A sign-neutral iN is signed: it prints, widens and compares keeping its sign

tslang/include/TypeScript/LowerToLLVM/CastLogicHelper.h

@@ -106,9 +106,11 @@ class CastLogicHelper
             return castIntToString(in, tch.getIndexTypeBitwidth(), true);
         }
 
+        // a sign-neutral iN prints signed, as it compares and converts to number: `let a: i32 = -1` is -1,
+        // not 4294967295; only an unsigned uN prints unsigned
         if (isa<mlir::IntegerType>(inType) && isResString)
         {
-            return castIntToString(in, inLLVMType.getIntOrFloatBitWidth(), inType.isSignedInteger());
+            return castIntToString(in, inLLVMType.getIntOrFloatBitWidth(), !inType.isUnsignedInteger());
         }
 
         // a bigint is a signed i64; without this case it fell through to a bare inttoptr, and
@@ -151,17 +153,16 @@ class CastLogicHelper
             }
         }
 
-        // a signed integer keeps its sign as an index: `let n = s.length; n = -1` held 4294967295 under the
-        // zext in castLLVMTypesLogic
-        if (inType.isSignedInteger() && resType.isIndex() && resLLVMType.getIntOrFloatBitWidth() > inType.getIntOrFloatBitWidth())
+        // a wider integer keeps the value: a signed or sign-neutral (iN) one sign-extends, only an unsigned one
+        // zero-extends (castLLVMTypesLogic, which sees signless LLVM types only). `let c: i64 = -7` held
+        // 4294967289, `let n = s.length; n = -1` held 4294967295, and `i16` -300 compared as 65236.
+        if (auto inIntType = dyn_cast<mlir::IntegerType>(inType))
         {
-            return rewriter.create<LLVM::SExtOp>(loc, resLLVMType, in);
-        }
-
-        // TODO: should be in LLVM cast?
-        if (inType.isSignedInteger() && resType.isSignedInteger() && resType.getIntOrFloatBitWidth() > inType.getIntOrFloatBitWidth())
-        {
-            return rewriter.create<LLVM::SExtOp>(loc, resLLVMType, in);
+            if (!inIntType.isUnsigned() && inIntType.getWidth() > 1 && (isa<mlir::IntegerType>(resType) || resType.isIndex())
+                && resLLVMType.getIntOrFloatBitWidth() > inLLVMType.getIntOrFloatBitWidth())
+            {
+                return rewriter.create<LLVM::SExtOp>(loc, resLLVMType, in);
+            }
         }
 
         // an unsigned integer is converted to a float as unsigned: castLLVMTypesLogic only sees the

tslang/test/tester/CMakeLists.txt

@@ -398,6 +398,7 @@ tslang_add_test(NAME test-compile-00-generator-return COMMAND test-runner "${PRO
 tslang_add_test(NAME test-compile-00-return-inference-undefined COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00return_inference_undefined.ts")
 tslang_add_test(NAME test-compile-00-return-falls-off-end COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00return_falls_off_end.ts")
 tslang_add_test(NAME test-compile-00-nullish-values COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00nullish_values.ts")
+tslang_add_test(NAME test-compile-00-signless-int-signed COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00signless_int_signed.ts")
 tslang_add_test(NAME test-compile-00-intersection-type COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00intersection_type.ts")
 tslang_add_test(NAME test-compile-00-intersection-type-generic COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00intersection_type_generic.ts")
 tslang_add_test(NAME test-compile-00-length COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00length.ts")
@@ -879,6 +880,7 @@ tslang_add_test(NAME test-jit-00-generator-return COMMAND test-runner -jit "${PR
 tslang_add_test(NAME test-jit-00-return-inference-undefined COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00return_inference_undefined.ts")
 tslang_add_test(NAME test-jit-00-return-falls-off-end COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00return_falls_off_end.ts")
 tslang_add_test(NAME test-jit-00-nullish-values COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00nullish_values.ts")
+tslang_add_test(NAME test-jit-00-signless-int-signed COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00signless_int_signed.ts")
 tslang_add_test(NAME test-jit-00-union-global-init COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00union_global_init.ts")
 tslang_add_test(NAME test-jit-00-intersection-type COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00intersection_type.ts")
 tslang_add_test(NAME test-jit-00-intersection-type-generic COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00intersection_type_generic.ts")

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

@@ -0,0 +1,41 @@
+// a sign-neutral iN is signed: it prints, widens and compares keeping its sign (`let a: i32 = -1` printed
+// 4294967295, `let c: i64 = -7` held 4294967289, `i16` -300 compared as 65236); a uN stays unsigned
+function main() {
+    let a: i32 = -1;
+    assert(`${a}` == "-1", "i32 prints signed");
+    assert(a < 0, "i32 compares signed");
+    const n: number = a;
+    assert(n == -1, "i32 to number");
+
+    let b: i8 = -5;
+    assert(`${b}` == "-5", "i8 prints signed");
+
+    let c: i64 = -7;
+    assert(`${c}` == "-7", "i32 literal widens to i64 with its sign");
+    assert(c < 0, "i64 compares signed");
+
+    let d: i16 = -300;
+    assert(d < 0, "i16 widens to compare with its sign");
+    assert(`${d}` == "-300", "i16 prints signed");
+
+    const x: any = a;
+    assert(`${x}` == "-1", "i32 in any");
+
+    let k: i32 = -2;
+    let m: index = k;
+    assert(`${m}` == "-2", "i32 widens to index with its sign");
+
+    let big: i64 = -9000000000;
+    assert(`${big}` == "-9000000000" && big < 0, "i64");
+
+    // unsigned stays unsigned
+    let u: u32 = 4294967295;
+    assert(`${u}` == "4294967295", "u32 prints unsigned");
+    let u8v: u8 = 255;
+    let widened: s32 = u8v;
+    assert(widened == 255, "u8 widens with zeros");
+    let e: i64 = u;
+    assert(`${e}` == "4294967295", "u32 widens to i64 with zeros");
+
+    print("done.");
+}