A const array can grow: push/pop/splice on an annotated const

tslang/lib/TypeScript/MLIRGenImpl.h

@@ -1455,8 +1455,17 @@ class MLIRGenImpl
             // mutating methods silently did nothing (they mutated a copy nobody kept)
             // and `arr[i] = v` segfaulted (write into read-only constant data).
             // Force the same real-storage + widening path as `let` for this case too.
+            //
+            // A `const` already typed `!ts.array<T>` (`const a: number[] = [1, 2]`, or an array
+            // returned by a call) needs it as well: push/pop/splice grow the array in place
+            // through a reference to it, and a bare SSA value has none. A ConstRef already
+            // aliases the storage it was read from, so it keeps that, and a narrowed view
+            // (addSafeCastStatement, a SafeCastOp) is the narrowed variable seen through
+            // another type, not an array of its own.
             MLIRTypeHelper mth(builder.getContext(), compileOptions);
-            needsIdentityStorage = mth.hasBoundMethodField(type) || isa<mlir_ts::ConstArrayType>(type);
+            needsIdentityStorage = mth.hasBoundMethodField(type) || isa<mlir_ts::ConstArrayType>(type)
+                || (isa<mlir_ts::ArrayType>(type) && !(varClass == VariableType::ConstRef)
+                    && !(initial && initial.getDefiningOp<mlir_ts::SafeCastOp>()));
             if (needsIdentityStorage)
             {
                 return mlir::success();

tslang/test/tester/CMakeLists.txt

@@ -333,6 +333,7 @@ tslang_add_test(NAME test-compile-00-arrays3 COMMAND test-runner "${PROJECT_SOUR
 tslang_add_test(NAME test-compile-00-arrays4-push-pop COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00array4_push_pop.ts")
 tslang_add_test(NAME test-compile-00-array-shift COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00array_shift.ts")
 tslang_add_test(NAME test-compile-00-array-splice COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00array_splice.ts")
+tslang_add_test(NAME test-compile-00-const-array-push COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00const_array_push.ts")
 tslang_add_test(NAME test-compile-00-arrays5-deconstruct COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00array5_deconst.ts")
 tslang_add_test(NAME test-compile-00-arrays6 COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00array6.ts")
 tslang_add_test(NAME test-compile-00-arrays7 COMMAND test-runner "${PROJECT_SOURCE_DIR}/test/tester/tests/00array7.ts")
@@ -782,6 +783,7 @@ tslang_add_test(NAME test-jit-00-arrays3 COMMAND test-runner -jit "${PROJECT_SOU
 tslang_add_test(NAME test-jit-00-arrays4-push-pop COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00array4_push_pop.ts")
 tslang_add_test(NAME test-jit-00-array-shift COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00array_shift.ts")
 tslang_add_test(NAME test-jit-00-array-splice COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00array_splice.ts")
+tslang_add_test(NAME test-jit-00-const-array-push COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00const_array_push.ts")
 tslang_add_test(NAME test-jit-00-arrays5-deconstruct COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00array5_deconst.ts")
 tslang_add_test(NAME test-jit-00-arrays6 COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00array6.ts")
 tslang_add_test(NAME test-jit-00-arrays7 COMMAND test-runner -jit "${PROJECT_SOURCE_DIR}/test/tester/tests/00array7.ts")
@@ -1546,6 +1548,7 @@ set(TSLANG_CORPUS
     00array_shift.ts
     00array_splice.ts
     00array_view.ts
+    00const_array_push.ts
     00array.ts
     00array2.ts
     00array3.ts

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

@@ -0,0 +1,39 @@
+// A const binding only forbids reassigning the name; the array it holds can still grow and
+// shrink. An annotated const (`const a: number[]`) and a const holding a call's result used to
+// be bare values, so push/pop/splice/length= had no array to change ("Can't get reference of
+// the array").
+const g: number[] = [1, 2];
+
+function make(): number[] {
+    return [7, 8];
+}
+
+function main() {
+    const a: number[] = [1, 2];
+    a.push(3);
+    assert(a.length == 3, "push length");
+    assert(a[2] == 3, "push value");
+
+    assert(a.pop() == 3, "pop value");
+    a.unshift(0);
+    assert(a.length == 3, "unshift length");
+    assert(a[0] == 0, "unshift value");
+
+    a.splice(1, 1);
+    assert(a.length == 2, "splice length");
+    assert(a[1] == 2, "splice value");
+
+    a.length = 1;
+    assert(a.length == 1, "length set");
+
+    const c = make();
+    c.push(9);
+    assert(c.length == 3, "call result length");
+    assert(c[2] == 9, "call result value");
+
+    g.push(3);
+    assert(g.length == 3, "global length");
+    assert(g[2] == 3, "global value");
+
+    print("done.");
+}