Add error for referencing referenced project input file

src/compiler/checker.ts

@@ -261,6 +261,7 @@ import {
     getCombinedLocalAndExportSymbolFlags,
     getCombinedModifierFlags,
     getCombinedNodeFlags,
+    getCommonSourceDirectoryOfConfig,
     getContainingClass,
     getContainingClassExcludingClassDecorators,
     getContainingClassStaticBlock,
@@ -353,6 +354,7 @@ import {
     getPropertyAssignmentAliasLikeExpression,
     getPropertyNameForPropertyNameNode,
     getPropertyNameFromType,
+    getRelativePathFromDirectory,
     getRelativePathFromFile,
     getResolutionDiagnostic,
     getResolutionModeOverride,
@@ -4665,6 +4667,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             else if (
                 compilerOptions.rewriteRelativeImportExtensions
                 && !(location.flags & NodeFlags.Ambient)
+                && !isDeclarationFileName(moduleReference)
                 && !isLiteralImportTypeNode(location)
                 && !isPartOfTypeOnlyImportOrExportDeclaration(location)
             ) {
@@ -4676,13 +4679,29 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                         getRelativePathFromFile(getNormalizedAbsolutePath(currentSourceFile.fileName, host.getCurrentDirectory()), resolvedModule.resolvedFileName, hostGetCanonicalFileName(host)),
                     );
                 }
-                else if (resolvedModule.resolvedUsingTsExtension && !shouldRewrite && !isDeclarationFileName(moduleReference) && sourceFileMayBeEmitted(sourceFile, host)) {
+                else if (resolvedModule.resolvedUsingTsExtension && !shouldRewrite && sourceFileMayBeEmitted(sourceFile, host)) {
                     error(
                         errorNode,
                         Diagnostics.This_import_uses_a_0_extension_to_resolve_to_an_input_TypeScript_file_but_will_not_be_rewritten_during_emit_because_it_is_not_a_relative_path,
                         getAnyExtensionFromPath(moduleReference),
                     );
                 }
+                else if (resolvedModule.resolvedUsingTsExtension && shouldRewrite) {
+                    const redirect = host.getResolvedProjectReferenceToRedirect(sourceFile.path);
+                    if (redirect) {
+                        const ignoreCase = !host.useCaseSensitiveFileNames();
+                        const ownRootDir = host.getCommonSourceDirectory();
+                        const otherRootDir = getCommonSourceDirectoryOfConfig(redirect.commandLine, ignoreCase);
+                        const rootDirPath = getRelativePathFromDirectory(ownRootDir, otherRootDir, ignoreCase);
+                        const outDirPath = getRelativePathFromDirectory(compilerOptions.outDir || ownRootDir, redirect.commandLine.options.outDir || otherRootDir, ignoreCase);
+                        if (rootDirPath !== outDirPath) {
+                            error(
+                                errorNode,
+                                Diagnostics.This_import_path_is_unsafe_to_rewrite_because_it_resolves_to_another_project_and_the_relative_path_between_the_projects_output_files_is_not_the_same_as_the_relative_path_between_its_input_files,
+                            );
+                        }
+                    }
+                }
             }
 
             if (sourceFile.symbol) {

src/compiler/diagnosticMessages.json

@@ -3956,6 +3956,10 @@
         "category": "Error",
         "code": 2875
     },
+    "This import path is unsafe to rewrite because it resolves to another project, and the relative path between the projects' output files is not the same as the relative path between its input files.": {
+        "category": "Error",
+        "code": 2876
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/rewriteRelativeImportExtensionsProjectReferences1.baseline

@@ -0,0 +1,19 @@
+// === Syntax and Semantic Diagnostics ===
+Syntactic Diagnostics for file '/tests/cases/fourslash/server/rewriteRelativeImportExtensionsProjectReferences1.ts':
+
+
+==== /tests/cases/fourslash/server/packages/common/src/index.ts (0 errors) ====
+    export {};
+==== /tests/cases/fourslash/server/packages/main/src/index.ts (0 errors) ====
+    import {} from "../../common/src/index.ts";
+
+Semantic Diagnostics for file '/tests/cases/fourslash/server/rewriteRelativeImportExtensionsProjectReferences1.ts':
+/tests/cases/fourslash/server/packages/main/src/index.ts(1,16): error TS2876: This import path is unsafe to rewrite because it resolves to another project, and the relative path between the projects' output files is not the same as the relative path between its input files.
+
+
+==== /tests/cases/fourslash/server/packages/common/src/index.ts (0 errors) ====
+    export {};
+==== /tests/cases/fourslash/server/packages/main/src/index.ts (1 errors) ====
+    import {} from "../../common/src/index.ts";
+                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2876: This import path is unsafe to rewrite because it resolves to another project, and the relative path between the projects' output files is not the same as the relative path between its input files.

tests/baselines/reference/rewriteRelativeImportExtensionsProjectReferences2.baseline

@@ -0,0 +1,16 @@
+// === Syntax and Semantic Diagnostics ===
+Syntactic Diagnostics for file '/tests/cases/fourslash/server/rewriteRelativeImportExtensionsProjectReferences2.ts':
+
+
+==== /tests/cases/fourslash/server/src/compiler/parser.ts (0 errors) ====
+    export {};
+==== /tests/cases/fourslash/server/src/services/services.ts (0 errors) ====
+    import {} from "../compiler/parser.ts";
+
+Semantic Diagnostics for file '/tests/cases/fourslash/server/rewriteRelativeImportExtensionsProjectReferences2.ts':
+
+
+==== /tests/cases/fourslash/server/src/compiler/parser.ts (0 errors) ====
+    export {};
+==== /tests/cases/fourslash/server/src/services/services.ts (0 errors) ====
+    import {} from "../compiler/parser.ts";