Issue "Cannot find name did-you-mean" errors as suggestions in plain JS (#44271)

* Always issue cannot find name did-you-mean error

This PR issues "cannot find ${name}, did you mean ${name}" errors for
identifiers and propery access expressions in JS files *without*
`// @ts-check` and without `// @ts-nocheck`. This brings some benefits of
Typescript's binder to all Javascript users, even those who haven't
opted into Typescript checking.

```js
export var inModule = 1
inmodule.toFixed() // errors on exports

function f() {
    var locals = 2
    locale.toFixed() // errors on locals
}
var object = {
    spaaace: 3
}
object.spaaaace // error on read
object.spaace = 2 // error on write
object.fresh = 12 // OK, no spelling correction to offer
```

To disable the errors, add `// @ts-nocheck` to the file. To get the
normal checkJs experience, add `// @ts-check`.

== Why This Works ==

In a word: precision. This change has low recall — it misses lots
of correct errors that would be nice to show — but it has high
precision: almost all the errors it shows are correct. And they come
with a suggested correction.

Here are the ingredients:

1. For unchecked JS files, the compiler suppresses all errors except
two did-you-mean name resolution errors.
2. Did-you-mean spelling correction is already tuned for high
precision/low recall, and doesn't show many bogus errors even in JS.
3. For identifiers, the error is suppressed for suggestions from global files.
These are often DOM feature detection, for example.
4. For property accesses, the error is suppressed for suggestions from
other files, for the same reason.
5. For property accesses, the error is suppressed for `this` property
accesses because the compiler doesn't understand JS constructor
functions well enough.
In particular, it doesn't understand any inheritance patterns.

== Work Remaining ==

1. Code cleanup.
2. Fix a couple of failures in existing tests.
3. Suppress errors on property access suggestions from large objects.
4. Combine (3) and (4) above to suppress errors on suggestions from other, global files.
5. A little more testing on random files to make sure that precision
is good there too.
6. Have people from the regular Code editor meeting test the code and
suggest ideas.

* all (most?) tests pass

* NOW they all pass

* add tonnes of semi-colons

* restore this.x check+add a test case

* make ts-ignore/no-check codefix work in unchecked js

* Issues errors only in the language service

* add a few more tests

* fix incorrect parentheses

* More cleanup in program.ts

* Improve readability of isExcludedJSError

* make diff in program.ts smaller via closure

* Switch unchecked JS did-you-mean to suggestion

Instead of selectively letting errors through.

* undo more missed changes

* disallow ignoring suggestions

* Issue different messages for plain JS than others

Straw text for the messages, I just changed the modals to avoid name
collisions.

src/compiler/builder.ts

@@ -683,7 +683,7 @@ namespace ts {
             const cachedDiagnostics = state.semanticDiagnosticsPerFile.get(path);
             // Report the bind and check diagnostics from the cache if we already have those diagnostics present
             if (cachedDiagnostics) {
-                return filterSemanticDiagnotics(cachedDiagnostics, state.compilerOptions);
+                return filterSemanticDiagnostics(cachedDiagnostics, state.compilerOptions);
             }
         }
 
@@ -692,7 +692,7 @@ namespace ts {
         if (state.semanticDiagnosticsPerFile) {
             state.semanticDiagnosticsPerFile.set(path, diagnostics);
         }
-        return filterSemanticDiagnotics(diagnostics, state.compilerOptions);
+        return filterSemanticDiagnostics(diagnostics, state.compilerOptions);
     }
 
     export type ProgramBuildInfoFileId = number & { __programBuildInfoFileIdBrand: any };

src/compiler/checker.ts

@@ -1072,15 +1072,19 @@ namespace ts {
             return diagnostic;
         }
 
-        function error(location: Node | undefined, message: DiagnosticMessage, arg0?: string | number, arg1?: string | number, arg2?: string | number, arg3?: string | number): Diagnostic {
-            const diagnostic = location
+        function createError(location: Node | undefined, message: DiagnosticMessage, arg0?: string | number, arg1?: string | number, arg2?: string | number, arg3?: string | number): Diagnostic {
+            return location
                 ? createDiagnosticForNode(location, message, arg0, arg1, arg2, arg3)
                 : createCompilerDiagnostic(message, arg0, arg1, arg2, arg3);
+        }
+
+        function error(location: Node | undefined, message: DiagnosticMessage, arg0?: string | number, arg1?: string | number, arg2?: string | number, arg3?: string | number): Diagnostic {
+            const diagnostic = createError(location, message, arg0, arg1, arg2, arg3);
             diagnostics.add(diagnostic);
             return diagnostic;
         }
 
-        function addErrorOrSuggestion(isError: boolean, diagnostic: DiagnosticWithLocation) {
+        function addErrorOrSuggestion(isError: boolean, diagnostic: Diagnostic) {
             if (isError) {
                 diagnostics.add(diagnostic);
             }
@@ -1704,8 +1708,8 @@ namespace ts {
             nameArg: __String | Identifier | undefined,
             isUse: boolean,
             excludeGlobals = false,
-            suggestedNameNotFoundMessage?: DiagnosticMessage): Symbol | undefined {
-            return resolveNameHelper(location, name, meaning, nameNotFoundMessage, nameArg, isUse, excludeGlobals, getSymbol, suggestedNameNotFoundMessage);
+            issueSuggestions?: boolean): Symbol | undefined {
+            return resolveNameHelper(location, name, meaning, nameNotFoundMessage, nameArg, isUse, excludeGlobals, getSymbol, issueSuggestions);
         }
 
         function resolveNameHelper(
@@ -1716,8 +1720,7 @@ namespace ts {
             nameArg: __String | Identifier | undefined,
             isUse: boolean,
             excludeGlobals: boolean,
-            lookup: typeof getSymbol,
-            suggestedNameNotFoundMessage?: DiagnosticMessage): Symbol | undefined {
+            lookup: typeof getSymbol, issueSuggestions?: boolean): Symbol | undefined {
             const originalLocation = location; // needed for did-you-mean error reporting, which gathers candidates starting from the original location
             let result: Symbol | undefined;
             let lastLocation: Node | undefined;
@@ -2054,15 +2057,19 @@ namespace ts {
                         !checkAndReportErrorForUsingNamespaceModuleAsValue(errorLocation, name, meaning) &&
                         !checkAndReportErrorForUsingValueAsType(errorLocation, name, meaning)) {
                         let suggestion: Symbol | undefined;
-                        if (suggestedNameNotFoundMessage && suggestionCount < maximumSuggestionCount) {
+                        if (issueSuggestions && suggestionCount < maximumSuggestionCount) {
                             suggestion = getSuggestedSymbolForNonexistentSymbol(originalLocation, name, meaning);
-                            const isGlobalScopeAugmentationDeclaration = suggestion && suggestion.valueDeclaration && isAmbientModule(suggestion.valueDeclaration) && isGlobalScopeAugmentation(suggestion.valueDeclaration);
+                            const isGlobalScopeAugmentationDeclaration = suggestion?.valueDeclaration && isAmbientModule(suggestion.valueDeclaration) && isGlobalScopeAugmentation(suggestion.valueDeclaration);
                             if (isGlobalScopeAugmentationDeclaration) {
                                 suggestion = undefined;
                             }
                             if (suggestion) {
                                 const suggestionName = symbolToString(suggestion);
-                                const diagnostic = error(errorLocation, suggestedNameNotFoundMessage, diagnosticName(nameArg!), suggestionName);
+                                const isUncheckedJS = isUncheckedJSSuggestion(originalLocation, suggestion, /*excludeClasses*/ false);
+                                const message = isUncheckedJS ? Diagnostics.Could_not_find_name_0_Did_you_mean_1 : Diagnostics.Cannot_find_name_0_Did_you_mean_1;
+                                const diagnostic = createError(errorLocation, message, diagnosticName(nameArg!), suggestionName);
+                                addErrorOrSuggestion(!isUncheckedJS, diagnostic);
+
                                 if (suggestion.valueDeclaration) {
                                     addRelatedInfo(
                                         diagnostic,
@@ -21923,7 +21930,7 @@ namespace ts {
                         node,
                         !isWriteOnlyAccess(node),
                         /*excludeGlobals*/ false,
-                        Diagnostics.Cannot_find_name_0_Did_you_mean_1) || unknownSymbol;
+                        /*issueSuggestions*/ true) || unknownSymbol;
             }
             return links.resolvedSymbol;
         }
@@ -27437,7 +27444,8 @@ namespace ts {
             if (!prop) {
                 const indexInfo = !isPrivateIdentifier(right) && (assignmentKind === AssignmentKind.None || !isGenericObjectType(leftType) || isThisTypeParameter(leftType)) ? getIndexInfoOfType(apparentType, IndexKind.String) : undefined;
                 if (!(indexInfo && indexInfo.type)) {
-                    if (isJSLiteralType(leftType)) {
+                    const isUncheckedJS = isUncheckedJSSuggestion(node, leftType.symbol, /*excludeClasses*/ true);
+                    if (!isUncheckedJS && isJSLiteralType(leftType)) {
                         return anyType;
                     }
                     if (leftType.symbol === globalThisSymbol) {
@@ -27450,7 +27458,7 @@ namespace ts {
                         return anyType;
                     }
                     if (right.escapedText && !checkAndReportErrorForExtendingInterface(node)) {
-                        reportNonexistentProperty(right, isThisTypeParameter(leftType) ? apparentType : leftType);
+                        reportNonexistentProperty(right, isThisTypeParameter(leftType) ? apparentType : leftType, isUncheckedJS);
                     }
                     return errorType;
                 }
@@ -27483,6 +27491,26 @@ namespace ts {
             return getFlowTypeOfAccessExpression(node, prop, propType, right, checkMode);
         }
 
+        /**
+         * Determines whether a did-you-mean error should be a suggestion in an unchecked JS file.
+         * Only applies to unchecked JS files without checkJS, // @ts-check or // @ts-nocheck
+         * It does not suggest when the suggestion:
+         * - Is from a global file that is different from the reference file, or
+         * - (optionally) Is a class, or is a this.x property access expression
+         */
+        function isUncheckedJSSuggestion(node: Node | undefined, suggestion: Symbol | undefined, excludeClasses: boolean): boolean {
+            const file = getSourceFileOfNode(node);
+            if (file) {
+                if (compilerOptions.checkJs === undefined && file.checkJsDirective === undefined && (file.scriptKind === ScriptKind.JS || file.scriptKind === ScriptKind.JSX)) {
+                    const declarationFile = forEach(suggestion?.declarations, getSourceFileOfNode);
+                    return !(file !== declarationFile && !!declarationFile && isGlobalSourceFile(declarationFile))
+                        && !(excludeClasses && suggestion && suggestion.flags & SymbolFlags.Class)
+                        && !(!!node && excludeClasses && isPropertyAccessExpression(node) && node.expression.kind === SyntaxKind.ThisKeyword);
+                }
+            }
+            return false;
+        }
+
         function getFlowTypeOfAccessExpression(node: ElementAccessExpression | PropertyAccessExpression | QualifiedName, prop: Symbol | undefined, propType: Type, errorNode: Node, checkMode: CheckMode | undefined) {
             // Only compute control flow type if this is a property access expression that isn't an
             // assignment target, and the referenced property was declared as a variable, property,
@@ -27614,7 +27642,7 @@ namespace ts {
             return getIntersectionType(x);
         }
 
-        function reportNonexistentProperty(propNode: Identifier | PrivateIdentifier, containingType: Type) {
+        function reportNonexistentProperty(propNode: Identifier | PrivateIdentifier, containingType: Type, isUncheckedJS: boolean) {
             let errorInfo: DiagnosticMessageChain | undefined;
             let relatedInfo: Diagnostic | undefined;
             if (!isPrivateIdentifier(propNode) && containingType.flags & TypeFlags.Union && !(containingType.flags & TypeFlags.Primitive)) {
@@ -27647,7 +27675,8 @@ namespace ts {
                         const suggestion = getSuggestedSymbolForNonexistentProperty(propNode, containingType);
                         if (suggestion !== undefined) {
                             const suggestedName = symbolName(suggestion);
-                            errorInfo = chainDiagnosticMessages(errorInfo, Diagnostics.Property_0_does_not_exist_on_type_1_Did_you_mean_2, missingProperty, container, suggestedName);
+                            const message = isUncheckedJS ? Diagnostics.Property_0_may_not_exist_on_type_1_Did_you_mean_2 : Diagnostics.Property_0_does_not_exist_on_type_1_Did_you_mean_2;
+                            errorInfo = chainDiagnosticMessages(errorInfo, message, missingProperty, container, suggestedName);
                             relatedInfo = suggestion.valueDeclaration && createDiagnosticForNode(suggestion.valueDeclaration, Diagnostics._0_is_declared_here, suggestedName);
                         }
                         else {
@@ -27663,7 +27692,7 @@ namespace ts {
             if (relatedInfo) {
                 addRelatedInfo(resultDiagnostic, relatedInfo);
             }
-            diagnostics.add(resultDiagnostic);
+            addErrorOrSuggestion(!isUncheckedJS, resultDiagnostic);
         }
 
         function containerSeemsToBeEmptyDomElement(containingType: Type) {
@@ -34582,7 +34611,7 @@ namespace ts {
 
             const rootName = getFirstIdentifier(typeName);
             const meaning = (typeName.kind === SyntaxKind.Identifier ? SymbolFlags.Type : SymbolFlags.Namespace) | SymbolFlags.Alias;
-            const rootSymbol = resolveName(rootName, rootName.escapedText, meaning, /*nameNotFoundMessage*/ undefined, /*nameArg*/ undefined, /*isRefernce*/ true);
+            const rootSymbol = resolveName(rootName, rootName.escapedText, meaning, /*nameNotFoundMessage*/ undefined, /*nameArg*/ undefined, /*isReference*/ true);
             if (rootSymbol
                 && rootSymbol.flags & SymbolFlags.Alias
                 && symbolIsValue(rootSymbol)

src/compiler/diagnosticMessages.json

@@ -2442,10 +2442,18 @@
         "category": "Error",
         "code": 2567
     },
+    "Property '{0}' may not exist on type '{1}'. Did you mean '{2}'?": {
+        "category": "Error",
+        "code": 2568
+    },
     "Type '{0}' is not an array type or a string type. Use compiler option '--downlevelIteration' to allow iterating of iterators.": {
         "category": "Error",
         "code": 2569
     },
+    "Could not find name '{0}'. Did you mean '{1}'?": {
+        "category": "Error",
+        "code": 2570
+    },
     "Object is of type 'unknown'.": {
         "category": "Error",
         "code": 2571

src/compiler/program.ts

@@ -1896,7 +1896,7 @@ namespace ts {
 
         function getSemanticDiagnosticsForFile(sourceFile: SourceFile, cancellationToken: CancellationToken | undefined): readonly Diagnostic[] {
             return concatenate(
-                filterSemanticDiagnotics(getBindAndCheckDiagnosticsForFile(sourceFile, cancellationToken), options),
+                filterSemanticDiagnostics(getBindAndCheckDiagnosticsForFile(sourceFile, cancellationToken), options),
                 getProgramDiagnostics(sourceFile)
             );
         }
@@ -1918,8 +1918,8 @@ namespace ts {
                 const isCheckJs = isCheckJsEnabledForFile(sourceFile, options);
                 const isTsNoCheck = !!sourceFile.checkJsDirective && sourceFile.checkJsDirective.enabled === false;
                 // By default, only type-check .ts, .tsx, 'Deferred' and 'External' files (external files are added by plugins)
-                const includeBindAndCheckDiagnostics = !isTsNoCheck && (sourceFile.scriptKind === ScriptKind.TS || sourceFile.scriptKind === ScriptKind.TSX ||
-                    sourceFile.scriptKind === ScriptKind.External || isCheckJs || sourceFile.scriptKind === ScriptKind.Deferred);
+                const includeBindAndCheckDiagnostics = !isTsNoCheck && (sourceFile.scriptKind === ScriptKind.TS || sourceFile.scriptKind === ScriptKind.TSX
+                    || sourceFile.scriptKind === ScriptKind.External || isCheckJs || sourceFile.scriptKind === ScriptKind.Deferred);
                 const bindDiagnostics: readonly Diagnostic[] = includeBindAndCheckDiagnostics ? sourceFile.bindDiagnostics : emptyArray;
                 const checkDiagnostics = includeBindAndCheckDiagnostics ? typeChecker.getDiagnostics(sourceFile, cancellationToken) : emptyArray;
 
@@ -3894,7 +3894,7 @@ namespace ts {
     }
 
     /*@internal*/
-    export function filterSemanticDiagnotics(diagnostic: readonly Diagnostic[], option: CompilerOptions): readonly Diagnostic[] {
+    export function filterSemanticDiagnostics(diagnostic: readonly Diagnostic[], option: CompilerOptions): readonly Diagnostic[] {
         return filter(diagnostic, d => !d.skippedOn || !option[d.skippedOn]);
     }
 

src/services/codefixes/fixSpelling.ts

@@ -3,7 +3,9 @@ namespace ts.codefix {
     const fixId = "fixSpelling";
     const errorCodes = [
         Diagnostics.Property_0_does_not_exist_on_type_1_Did_you_mean_2.code,
+        Diagnostics.Property_0_may_not_exist_on_type_1_Did_you_mean_2.code,
         Diagnostics.Cannot_find_name_0_Did_you_mean_1.code,
+        Diagnostics.Could_not_find_name_0_Did_you_mean_1.code,
         Diagnostics.Cannot_find_name_0_Did_you_mean_the_instance_member_this_0.code,
         Diagnostics.Cannot_find_name_0_Did_you_mean_the_static_member_1_0.code,
         Diagnostics._0_has_no_exported_member_named_1_Did_you_mean_2.code,

tests/baselines/reference/argumentsReferenceInConstructor3_Js.types

@@ -43,11 +43,11 @@ class B extends A {
 		 * @type object
 		 */
 		this.bar = super.arguments.foo;
->this.bar = super.arguments.foo : any
+>this.bar = super.arguments.foo : error
 >this.bar : any
 >this : this
 >bar : any
->super.arguments.foo : any
+>super.arguments.foo : error
 >super.arguments : { bar: {}; }
 >super : A
 >arguments : { bar: {}; }

tests/baselines/reference/jsObjectsMarkedAsOpenEnded.types

@@ -27,7 +27,7 @@ class C {
 
         this.member.a = 0;
 >this.member.a = 0 : 0
->this.member.a : any
+>this.member.a : error
 >this.member : {}
 >this : this
 >member : {}
@@ -48,7 +48,7 @@ var obj = {
 
 obj.property.a = 0;
 >obj.property.a = 0 : 0
->obj.property.a : any
+>obj.property.a : error
 >obj.property : {}
 >obj : { property: {}; }
 >property : {}

tests/baselines/reference/spellingUncheckedJS.symbols

@@ -0,0 +1,95 @@
+=== tests/cases/conformance/salsa/spellingUncheckedJS.js ===
+export var inModule = 1
+>inModule : Symbol(inModule, Decl(spellingUncheckedJS.js, 0, 10))
+
+inmodule.toFixed()
+
+function f() {
+>f : Symbol(f, Decl(spellingUncheckedJS.js, 1, 18))
+
+    var locals = 2 + true
+>locals : Symbol(locals, Decl(spellingUncheckedJS.js, 4, 7))
+
+    locale.toFixed()
+    // @ts-expect-error
+    localf.toExponential()
+    // @ts-expect-error
+    "this is fine"
+}
+class Classe {
+>Classe : Symbol(Classe, Decl(spellingUncheckedJS.js, 10, 1))
+
+    non = 'oui'
+>non : Symbol(Classe.non, Decl(spellingUncheckedJS.js, 11, 14))
+
+    methode() {
+>methode : Symbol(Classe.methode, Decl(spellingUncheckedJS.js, 12, 15))
+
+        // no error on 'this' references
+        return this.none
+>this : Symbol(Classe, Decl(spellingUncheckedJS.js, 10, 1))
+    }
+}
+class Derivee extends Classe {
+>Derivee : Symbol(Derivee, Decl(spellingUncheckedJS.js, 17, 1))
+>Classe : Symbol(Classe, Decl(spellingUncheckedJS.js, 10, 1))
+
+    methode() {
+>methode : Symbol(Derivee.methode, Decl(spellingUncheckedJS.js, 18, 30))
+
+        // no error on 'super' references
+        return super.none
+>super : Symbol(Classe, Decl(spellingUncheckedJS.js, 10, 1))
+    }
+}
+
+
+var object = {
+>object : Symbol(object, Decl(spellingUncheckedJS.js, 26, 3), Decl(spellingUncheckedJS.js, 29, 15), Decl(spellingUncheckedJS.js, 30, 18))
+
+    spaaace: 3
+>spaaace : Symbol(spaaace, Decl(spellingUncheckedJS.js, 26, 14))
+}
+object.spaaaace // error on read
+>object : Symbol(object, Decl(spellingUncheckedJS.js, 26, 3), Decl(spellingUncheckedJS.js, 29, 15), Decl(spellingUncheckedJS.js, 30, 18))
+
+object.spaace = 12 // error on write
+>object : Symbol(object, Decl(spellingUncheckedJS.js, 26, 3), Decl(spellingUncheckedJS.js, 29, 15), Decl(spellingUncheckedJS.js, 30, 18))
+
+object.fresh = 12 // OK
+>object : Symbol(object, Decl(spellingUncheckedJS.js, 26, 3), Decl(spellingUncheckedJS.js, 29, 15), Decl(spellingUncheckedJS.js, 30, 18))
+
+other.puuuce // OK, from another file
+>other : Symbol(other, Decl(other.js, 3, 3))
+
+new Date().getGMTDate() // OK, from another file
+>Date : Symbol(Date, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.scripthost.d.ts, --, --))
+
+// No suggestions for globals from other files
+const atoc = setIntegral(() => console.log('ok'), 500)
+>atoc : Symbol(atoc, Decl(spellingUncheckedJS.js, 36, 5))
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+
+AudioBuffin // etc
+Jimmy
+>Jimmy : Symbol(Jimmy, Decl(other.js, 0, 3))
+
+Jon
+
+=== tests/cases/conformance/salsa/other.js ===
+var Jimmy = 1
+>Jimmy : Symbol(Jimmy, Decl(other.js, 0, 3))
+
+var John = 2
+>John : Symbol(John, Decl(other.js, 1, 3))
+
+Jon // error, it's from the same file
+var other = {
+>other : Symbol(other, Decl(other.js, 3, 3))
+
+    puuce: 4
+>puuce : Symbol(puuce, Decl(other.js, 3, 13))
+}
+

tests/baselines/reference/spellingUncheckedJS.types

@@ -0,0 +1,152 @@
+=== tests/cases/conformance/salsa/spellingUncheckedJS.js ===
+export var inModule = 1
+>inModule : number
+>1 : 1
+
+inmodule.toFixed()
+>inmodule.toFixed() : error
+>inmodule.toFixed : error
+>inmodule : any
+>toFixed : any
+
+function f() {
+>f : () => void
+
+    var locals = 2 + true
+>locals : any
+>2 + true : any
+>2 : 2
+>true : true
+
+    locale.toFixed()
+>locale.toFixed() : error
+>locale.toFixed : error
+>locale : any
+>toFixed : any
+
+    // @ts-expect-error
+    localf.toExponential()
+>localf.toExponential() : error
+>localf.toExponential : error
+>localf : any
+>toExponential : any
+
+    // @ts-expect-error
+    "this is fine"
+>"this is fine" : "this is fine"
+}
+class Classe {
+>Classe : Classe
+
+    non = 'oui'
+>non : string
+>'oui' : "oui"
+
+    methode() {
+>methode : () => any
+
+        // no error on 'this' references
+        return this.none
+>this.none : error
+>this : this
+>none : any
+    }
+}
+class Derivee extends Classe {
+>Derivee : Derivee
+>Classe : Classe
+
+    methode() {
+>methode : () => any
+
+        // no error on 'super' references
+        return super.none
+>super.none : error
+>super : Classe
+>none : any
+    }
+}
+
+
+var object = {
+>object : { spaaace: number; }
+>{    spaaace: 3} : { spaaace: number; }
+
+    spaaace: 3
+>spaaace : number
+>3 : 3
+}
+object.spaaaace // error on read
+>object.spaaaace : error
+>object : { spaaace: number; }
+>spaaaace : any
+
+object.spaace = 12 // error on write
+>object.spaace = 12 : 12
+>object.spaace : error
+>object : { spaaace: number; }
+>spaace : any
+>12 : 12
+
+object.fresh = 12 // OK
+>object.fresh = 12 : 12
+>object.fresh : error
+>object : { spaaace: number; }
+>fresh : any
+>12 : 12
+
+other.puuuce // OK, from another file
+>other.puuuce : any
+>other : { puuce: number; }
+>puuuce : any
+
+new Date().getGMTDate() // OK, from another file
+>new Date().getGMTDate() : error
+>new Date().getGMTDate : error
+>new Date() : Date
+>Date : DateConstructor
+>getGMTDate : any
+
+// No suggestions for globals from other files
+const atoc = setIntegral(() => console.log('ok'), 500)
+>atoc : error
+>setIntegral(() => console.log('ok'), 500) : error
+>setIntegral : error
+>() => console.log('ok') : () => void
+>console.log('ok') : void
+>console.log : (...data: any[]) => void
+>console : Console
+>log : (...data: any[]) => void
+>'ok' : "ok"
+>500 : 500
+
+AudioBuffin // etc
+>AudioBuffin : error
+
+Jimmy
+>Jimmy : number
+
+Jon
+>Jon : error
+
+=== tests/cases/conformance/salsa/other.js ===
+var Jimmy = 1
+>Jimmy : number
+>1 : 1
+
+var John = 2
+>John : number
+>2 : 2
+
+Jon // error, it's from the same file
+>Jon : error
+
+var other = {
+>other : { puuce: number; }
+>{    puuce: 4} : { puuce: number; }
+
+    puuce: 4
+>puuce : number
+>4 : 4
+}
+

tests/cases/conformance/salsa/spellingUncheckedJS.ts

@@ -0,0 +1,51 @@
+// @noEmit: true
+// @allowJs: true
+// @filename: spellingUncheckedJS.js
+export var inModule = 1
+inmodule.toFixed()
+
+function f() {
+    var locals = 2 + true
+    locale.toFixed()
+    // @ts-expect-error
+    localf.toExponential()
+    // @ts-expect-error
+    "this is fine"
+}
+class Classe {
+    non = 'oui'
+    methode() {
+        // no error on 'this' references
+        return this.none
+    }
+}
+class Derivee extends Classe {
+    methode() {
+        // no error on 'super' references
+        return super.none
+    }
+}
+
+
+var object = {
+    spaaace: 3
+}
+object.spaaaace // error on read
+object.spaace = 12 // error on write
+object.fresh = 12 // OK
+other.puuuce // OK, from another file
+new Date().getGMTDate() // OK, from another file
+
+// No suggestions for globals from other files
+const atoc = setIntegral(() => console.log('ok'), 500)
+AudioBuffin // etc
+Jimmy
+Jon
+
+// @filename: other.js
+var Jimmy = 1
+var John = 2
+Jon // error, it's from the same file
+var other = {
+    puuce: 4
+}

tests/cases/fourslash/codeFixSpellingJs1.ts

@@ -0,0 +1,27 @@
+/// <reference path='fourslash.ts' />
+
+// @allowjs: true
+// @noEmit: true
+
+// @filename: a.js
+//// function f() {
+////     var locals = 2
+////     [|locale|].toFixed()
+////     return locals
+//// }
+
+verify.noErrors()
+verify.codeFixAvailable([
+    { description: "Change spelling to 'locals'" },
+]);
+
+verify.codeFix({
+    description: "Change spelling to 'locals'",
+    index: 0,
+    newFileContent:
+`function f() {
+    var locals = 2
+    locals.toFixed()
+    return locals
+}`,
+});

tests/cases/fourslash/codeFixSpellingJs2.ts

@@ -0,0 +1,16 @@
+/// <reference path='fourslash.ts' />
+
+// @allowjs: true
+// @noEmit: true
+
+// @filename: a.js
+//// export var inModule = 1
+//// [|inmodule|].toFixed()
+
+verify.codeFix({
+    description: "Change spelling to 'inModule'",
+    index: 0,
+    newFileContent:
+`export var inModule = 1
+inModule.toFixed()`,
+});

tests/cases/fourslash/codeFixSpellingJs3.ts

@@ -0,0 +1,21 @@
+/// <reference path='fourslash.ts' />
+
+// @allowjs: true
+// @noEmit: true
+
+// @filename: a.js
+//// class Classe {
+////     non = 'oui'
+////     methode() {
+////         // no error on 'this' references
+////         return this.none
+////     }
+//// }
+//// class Derivee extends Classe {
+////     methode() {
+////         // no error on 'super' references
+////         return super.none
+////     }
+//// }
+verify.noErrors()
+

tests/cases/fourslash/codeFixSpellingJs4.ts

@@ -0,0 +1,23 @@
+/// <reference path='fourslash.ts' />
+
+// @allowjs: true
+// @noEmit: true
+
+// @filename: a.js
+//// var object = {
+////     spaaace: 3
+//// }
+//// object.spaaaace // error on read
+//// object.spaace = 12 // error on write
+//// object.fresh = 12 // OK
+verify.codeFixAll({
+    fixId: "fixSpelling",
+    fixAllDescription: "Fix all detected spelling errors",
+    newFileContent:
+`var object = {
+    spaaace: 3
+}
+object.spaaace // error on read
+object.spaaace = 12 // error on write
+object.fresh = 12 // OK`,
+});

tests/cases/fourslash/codeFixSpellingJs5.ts

@@ -0,0 +1,26 @@
+/// <reference path='fourslash.ts' />
+
+// @allowjs: true
+// @noEmit: true
+
+// @filename: a.js
+//// var other = {
+////     puuce: 4
+//// }
+//// var Jimmy = 1
+//// var John = 2
+
+// @filename: b.js
+//// other.puuuce // OK, from another file
+//// new Date().getGMTDate() // OK, from another file
+//// window.argle // OK, from globalThis
+//// self.blargle // OK, from globalThis
+////
+//// // No suggestions for globals from other files
+//// const atoc = setIntegral(() => console.log('ok'), 500)
+//// AudioBuffin // etc
+//// Jimmy
+//// Jon
+
+
+verify.noErrors()

tests/cases/fourslash/codeFixSpellingJs6.ts

@@ -0,0 +1,56 @@
+/// <reference path='fourslash.ts' />
+
+// @allowjs: true
+// @checkjs: false
+// @noEmit: true
+// @filename: spellingUncheckedJS.js
+//// export var inModule = 1
+//// inmodule.toFixed()
+////
+//// function f() {
+////     var locals = 2 + true
+////     locale.toFixed()
+//// }
+//// class Classe {
+////     non = 'oui'
+////     methode() {
+////         // no error on 'this' references
+////         return this.none
+////     }
+//// }
+//// class Derivee extends Classe {
+////     methode() {
+////         // no error on 'super' references
+////         return super.none
+////     }
+//// }
+////
+////
+//// var object = {
+////     spaaace: 3
+//// }
+//// object.spaaaace // error on read
+//// object.spaace = 12 // error on write
+//// object.fresh = 12 // OK
+//// other.puuuce // OK, from another file
+//// new Date().getGMTDate() // OK, from another file
+////
+//// // No suggestions for globals from other files
+//// const atoc = setIntegral(() => console.log('ok'), 500)
+//// AudioBuffin // etc
+//// Jimmy
+//// Jon
+//// window.argle
+//// self.blargle
+
+// @filename: other.js
+//// var Jimmy = 1
+//// var John = 2
+//// Jon // error, it's from the same file
+//// var other = {
+////     puuce: 4
+//// }
+//// window.argle
+//// self.blargle
+
+verify.noErrors()

tests/cases/fourslash/codeFixSpellingJs7.ts

@@ -0,0 +1,57 @@
+/// <reference path='fourslash.ts' />
+
+// @allowjs: true
+// @noEmit: true
+// @filename: spellingUncheckedJS.js
+//// // @ts-nocheck
+//// export var inModule = 1
+//// inmodule.toFixed()
+////
+//// function f() {
+////     var locals = 2 + true
+////     locale.toFixed()
+//// }
+//// class Classe {
+////     non = 'oui'
+////     methode() {
+////         // no error on 'this' references
+////         return this.none
+////     }
+//// }
+//// class Derivee extends Classe {
+////     methode() {
+////         // no error on 'super' references
+////         return super.none
+////     }
+//// }
+////
+////
+//// var object = {
+////     spaaace: 3
+//// }
+//// object.spaaaace // error on read
+//// object.spaace = 12 // error on write
+//// object.fresh = 12 // OK
+//// other.puuuce // OK, from another file
+//// new Date().getGMTDate() // OK, from another file
+////
+//// // No suggestions for globals from other files
+//// const atoc = setIntegral(() => console.log('ok'), 500)
+//// AudioBuffin // etc
+//// Jimmy
+//// Jon
+//// window.argle
+//// self.blargle
+
+// @filename: other.js
+//// // @ts-nocheck
+//// var Jimmy = 1
+//// var John = 2
+//// Jon // error, it's from the same file
+//// var other = {
+////     puuce: 4
+//// }
+//// window.argle
+//// self.blargle
+
+verify.noErrors()

tests/cases/fourslash/codeFixSpellingJs8.ts

@@ -0,0 +1,10 @@
+/// <reference path='fourslash.ts' />
+
+// @allowjs: true
+// @noEmit: true
+
+// @filename: a.js
+//// var locals = {}
+//// // @ts-expect-error
+//// Object.keys(locale)
+verify.noErrors()

tests/cases/fourslash/codeFixUnusedIdentifier_delete_templateTag.ts

@@ -53,6 +53,7 @@ function second(p) { return p; }`,
 goTo.file("/both.js");
 verify.codeFix({
     description: "Remove template tag",
+    index: 0,
     newFileContent:
 `/**
  * */

tests/cases/fourslash/codeFixUnusedIdentifier_jsdocTypeParameter.ts

@@ -10,6 +10,7 @@
 
 verify.codeFix({
     description: "Remove type parameters",
+    index: 0,
     newFileContent:
 `/**
  * @type {() => void}

tests/cases/fourslash/convertToEs6Class_emptyCatchClause.ts

@@ -9,6 +9,7 @@
 
 verify.codeFix({
     description: "Convert function to an ES2015 class",
+    index: 0,
     newFileContent:
 `class MyClass {
     constructor() { }