A declared function redeclared: one declaration, or a clear error

tslang/lib/TypeScript/MLIRGenFunctions.cpp

@@ -597,6 +597,32 @@ namespace mlirgen
             return mlir::success();
         }
 
+        // A declared function binds one external symbol, and that has one signature: a second
+        // declaration of it with another was "redefinition of symbol" from the verifier. The same
+        // declaration again - one C function in two .d.ts files - is left to the first.
+        if (!functionDeclarationAST->body)
+        {
+            auto [fullName, name] = getNameOfFunction(functionDeclarationAST, genContext);
+            auto declared = declaredFunctions.find(fullName);
+            if (declared == declaredFunctions.end() || declared->second.second != theModule.getOperation())
+            {
+                declaredFunctions[fullName] = {functionDeclarationAST, theModule.getOperation()};
+            }
+            else if (declared->second.first != functionDeclarationAST)
+            {
+                if (print(declared->second.first) == print(functionDeclarationAST))
+                {
+                    return mlir::success();
+                }
+
+                emitError(loc(functionDeclarationAST))
+                    << "'" << name << "' is declared again with another signature: a declared function is one external "
+                    << "symbol, so it can't have overloads. Declare it once, with optional or union parameters, or "
+                    << "give each signature a name of its own and bind them with @linkname";
+                return mlir::failure();
+            }
+        }
+
         auto funcGenContext = GenContext(genContext);
         funcGenContext.clearScopeVars();
         // declaring function which is nested and object should not have this context (unless it is part of object declaration)

tslang/lib/TypeScript/MLIRGenImpl.h

@@ -12706,6 +12706,11 @@ class MLIRGenImpl
     // imports a) stops instead of recursing until the stack overflows.
     llvm::StringSet<> filesInProgress;
 
+    // the declaration (no body) each declared function's full name came from, and the module it was
+    // generated into - discovery's is thrown away, and a library's __decls is parsed again for the
+    // next pass; see mlirGen(FunctionDeclaration)
+    std::map<std::string, std::pair<FunctionDeclaration, mlir::Operation *>> declaredFunctions;
+
     // set while an `import { a as b }` alias is resolved to its target (resolveImportAlias)
     bool resolvingImportAlias = false;
 

tslang/test/tester/CMakeLists.txt

@@ -274,6 +274,7 @@ tslang_add_test(NAME test-compile-00-global-const-object-method COMMAND test-run
 tslang_add_test(NAME test-compile-00-funcs COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00funcs.ts")
 tslang_add_test(NAME test-compile-00-funcs-capture COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00funcs_capture.ts")
 tslang_add_test(NAME test-compile-00-funcs-vararg COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00funcs_vararg.ts")
+tslang_add_test(NAME test-compile-00-declare-function-twice COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00declare_function_twice.ts")
 tslang_add_test(NAME test-compile-00-function-overloads COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00function_overloads.ts")
 tslang_add_test(NAME test-compile-01-funcs-vararg COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/01funcs_vararg.ts")
 # printf is avaliable in JIT only, C has snprintf
@@ -720,6 +721,7 @@ tslang_add_test(NAME test-jit-00-global-const-object-method COMMAND test-runner
 tslang_add_test(NAME test-jit-00-funcs COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00funcs.ts")
 tslang_add_test(NAME test-jit-00-funcs-capture COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00funcs_capture.ts")
 tslang_add_test(NAME test-jit-00-funcs-vararg COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00funcs_vararg.ts")
+tslang_add_test(NAME test-jit-00-declare-function-twice COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00declare_function_twice.ts")
 tslang_add_test(NAME test-jit-00-function-overloads COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00function_overloads.ts")
 tslang_add_test(NAME test-jit-01-funcs-vararg COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/01funcs_vararg.ts")
 tslang_add_test(NAME test-jit-02-funcs-vararg COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/02funcs_vararg.ts")
@@ -2465,6 +2467,16 @@ endforeach()
 # parameter, and varargs with and without extra arguments.
 tslang_add_test(NAME test-compile-call-arity-positive COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/call-arity/positive.ts")
 
+# A declared function with a second signature: one external symbol has one signature, and the
+# error says so (it was "redefinition of symbol").
+add_test(NAME test-compile-declare-overloads-error
+         COMMAND $<TARGET_FILE:tslang> --emit=obj --no-default-lib -mm=none
+                 "${PROJECT_SOURCE_DIR}/test/tester/declare-overloads/overload.ts"
+                 -o "${CMAKE_CURRENT_BINARY_DIR}/declare-overloads.obj")
+set_tests_properties(test-compile-declare-overloads-error
+                     PROPERTIES PASS_REGULAR_EXPRESSION "'abs' is declared again with another signature"
+                                FAIL_REGULAR_EXPRESSION "Stack dump|Assertion failed|redefinition of symbol")
+
 # The shared-component tier under the other two models. A shared library records the model
 # it was built under, so both halves of a pair are built with the same flag - which is what
 # these run. The file pairs are the default model's, verbatim.

tslang/test/tester/declare-overloads/overload.ts

@@ -0,0 +1,8 @@
+// A declared function is one external symbol with one signature: a second signature is an error
+// that says so. It used to be "redefinition of symbol" from the verifier.
+declare function abs(x: i32): i32;
+declare function abs(x: i32, y: i32): i32;
+
+function main() {
+    print(abs(-3));
+}

tslang/test/tester/tests/00declare_function_twice.ts

@@ -0,0 +1,9 @@
+// The same declared function twice - one C function declared in two .d.ts files - is one
+// declaration. It used to be "redefinition of symbol".
+declare function abs(x: i32): i32;
+declare function abs(x: i32): i32;
+
+function main() {
+    assert(abs(-3) == 3);
+    print("done.");
+}