Don't recommend to install '@types/foo' if that already exists

src/compiler/checker.ts

@@ -2283,16 +2283,24 @@ namespace ts {
         }
 
         function errorOnImplicitAnyModule(isError: boolean, errorNode: Node, { packageId, resolvedFileName }: ResolvedModuleFull, moduleReference: string): void {
-            const errorInfo = packageId && chainDiagnosticMessages(
-                /*details*/ undefined,
-                Diagnostics.Try_npm_install_types_Slash_0_if_it_exists_or_add_a_new_declaration_d_ts_file_containing_declare_module_0,
-                getMangledNameForScopedPackage(packageId.name));
+            const errorInfo = packageId
+                ? chainDiagnosticMessages(
+                    /*details*/ undefined,
+                    typesPackageExists(packageId.name)
+                        ? Diagnostics.If_the_0_package_actually_exposes_this_module_consider_sending_a_pull_request_to_amend_https_Colon_Slash_Slashgithub_com_SlashDefinitelyTyped_SlashDefinitelyTyped_Slashtree_Slashmaster_Slashtypes_Slash_0
+                        : Diagnostics.Try_npm_install_types_Slash_0_if_it_exists_or_add_a_new_declaration_d_ts_file_containing_declare_module_0,
+                    getMangledNameForScopedPackage(packageId.name))
+                : undefined;
             errorOrSuggestion(isError, errorNode, chainDiagnosticMessages(
                 errorInfo,
                 Diagnostics.Could_not_find_a_declaration_file_for_module_0_1_implicitly_has_an_any_type,
                 moduleReference,
                 resolvedFileName));
         }
+        function typesPackageExists(packageName: string): boolean {
+            return host.getSourceFiles().some(sf => !!sf.resolvedModules && !!forEachEntry(sf.resolvedModules, r =>
+                r && r.packageId && r.packageId.name === getTypesPackageName(packageName)));
+        }
 
         // An external module with an 'export =' declaration resolves to the target of the 'export =' declaration,
         // and an external module with no 'export =' declaration resolves to the module itself.

src/compiler/diagnosticMessages.json

@@ -3636,7 +3636,7 @@
         "category": "Message",
         "code": 6353
     },
-    
+
     "Project '{0}' is up to date with .d.ts files from its dependencies": {
         "category": "Message",
         "code": 6354
@@ -3836,6 +3836,10 @@
         "category": "Error",
         "code": 7039
     },
+    "If the '{0}' package actually exposes this module, consider sending a pull request to amend 'https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/{0}`": {
+        "category": "Error",
+        "code": 7040
+    },
     "You cannot rename this element.": {
         "category": "Error",
         "code": 8000

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -5752,6 +5752,7 @@ declare namespace ts {
         Enables_emit_interoperability_between_CommonJS_and_ES_Modules_via_creation_of_namespace_objects_for_all_imports_Implies_allowSyntheticDefaultImports: DiagnosticMessage;
         Type_originates_at_this_import_A_namespace_style_import_cannot_be_called_or_constructed_and_will_cause_a_failure_at_runtime_Consider_using_a_default_import_or_import_require_here_instead: DiagnosticMessage;
         Mapped_object_type_implicitly_has_an_any_template_type: DiagnosticMessage;
+        If_the_0_package_actually_exposes_this_module_consider_sending_a_pull_request_to_amend_https_Colon_Slash_Slashgithub_com_SlashDefinitelyTyped_SlashDefinitelyTyped_Slashtree_Slashmaster_Slashtypes_Slash_0: DiagnosticMessage;
         You_cannot_rename_this_element: DiagnosticMessage;
         You_cannot_rename_elements_that_are_defined_in_the_standard_TypeScript_library: DiagnosticMessage;
         import_can_only_be_used_in_a_ts_file: DiagnosticMessage;

tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.errors.txt

@@ -0,0 +1,35 @@
+/a.ts(2,25): error TS7016: Could not find a declaration file for module 'foo/sub'. '/node_modules/foo/sub.js' implicitly has an 'any' type.
+  If the 'foo' package actually exposes this module, consider sending a pull request to amend 'https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/foo`
+/a.ts(3,25): error TS7016: Could not find a declaration file for module 'bar/sub'. '/node_modules/bar/sub.js' implicitly has an 'any' type.
+  Try `npm install @types/bar` if it exists or add a new declaration (.d.ts) file containing `declare module 'bar';`
+
+
+==== /a.ts (2 errors) ====
+    import * as foo from "foo";
+    import * as fooSub from "foo/sub";
+                            ~~~~~~~~~
+!!! error TS7016: Could not find a declaration file for module 'foo/sub'. '/node_modules/foo/sub.js' implicitly has an 'any' type.
+!!! error TS7016:   If the 'foo' package actually exposes this module, consider sending a pull request to amend 'https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/foo`
+    import * as barSub from "bar/sub";
+                            ~~~~~~~~~
+!!! error TS7016: Could not find a declaration file for module 'bar/sub'. '/node_modules/bar/sub.js' implicitly has an 'any' type.
+!!! error TS7016:   Try `npm install @types/bar` if it exists or add a new declaration (.d.ts) file containing `declare module 'bar';`
+
+==== /node_modules/@types/foo/index.d.ts (0 errors) ====
+    export const foo: number;
+
+==== /node_modules/@types/foo/package.json (0 errors) ====
+    { "name": "@types/foo", "version": "1.2.3" }
+
+==== /node_modules/foo/sub.js (0 errors) ====
+    const x = 0;
+
+==== /node_modules/foo/package.json (0 errors) ====
+    { "name": "foo", "version": "1.2.3" }
+
+==== /node_modules/bar/sub.js (0 errors) ====
+    const x = 0;
+
+==== /node_modules/bar/package.json (0 errors) ====
+    { "name": "bar", "version": "1.2.3" }
+

tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.js

@@ -0,0 +1,29 @@
+//// [tests/cases/conformance/moduleResolution/untypedModuleImport_noImplicitAny_typesForPackageExist.ts] ////
+
+//// [index.d.ts]
+export const foo: number;
+
+//// [package.json]
+{ "name": "@types/foo", "version": "1.2.3" }
+
+//// [sub.js]
+const x = 0;
+
+//// [package.json]
+{ "name": "foo", "version": "1.2.3" }
+
+//// [sub.js]
+const x = 0;
+
+//// [package.json]
+{ "name": "bar", "version": "1.2.3" }
+
+//// [a.ts]
+import * as foo from "foo";
+import * as fooSub from "foo/sub";
+import * as barSub from "bar/sub";
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;

tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.symbols

@@ -0,0 +1,14 @@
+=== /a.ts ===
+import * as foo from "foo";
+>foo : Symbol(foo, Decl(a.ts, 0, 6))
+
+import * as fooSub from "foo/sub";
+>fooSub : Symbol(fooSub, Decl(a.ts, 1, 6))
+
+import * as barSub from "bar/sub";
+>barSub : Symbol(barSub, Decl(a.ts, 2, 6))
+
+=== /node_modules/@types/foo/index.d.ts ===
+export const foo: number;
+>foo : Symbol(foo, Decl(index.d.ts, 0, 12))
+

tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.types

@@ -0,0 +1,14 @@
+=== /a.ts ===
+import * as foo from "foo";
+>foo : typeof foo
+
+import * as fooSub from "foo/sub";
+>fooSub : any
+
+import * as barSub from "bar/sub";
+>barSub : any
+
+=== /node_modules/@types/foo/index.d.ts ===
+export const foo: number;
+>foo : number
+

tests/cases/conformance/moduleResolution/untypedModuleImport_noImplicitAny_typesForPackageExist.ts

@@ -0,0 +1,25 @@
+// @noImplicitReferences: true
+// @strict: true
+
+// @Filename: /node_modules/@types/foo/index.d.ts
+export const foo: number;
+
+// @Filename: /node_modules/@types/foo/package.json
+{ "name": "@types/foo", "version": "1.2.3" }
+
+// @Filename: /node_modules/foo/sub.js
+const x = 0;
+
+// @Filename: /node_modules/foo/package.json
+{ "name": "foo", "version": "1.2.3" }
+
+// @Filename: /node_modules/bar/sub.js
+const x = 0;
+
+// @Filename: /node_modules/bar/package.json
+{ "name": "bar", "version": "1.2.3" }
+
+// @Filename: /a.ts
+import * as foo from "foo";
+import * as fooSub from "foo/sub";
+import * as barSub from "bar/sub";