indexInfo.type, undefinedType]) : indexInfo.type;
+                if (compilerOptions.noPropertyAccessFromIndexSignature && isPropertyAccessExpression(node)) {
+                    error(node, Diagnostics.Property_0_comes_from_an_index_signature_so_it_must_be_accessed_with_0, unescapeLeadingUnderscores(right.escapedText));
+                }
             }
             else {
                 if (getDeclarationNodeFlagsFromSymbol(prop) & NodeFlags.Deprecated && isUncalledFunctionReference(node, prop)) {
 
@@ -635,6 +635,15 @@ namespace ts {
             category: Diagnostics.Additional_Checks,
             description: Diagnostics.Include_undefined_in_index_signature_results
         },
+        {
+            name: "noPropertyAccessFromIndexSignature",
+            type: "boolean",
+            affectsBindDiagnostics: true,
+            affectsSemanticDiagnostics: true,
+            showInSimplifiedHelpView: false,
+            category: Diagnostics.Additional_Checks,
+            description: Diagnostics.Require_undeclared_properties_from_index_signatures_to_use_element_accesses
+        },
 
         // Module Resolution
         {
 
@@ -3428,6 +3428,10 @@
         "category": "Error",
         "code": 4110
     },
+    "Property '{0}' comes from an index signature, so it must be accessed with ['{0}'].": {
+        "category": "Error",
+        "code": 4111
+    },
 
     "The current host does not support the '{0}' option.": {
         "category": "Error",
@@ -4744,6 +4748,10 @@
         "category": "Error",
         "code": 6504
     },
+    "Require undeclared properties from index signatures to use element accesses.": {
+        "category": "Error",
+        "code": 6803
+    },
 
     "Include 'undefined' in index signature results": {
         "category": "Message",
@@ -5959,10 +5967,18 @@
         "category": "Message",
         "code": 95144
     },
-    "Delete all unused imports": {
+    "Use element access for '{0}'": {
         "category": "Message",
         "code": 95145
     },
+    "Use element access for all undeclared properties.": {
+        "category": "Message",
+        "code": 95146
+    },
+    "Delete all unused imports": {
+        "category": "Message",
+        "code": 95147
+    },
 
     "No value exists in scope for the shorthand property '{0}'. Either declare one or provide an initializer.": {
         "category": "Error",
 
@@ -5784,6 +5784,7 @@ namespace ts {
         noUnusedLocals?: boolean;
         noUnusedParameters?: boolean;
         noImplicitUseStrict?: boolean;
+        noPropertyAccessFromIndexSignature?: boolean;
         assumeChangesOnlyAffectDirectDependencies?: boolean;
         noLib?: boolean;
         noResolve?: boolean;
 
@@ -0,0 +1,35 @@
+/* @internal */
+namespace ts.codefix {
+    const fixId = "fixNoPropertyAccessFromIndexSignature";
+    const errorCodes = [
+        Diagnostics.Property_0_comes_from_an_index_signature_so_it_must_be_accessed_with_0.code
+    ];
+
+    registerCodeFix({
+        errorCodes,
+        fixIds: [fixId],
+        getCodeActions(context) {
+            const { sourceFile, span } = context;
+            const property = getPropertyAccessExpression(sourceFile, span.start);
+            const changes = textChanges.ChangeTracker.with(context, t => doChange(t, context.sourceFile, property));
+            return [createCodeFixAction(fixId, changes, [Diagnostics.Use_element_access_for_0, property.name.text], fixId, Diagnostics.Use_element_access_for_all_undeclared_properties)];
+        },
+        getAllCodeActions: context =>
+            codeFixAll(context, errorCodes, (changes, diag) => doChange(changes, diag.file, getPropertyAccessExpression(diag.file, diag.start)))
+    });
+
+    function doChange(changes: textChanges.ChangeTracker, sourceFile: SourceFile, node: PropertyAccessExpression): void {
+        const argumentsExpression = factory.createStringLiteral(node.name.text);
+        changes.replaceNode(
+            sourceFile,
+            node,
+            isPropertyAccessChain(node) ?
+                factory.createElementAccessChain(node.expression, node.questionDotToken, argumentsExpression) :
+                factory.createElementAccessExpression(node.expression, argumentsExpression)
+        );
+    }
+
+    function getPropertyAccessExpression(sourceFile: SourceFile, pos: number): PropertyAccessExpression {
+        return cast(getTokenAtPosition(sourceFile, pos).parent, isPropertyAccessExpression);
+    }
+}
@@ -65,6 +65,7 @@
         "codefixes/convertLiteralTypeToMappedType.ts",
         "codefixes/fixClassIncorrectlyImplementsInterface.ts",
         "codefixes/importFixes.ts",
+        "codefixes/fixNoPropertyAccessFromIndexSignature.ts",
         "codefixes/fixImplicitThis.ts",
         "codefixes/fixIncorrectNamedTupleSyntax.ts",
         "codefixes/fixSpelling.ts",
 
@@ -2832,6 +2832,7 @@ declare namespace ts {
         noUnusedLocals?: boolean;
         noUnusedParameters?: boolean;
         noImplicitUseStrict?: boolean;
+        noPropertyAccessFromIndexSignature?: boolean;
         assumeChangesOnlyAffectDirectDependencies?: boolean;
         noLib?: boolean;
         noResolve?: boolean;
 
@@ -2832,6 +2832,7 @@ declare namespace ts {
         noUnusedLocals?: boolean;
         noUnusedParameters?: boolean;
         noImplicitUseStrict?: boolean;
+        noPropertyAccessFromIndexSignature?: boolean;
         assumeChangesOnlyAffectDirectDependencies?: boolean;
         noLib?: boolean;
         noResolve?: boolean;
 
@@ -0,0 +1,54 @@
+tests/cases/conformance/additionalChecks/noPropertyAccessFromIndexSignature1.ts(24,1): error TS4111: Property 'foo' comes from an index signature, so it must be accessed with ['foo'].
+tests/cases/conformance/additionalChecks/noPropertyAccessFromIndexSignature1.ts(32,1): error TS4111: Property 'bar' comes from an index signature, so it must be accessed with ['bar'].
+tests/cases/conformance/additionalChecks/noPropertyAccessFromIndexSignature1.ts(40,1): error TS4111: Property 'bar' comes from an index signature, so it must be accessed with ['bar'].
+
+
+==== tests/cases/conformance/additionalChecks/noPropertyAccessFromIndexSignature1.ts (3 errors) ====
+    interface A {
+        foo: string
+    }
+    
+    interface B {
+        [k: string]: string
+    }
+    
+    interface C {
+        foo: string
+        [k: string]: string
+    }
+    
+    declare const a: A;
+    declare const b: B;
+    declare const c: C;
+    declare const d: C | undefined;
+    
+    // access property
+    a.foo;
+    a["foo"]
+    
+    // access index signature
+    b.foo;
+    ~~~~~
+!!! error TS4111: Property 'foo' comes from an index signature, so it must be accessed with ['foo'].
+    b["foo"];
+    
+    // access property
+    c.foo;
+    c["foo"]
+    
+    // access index signature
+    c.bar;
+    ~~~~~
+!!! error TS4111: Property 'bar' comes from an index signature, so it must be accessed with ['bar'].
+    c["bar"];
+    
+    // optional access property
+    d?.foo;
+    d?.["foo"]
+    
+    // optional access index signature
+    d?.bar;
+    ~~~~~~
+!!! error TS4111: Property 'bar' comes from an index signature, so it must be accessed with ['bar'].
+    d?.["bar"];
+    
@@ -0,0 +1,63 @@
+//// [noPropertyAccessFromIndexSignature1.ts]
+interface A {
+    foo: string
+}
+
+interface B {
+    [k: string]: string
+}
+
+interface C {
+    foo: string
+    [k: string]: string
+}
+
+declare const a: A;
+declare const b: B;
+declare const c: C;
+declare const d: C | undefined;
+
+// access property
+a.foo;
+a["foo"]
+
+// access index signature
+b.foo;
+b["foo"];
+
+// access property
+c.foo;
+c["foo"]
+
+// access index signature
+c.bar;
+c["bar"];
+
+// optional access property
+d?.foo;
+d?.["foo"]
+
+// optional access index signature
+d?.bar;
+d?.["bar"];
+
+
+//// [noPropertyAccessFromIndexSignature1.js]
+// access property
+a.foo;
+a["foo"];
+// access index signature
+b.foo;
+b["foo"];
+// access property
+c.foo;
+c["foo"];
+// access index signature
+c.bar;
+c["bar"];
+// optional access property
+d === null || d === void 0 ? void 0 : d.foo;
+d === null || d === void 0 ? void 0 : d["foo"];
+// optional access index signature
+d === null || d === void 0 ? void 0 : d.bar;
+d === null || d === void 0 ? void 0 : d["bar"];
Original file line number	Diff line number	Diff line change
`@@ -25865,6 +25865,9 @@ namespace ts {`
`25865`	`25865`	`}`
`25866`	`25866`
`25867`	`25867`	`propType = (compilerOptions.noUncheckedIndexedAccess && !isAssignmentTarget(node)) ? getUnionType([indexInfo.type, undefinedType]) : indexInfo.type;`
	`25868`	`+ if (compilerOptions.noPropertyAccessFromIndexSignature && isPropertyAccessExpression(node)) {`
	`25869`	`+ error(node, Diagnostics.Property_0_comes_from_an_index_signature_so_it_must_be_accessed_with_0, unescapeLeadingUnderscores(right.escapedText));`
	`25870`	`+ }`
`25868`	`25871`	`}`
`25869`	`25872`	`else {`
`25870`	`25873`	`if (getDeclarationNodeFlagsFromSymbol(prop) & NodeFlags.Deprecated && isUncalledFunctionReference(node, prop)) {`