If import is used in the file, prefer that import specifier over calculating new one

src/compiler/checker.ts

@@ -4378,7 +4378,8 @@ namespace ts {
                         getProjectReferenceRedirect: fileName => host.getProjectReferenceRedirect(fileName),
                         isSourceOfProjectReferenceRedirect: fileName => host.isSourceOfProjectReferenceRedirect(fileName),
                         fileExists: fileName => host.fileExists(fileName),
-                        getCompilerOptions: () => host.getCompilerOptions()
+                        getCompilerOptions: () => host.getCompilerOptions(),
+                        getFileIncludeReasons: () => host.getFileIncludeReasons(),
                     } : undefined },
                     encounteredError: false,
                     visitedTypes: undefined,

src/compiler/emitter.ts

@@ -849,7 +849,8 @@ namespace ts {
             useCaseSensitiveFileNames: () => host.useCaseSensitiveFileNames(),
             getProgramBuildInfo: returnUndefined,
             getSourceFileFromReference: returnUndefined,
-            redirectTargetsMap: createMultiMap()
+            redirectTargetsMap: createMultiMap(),
+            getFileIncludeReasons: notImplemented,
         };
         emitFiles(
             notImplementedResolver,

src/compiler/moduleSpecifiers.ts

@@ -105,6 +105,14 @@ namespace ts.moduleSpecifiers {
         const moduleSourceFile = getSourceFileOfNode(moduleSymbol.valueDeclaration || getNonAugmentationDeclaration(moduleSymbol));
         const modulePaths = getAllModulePaths(importingSourceFile.path, moduleSourceFile.originalFileName, host);
 
+        const existingSpecifier = forEach(modulePaths, modulePath => forEach(
+            host.getFileIncludeReasons().get(toPath(modulePath.path, host.getCurrentDirectory(), info.getCanonicalFileName)),
+            reason => reason.kind === FileIncludeKind.Import && reason.file === importingSourceFile.path ?
+                getModuleNameStringLiteralAt(importingSourceFile, reason.index).text :
+                undefined
+        ));
+        if (existingSpecifier) return [existingSpecifier];
+
         const preferences = getPreferences(userPreferences, compilerOptions, importingSourceFile);
         const importedFileIsInNodeModules = some(modulePaths, p => p.isInNodeModules);
 

src/compiler/program.ts

@@ -1649,6 +1649,7 @@ namespace ts {
                 getProgramBuildInfo: () => program.getProgramBuildInfo && program.getProgramBuildInfo(),
                 getSourceFileFromReference: (file, ref) => program.getSourceFileFromReference(file, ref),
                 redirectTargetsMap,
+                getFileIncludeReasons: program.getFileIncludeReasons,
             };
         }
 
@@ -3973,7 +3974,8 @@ namespace ts {
         return res;
     }
 
-    function getModuleNameStringLiteralAt({ imports, moduleAugmentations }: SourceFile, index: number): StringLiteralLike {
+    /* @internal */
+    export function getModuleNameStringLiteralAt({ imports, moduleAugmentations }: SourceFile, index: number): StringLiteralLike {
         if (index < imports.length) return imports[index];
         let augIndex = imports.length;
         for (const aug of moduleAugmentations) {

src/compiler/types.ts

@@ -7947,6 +7947,7 @@ namespace ts {
         getProjectReferenceRedirect(fileName: string): string | undefined;
         isSourceOfProjectReferenceRedirect(fileName: string): boolean;
         getCompilerOptions(): CompilerOptions;
+        getFileIncludeReasons(): MultiMap<Path, FileIncludeReason>;
     }
 
     // Note: this used to be deprecated in our public API, but is still used internally

src/services/utilities.ts

@@ -1836,6 +1836,7 @@ namespace ts {
             isSourceOfProjectReferenceRedirect: fileName => program.isSourceOfProjectReferenceRedirect(fileName),
             getCompilerOptions: () => program.getCompilerOptions(),
             getNearestAncestorDirectoryWithPackageJson: maybeBind(host, host.getNearestAncestorDirectoryWithPackageJson),
+            getFileIncludeReasons: () => program.getFileIncludeReasons(),
         };
     }
 

src/testRunner/unittests/tsbuild/declarationEmit.ts

@@ -75,5 +75,44 @@ declare type MyNominal<T, Name extends string> = T & {
             }),
             commandLineArgs: ["--b", "/src/solution/tsconfig.json", "--verbose"]
         });
+
+        verifyTsc({
+            scenario: "declarationEmit",
+            subScenario: "when declaration file used inferred type from referenced project",
+            fs: () => loadProjectFromFiles({
+                "/src/tsconfig.json": JSON.stringify({
+                    compilerOptions: {
+                        composite: true,
+                        baseUrl: ".",
+                        paths: { "@fluentui/*": ["packages/*/src"] }
+                    }
+                }),
+                "/src/packages/pkg1/src/index.ts": Utils.dedent`
+export interface IThing {
+  a: string;
+}
+export interface IThings {
+  thing1: IThing;
+}`,
+                "/src/packages/pkg1/tsconfig.json": JSON.stringify({
+                    extends: "../../tsconfig",
+                    compilerOptions: { outDir: "lib" },
+                    include: ["src"]
+                }),
+                "/src/packages/pkg2/src/index.ts": Utils.dedent`
+import { IThings } from '@fluentui/pkg1';
+export function fn4() {
+  const a: IThings = { thing1: { a: 'b' } };
+  return a.thing1;
+}`,
+                "/src/packages/pkg2/tsconfig.json": JSON.stringify({
+                    extends: "../../tsconfig",
+                    compilerOptions: { outDir: "lib" },
+                    include: ["src"],
+                    references: [{ path: "../pkg1" }]
+                }),
+            }),
+            commandLineArgs: ["--b", "/src/packages/pkg2/tsconfig.json", "--verbose"]
+        });
     });
 }

tests/baselines/reference/tsbuild/declarationEmit/initial-build/when-declaration-file-used-inferred-type-from-referenced-project.js

@@ -0,0 +1,176 @@
+Input::
+//// [/lib/lib.d.ts]
+/// <reference no-default-lib="true"/>
+interface Boolean {}
+interface Function {}
+interface CallableFunction {}
+interface NewableFunction {}
+interface IArguments {}
+interface Number { toExponential: any; }
+interface Object {}
+interface RegExp {}
+interface String { charAt: any; }
+interface Array<T> { length: number; [n: number]: T; }
+interface ReadonlyArray<T> {}
+declare const console: { log(msg: any): void; };
+
+//// [/src/packages/pkg1/src/index.ts]
+export interface IThing {
+  a: string;
+}
+export interface IThings {
+  thing1: IThing;
+}
+
+//// [/src/packages/pkg1/tsconfig.json]
+{"extends":"../../tsconfig","compilerOptions":{"outDir":"lib"},"include":["src"]}
+
+//// [/src/packages/pkg2/src/index.ts]
+import { IThings } from '@fluentui/pkg1';
+export function fn4() {
+  const a: IThings = { thing1: { a: 'b' } };
+  return a.thing1;
+}
+
+//// [/src/packages/pkg2/tsconfig.json]
+{"extends":"../../tsconfig","compilerOptions":{"outDir":"lib"},"include":["src"],"references":[{"path":"../pkg1"}]}
+
+//// [/src/tsconfig.json]
+{"compilerOptions":{"composite":true,"baseUrl":".","paths":{"@fluentui/*":["packages/*/src"]}}}
+
+
+
+Output::
+/lib/tsc --b /src/packages/pkg2/tsconfig.json --verbose
+[12:00:00 AM] Projects in this build: 
+    * src/packages/pkg1/tsconfig.json
+    * src/packages/pkg2/tsconfig.json
+
+[12:00:00 AM] Project 'src/packages/pkg1/tsconfig.json' is out of date because output file 'src/packages/pkg1/lib/src/index.js' does not exist
+
+[12:00:00 AM] Building project '/src/packages/pkg1/tsconfig.json'...
+
+[12:00:00 AM] Project 'src/packages/pkg2/tsconfig.json' is out of date because output file 'src/packages/pkg2/lib/src/index.js' does not exist
+
+[12:00:00 AM] Building project '/src/packages/pkg2/tsconfig.json'...
+
+exitCode:: ExitStatus.Success
+
+
+//// [/src/packages/pkg1/lib/src/index.d.ts]
+export interface IThing {
+    a: string;
+}
+export interface IThings {
+    thing1: IThing;
+}
+
+
+//// [/src/packages/pkg1/lib/src/index.js]
+"use strict";
+exports.__esModule = true;
+
+
+//// [/src/packages/pkg1/lib/tsconfig.tsbuildinfo]
+{
+  "program": {
+    "fileInfos": {
+      "../../../../lib/lib.d.ts": {
+        "version": "3858781397-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ndeclare const console: { log(msg: any): void; };",
+        "signature": "3858781397-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ndeclare const console: { log(msg: any): void; };",
+        "affectsGlobalScope": true
+      },
+      "../src/index.ts": {
+        "version": "-2072077482-export interface IThing {\n  a: string;\n}\nexport interface IThings {\n  thing1: IThing;\n}",
+        "signature": "-5386205042-export interface IThing {\r\n    a: string;\r\n}\r\nexport interface IThings {\r\n    thing1: IThing;\r\n}\r\n",
+        "affectsGlobalScope": false
+      }
+    },
+    "options": {
+      "composite": true,
+      "baseUrl": "../../..",
+      "paths": {
+        "@fluentui/*": [
+          "packages/*/src"
+        ]
+      },
+      "pathsBasePath": "/src",
+      "outDir": "./",
+      "configFilePath": "../tsconfig.json"
+    },
+    "referencedMap": {},
+    "exportedModulesMap": {},
+    "semanticDiagnosticsPerFile": [
+      "../../../../lib/lib.d.ts",
+      "../src/index.ts"
+    ]
+  },
+  "version": "FakeTSVersion"
+}
+
+//// [/src/packages/pkg2/lib/src/index.d.ts]
+export declare function fn4(): import("@fluentui/pkg1").IThing;
+
+
+//// [/src/packages/pkg2/lib/src/index.js]
+"use strict";
+exports.__esModule = true;
+exports.fn4 = void 0;
+function fn4() {
+    var a = { thing1: { a: 'b' } };
+    return a.thing1;
+}
+exports.fn4 = fn4;
+
+
+//// [/src/packages/pkg2/lib/tsconfig.tsbuildinfo]
+{
+  "program": {
+    "fileInfos": {
+      "../../../../lib/lib.d.ts": {
+        "version": "3858781397-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ndeclare const console: { log(msg: any): void; };",
+        "signature": "3858781397-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ndeclare const console: { log(msg: any): void; };",
+        "affectsGlobalScope": true
+      },
+      "../../pkg1/lib/src/index.d.ts": {
+        "version": "-5386205042-export interface IThing {\r\n    a: string;\r\n}\r\nexport interface IThings {\r\n    thing1: IThing;\r\n}\r\n",
+        "signature": "-5386205042-export interface IThing {\r\n    a: string;\r\n}\r\nexport interface IThings {\r\n    thing1: IThing;\r\n}\r\n",
+        "affectsGlobalScope": false
+      },
+      "../src/index.ts": {
+        "version": "8515046367-import { IThings } from '@fluentui/pkg1';\nexport function fn4() {\n  const a: IThings = { thing1: { a: 'b' } };\n  return a.thing1;\n}",
+        "signature": "-9447422063-export declare function fn4(): import(\"@fluentui/pkg1\").IThing;\r\n",
+        "affectsGlobalScope": false
+      }
+    },
+    "options": {
+      "composite": true,
+      "baseUrl": "../../..",
+      "paths": {
+        "@fluentui/*": [
+          "packages/*/src"
+        ]
+      },
+      "pathsBasePath": "/src",
+      "outDir": "./",
+      "configFilePath": "../tsconfig.json"
+    },
+    "referencedMap": {
+      "../src/index.ts": [
+        "../../pkg1/lib/src/index.d.ts"
+      ]
+    },
+    "exportedModulesMap": {
+      "../src/index.ts": [
+        "../../pkg1/lib/src/index.d.ts"
+      ]
+    },
+    "semanticDiagnosticsPerFile": [
+      "../../../../lib/lib.d.ts",
+      "../../pkg1/lib/src/index.d.ts",
+      "../src/index.ts"
+    ]
+  },
+  "version": "FakeTSVersion"
+}
+