From 8bd7ffa3f8a1ef4475ff7cc2ec9c3bf5c84dc830 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Mon, 26 Oct 2026 05:23:57 +0300
Subject: [PATCH] Fix macOS CI with default caching and integer migration
 (#31154)

* cgen: scope cleanup switch cases for older Apple Clang

* checker: let zero assignments leave reference sum variants

* math.big: pass signed byte counts to memory helpers

* checker: limit zero literal inspection to reference narrowing

* checker: stop loop narrowing scans before the current assignment

* tests: repair integer migration inputs for macOS self tests

* checker: return platform int for translated pointer differences

* examples: use signed byte counts for graphics buffers

* cgen: preserve headerless mmap bindings in cached modules

* fastc: repair pointer difference formatting and bootstrap fallback
---
 ci/README.md                                  |  9 ++++
 doc/docs.md                                   |  3 ++
 examples/gg/mandelbrot.v                      |  4 +-
 examples/gg/random_stars.v                    |  2 +-
 vlib/math/big/special_array_ops.v             |  4 +-
 vlib/v/gen/c/cleanc.v                         |  7 +++
 vlib/v/gen/c/detached_spawn_cleanup_test.v    | 41 +++++++++++++++++
 vlib/v/gen/c/mmap_headerless_test.v           |  7 +++
 vlib/v/gen/c/stmt.v                           | 10 +++--
 vlib/v/gen/c/sumtype_semantics_test.v         |  6 ++-
 vlib/v/gen/fastc/declaration_abi_test.v       | 27 ++++++++++++
 vlib/v/gen/fastc/stmt.v                       |  2 +-
 vlib/v/gen/fastc/str_intp.v                   |  6 ++-
 ...terpolation_struct_with_usize_field_test.v |  4 +-
 .../cast_interface_value_in_match_test.v      |  4 +-
 .../tests/translated_scalar_promotions_test.v |  4 ++
 vlib/v/types/checker_tail.v                   |  5 +++
 vlib/v/types/checker_tail_stmt.v              | 44 +++++++++++--------
 vlib/v/types/lexical_parent_cache_test.v      | 39 ++++++++++++++++
 19 files changed, 194 insertions(+), 34 deletions(-)

diff --git a/ci/README.md b/ci/README.md
index 8f4be21c7e..0aea98c083 100644
--- a/ci/README.md
+++ b/ci/README.md
@@ -113,6 +113,15 @@ source changes. Compiler and library edits deliberately preserve progress. Use
 artifacts needed by later tasks. Do not run multiple `ci` jobs in the same checkout
 concurrently; they share the checkpoint and build outputs.
 
+The macOS self-tests use default module caching. Generated cleanup for detached
+thread results must also compile with older Apple Clang versions that reject
+declarations immediately after `case` labels. The focused regression checks
+uncached, cold-cache and warm-cache builds, including nested error payloads:
+
+```sh
+./v test vlib/v/gen/c/detached_spawn_cleanup_test.v
+```
+
 ### Testing the resume behavior
 
 On macOS or Linux with a working V compiler, run:
diff --git a/doc/docs.md b/doc/docs.md
index e094eaf0cf..fafa2115f6 100644
--- a/doc/docs.md
+++ b/doc/docs.md
@@ -739,6 +739,7 @@ voidptr // this one is mostly used for [C interoperability](#v-and-c)
 `isize` and `usize` are deprecated. Replace `isize` with `int` and `usize` with `uint`.
 Use `uint` for pointer addresses and C `size_t` values to preserve
 the full unsigned range. Existing spellings still compile with deprecation warnings.
+Pointer subtraction returns `int`, including in translated C code.
 
 ### 128-bit integers
 
@@ -5174,6 +5175,8 @@ fixed-array elements.
 A mutable sum argument requires a variable of the sum type: it can replace the complete sum
 with another variant. Wrap a concrete value in a sum variable before passing it with `mut`.
 Inside a mutable smartcast, modifying a field modifies the selected payload in that sum.
+Assigning `0` to a sum with integer and reference variants selects the integer variant,
+including when its current variant is a reference.
 
 Sum payloads must have finite layout. References, dynamic arrays, and maps break recursive
 storage cycles; ordinary fields, options, and fixed arrays do not. A function variant stores
diff --git a/examples/gg/mandelbrot.v b/examples/gg/mandelbrot.v
index d9d65c452d..45309040a4 100644
--- a/examples/gg/mandelbrot.v
+++ b/examples/gg/mandelbrot.v
@@ -32,8 +32,8 @@ struct AppState {
 mut:
 	gg      &gg.Context = unsafe { nil }
 	iidx    int
-	pixels  &u32     = unsafe { &u32(vcalloc(pwidth * pheight * sizeof(u32))) }
-	npixels &u32     = unsafe { &u32(vcalloc(pwidth * pheight * sizeof(u32))) } // all drawing happens here, results are swapped at the end
+	pixels  &u32     = unsafe { &u32(vcalloc(pwidth * pheight * int(sizeof(u32)))) }
+	npixels &u32     = unsafe { &u32(vcalloc(pwidth * pheight * int(sizeof(u32)))) } // all drawing happens here, results are swapped at the end
 	view    ViewRect = ViewRect{-3.0773593290970673, 1.4952456603855397, -2.019938598189011, 2.3106642054225945}
 	scale   int      = 1
 	ntasks  int      = runtime.nr_jobs()
diff --git a/examples/gg/random_stars.v b/examples/gg/random_stars.v
index 39f4a12a0b..9c8036c46a 100644
--- a/examples/gg/random_stars.v
+++ b/examples/gg/random_stars.v
@@ -17,7 +17,7 @@ mut:
 @[direct_array_access]
 fn (mut state AppState) update() {
 	for {
-		unsafe { vmemset(&state.pixels, 0, pwidth * pheight * sizeof(gg.Color)) }
+		unsafe { vmemset(&state.pixels, 0, pwidth * pheight * int(sizeof(gg.Color))) }
 		state.draw_sky() or {}
 		time.sleep(30_000 * time.millisecond)
 	}
diff --git a/vlib/math/big/special_array_ops.v b/vlib/math/big/special_array_ops.v
index dc3f261ce4..d20313951e 100644
--- a/vlib/math/big/special_array_ops.v
+++ b/vlib/math/big/special_array_ops.v
@@ -291,8 +291,8 @@ fn left_shift_digits_in_place(mut a []u64, amount int) {
 		a.grow_len(amount)
 		sptr := &u8(a.data)
 		dptr := &u8(a.data) + u64(amount) * u64(elem_size)
-		vmemmove(dptr, sptr, u64(old_len) * u64(elem_size))
-		vmemset(sptr, 0, u64(amount) * u64(elem_size))
+		vmemmove(dptr, sptr, old_len * elem_size)
+		vmemset(sptr, 0, amount * elem_size)
 	}
 }
 
diff --git a/vlib/v/gen/c/cleanc.v b/vlib/v/gen/c/cleanc.v
index d2a77fd5af..d318110b9f 100644
--- a/vlib/v/gen/c/cleanc.v
+++ b/vlib/v/gen/c/cleanc.v
@@ -6057,6 +6057,13 @@ fn (g &FlatGen) core_native_header_is_redeclared(source_file string, include_arg
 		return false
 	}
 	relative := path[root.len + 6..]
+	// Cached module headers stand in for every source, but their owner can be
+	// any file in that module. Keep os's mmap declarations headerless on warm builds.
+	if !isnil(g.a) && source_file in g.a.cached_header_sources
+		&& relative.starts_with('os/') && include_arg == '<sys/mman.h>' {
+		return g.target.pointer_bits == 64 && g.target.os in ['macos', 'linux', 'android', 'termux',
+			'freebsd', 'openbsd', 'dragonfly']
+	}
 	if relative.starts_with('term/termios/termios_') && relative.ends_with('.c.v') {
 		return include_arg in ['<termios.h>', '<sys/ioctl.h>']
 	}
diff --git a/vlib/v/gen/c/detached_spawn_cleanup_test.v b/vlib/v/gen/c/detached_spawn_cleanup_test.v
index fff86a0bf1..9bb35d57b9 100644
--- a/vlib/v/gen/c/detached_spawn_cleanup_test.v
+++ b/vlib/v/gen/c/detached_spawn_cleanup_test.v
@@ -1,8 +1,49 @@
 module c
 
+import os
+import v.cmdexec
 import v.flat
 import v.types
 
+fn test_detached_spawn_nested_error_cleanup_compiles_as_c11() ! {
+	cc := os.find_abs_path_of_executable('clang') or { return }
+	dir := os.join_path(os.vtmp_dir(), 'detached_error_cleanup_${os.getpid()}')
+	os.mkdir_all(dir)!
+	defer { os.rmdir_all(dir) or {} }
+	source := os.join_path(dir, 'main.v')
+	os.write_file(source, 'struct NestedError { cause IError }
+fn (e NestedError) msg() string { return e.cause.msg() }
+fn (e NestedError) code() int { return 1 }
+interface Container { cause IError }
+type Choice = NestedError | int
+fn fail() ! { return NestedError{cause: error("nested")} }
+fn boxed() Container { return NestedError{cause: error("boxed")} }
+fn choice() Choice { return NestedError{cause: error("choice")} }
+fn main() {
+	spawn fail()
+	spawn boxed()
+	spawn choice()
+}
+')!
+	// Modern Clang accepts declarations after case labels as a C23 extension;
+	// older macOS CI compilers reject them. Exercise uncached, cold and warm builds.
+	for mode in ['uncached', 'cold', 'warm'] {
+		mut args := ['-cc', cc, '-cstrict', '-show-c-output', '-cflags',
+			'-std=gnu11 -Wc23-extensions -Wno-unknown-warning-option', '-o',
+			os.join_path(dir, 'program')]
+		if mode == 'uncached' {
+			args << '-nocache'
+		}
+		args << source
+		result := cmdexec.run_in_merged_with_env(@VEXE, args, dir, {
+			'V3CACHE': os.join_path(dir, 'cache')
+			'VJOBS':   '1'
+		})
+		assert result.exit_code == 0, '${mode}: ${result.output}'
+		assert !result.output.contains('label followed by a declaration'), '${mode}: ${result.output}'
+	}
+}
+
 fn test_detached_spawn_cleanup_reaches_deep_thread_results() {
 	mut ast := flat.FlatAst.new()
 	mut tc := types.TypeChecker.new(&ast)
diff --git a/vlib/v/gen/c/mmap_headerless_test.v b/vlib/v/gen/c/mmap_headerless_test.v
index 603698090c..444b191fee 100644
--- a/vlib/v/gen/c/mmap_headerless_test.v
+++ b/vlib/v/gen/c/mmap_headerless_test.v
@@ -30,6 +30,13 @@ fn test_mmap_header_ownership_is_limited_to_supported_shipped_bindings() {
 	a.cached_header_sources['/cache/os.vh'] = source
 	g.a = &a
 	assert g.core_native_header_is_redeclared('/cache/os.vh', '<sys/mman.h>')
+	a.cached_header_sources['/cache/os.vh'] = '/vroot/vlib/os/args.v'
+	assert g.core_native_header_is_redeclared('/cache/os.vh', '<sys/mman.h>')
+	a.cached_header_sources['/cache/user.vh'] = '/project/os/args.v'
+	assert !g.core_native_header_is_redeclared('/cache/user.vh', '<sys/mman.h>')
+	g.set_target(pref.target_from('linux', 'arm32')!)
+	assert !g.core_native_header_is_redeclared('/cache/os.vh', '<sys/mman.h>')
+	g.set_target(pref.target_from('macos', 'arm64')!)
 	g.no_builtin = true
 	assert !g.core_native_header_is_redeclared(source, '<sys/mman.h>')
 	g.no_builtin = false
diff --git a/vlib/v/gen/c/stmt.v b/vlib/v/gen/c/stmt.v
index 646dda5ba1..b3de9b153b 100644
--- a/vlib/v/gen/c/stmt.v
+++ b/vlib/v/gen/c/stmt.v
@@ -1738,11 +1738,12 @@ fn (mut g FlatGen) gen_ownership_drop_value_inner(typ types.Type, expr string, d
 					continue
 				}
 				concrete_ct := g.value_c_type(concrete_type)
-				g.writeln('case ${id}:')
+				g.writeln('case ${id}: {')
 				g.indent++
 				g.gen_ownership_drop_value_inner(concrete_type, '*((${concrete_ct}*)${object})', depth + 1, mut expanding)
 				g.writeln('break;')
 				g.indent--
+				g.writeln('}')
 			}
 			g.writeln('default: break;')
 			g.writeln('}')
@@ -1760,7 +1761,7 @@ fn (mut g FlatGen) gen_ownership_drop_value_inner(typ types.Type, expr string, d
 				resolved_variant := g.resolve_variant(sum_name_id, variant)
 				variant_type := g.tc.parse_canonical_type_cached(resolved_variant)
 				idx := g.sum_type_index(sum_name_id, resolved_variant)
-				g.writeln('case ${idx}:')
+				g.writeln('case ${idx}: {')
 				g.indent++
 				clean_variant_type := unalias_type(variant_type)
 				if clean_variant_type is types.Pointer {
@@ -1774,6 +1775,7 @@ fn (mut g FlatGen) gen_ownership_drop_value_inner(typ types.Type, expr string, d
 					g.writeln('}')
 					g.writeln('break;')
 					g.indent--
+					g.writeln('}')
 					continue
 				}
 				field := sum_field_name(flat.source_type_name(resolved_variant))
@@ -1781,6 +1783,7 @@ fn (mut g FlatGen) gen_ownership_drop_value_inner(typ types.Type, expr string, d
 				g.gen_ownership_drop_value_inner(variant_type, payload, depth + 1, mut expanding)
 				g.writeln('break;')
 				g.indent--
+				g.writeln('}')
 			}
 			g.writeln('default: break;')
 			g.writeln('}')
@@ -1813,7 +1816,7 @@ fn (mut g FlatGen) gen_ownership_drop_result_error(expr string, depth int, mut e
 			continue
 		}
 		concrete_ct := g.value_c_type(concrete_type)
-		g.writeln('case ${id}:')
+		g.writeln('case ${id}: {')
 		g.indent++
 		if concrete in ['MessageError', 'builtin.MessageError'] {
 			// MessageError is introduced by generated result/error lowering and can be
@@ -1824,6 +1827,7 @@ fn (mut g FlatGen) gen_ownership_drop_result_error(expr string, depth int, mut e
 		}
 		g.writeln('break;')
 		g.indent--
+		g.writeln('}')
 	}
 	g.writeln('default: break;')
 	g.writeln('}')
diff --git a/vlib/v/gen/c/sumtype_semantics_test.v b/vlib/v/gen/c/sumtype_semantics_test.v
index 842f8c3683..395941098c 100644
--- a/vlib/v/gen/c/sumtype_semantics_test.v
+++ b/vlib/v/gen/c/sumtype_semantics_test.v
@@ -185,6 +185,8 @@ fn main() {
  assert null is &Item
  assert voidptr(null as &Item) == unsafe { nil }
 }')!
-	result := os.exec([@VEXE, '-new-compiler', '-nocache', '-no-closures', 'run', path])
-	assert result.exit_code == 0, result.output
+	for flags in [['-nocache'], []string{}] {
+		result := os.exec([@VEXE, '-new-compiler', ...flags, '-no-closures', 'run', path])
+		assert result.exit_code == 0, result.output
+	}
 }
diff --git a/vlib/v/gen/fastc/declaration_abi_test.v b/vlib/v/gen/fastc/declaration_abi_test.v
index fc9d215ed6..7614de15c0 100644
--- a/vlib/v/gen/fastc/declaration_abi_test.v
+++ b/vlib/v/gen/fastc/declaration_abi_test.v
@@ -271,3 +271,30 @@ fn main() {
 	assert !source.contains('extern ptrdiff_t write(i32, const void*'), source
 	declaration_abi_run_c('target_write', source)
 }
+
+fn test_fastc_interpolates_native_pointer_differences() {
+	$if !macos && !linux {
+		return
+	}
+	mut prefs := pref.new_preferences()
+	prefs.vroot = @VEXEROOT
+	program := r"module main
+@[c_extern]
+fn C.native_difference() C.ptrdiff_t
+fn main() {
+	difference := C.native_difference()
+	assert '${difference}' == '-15'
+	assert '${difference:05d}' == '-0015'
+}
+"
+	for selfhost in [false, true] {
+		prefs.target_libc_headers = selfhost
+		source := if selfhost {
+			declaration_abi_generate('ptrdiff', program, prefs)
+		} else {
+			generate(program, 'ptrdiff.c.v', prefs) or { panic(err) }
+		}
+		assert source.contains('extern ptrdiff_t native_difference('), source
+		declaration_abi_run_c('ptrdiff_${selfhost}', '#include <stddef.h>\n' + source + '\nptrdiff_t native_difference(void) { return -15; }\n')
+	}
+}
diff --git a/vlib/v/gen/fastc/stmt.v b/vlib/v/gen/fastc/stmt.v
index 47b4f90107..03da9ce4f2 100644
--- a/vlib/v/gen/fastc/stmt.v
+++ b/vlib/v/gen/fastc/stmt.v
@@ -2239,7 +2239,7 @@ fn (mut g Parser) parse_parallel_assignment(initial_names []string, initial_mut
 			component_type := if i < component_types.len {
 				flat.source_type_name(component_types[i])
 			} else {
-				'uint', 'usize'
+				'uint'
 			}
 			c_name := fastc_c_identifier(name)
 			c_type := fastc_output_c_type(component_type)
diff --git a/vlib/v/gen/fastc/str_intp.v b/vlib/v/gen/fastc/str_intp.v
index 498c3aea7e..9b23fd2f27 100644
--- a/vlib/v/gen/fastc/str_intp.v
+++ b/vlib/v/gen/fastc/str_intp.v
@@ -492,11 +492,15 @@ fn (mut g Parser) read_interpolated_string() !string {
 		value_type := fastc_normalize_inferred_type(g.last_expression_type)
 		value_key := g.semantic_type_key(value_type)
 		alias_has_str_method := g.declared_kinds[flat.source_type_name(value_key)] == .alias_ && '${flat.source_type_name(value_key)}.str' in g.functions
-		interpolation_type := if alias_has_str_method {
+		mut interpolation_type := if alias_has_str_method {
 			flat.source_type_name(value_type)
 		} else {
 			flat.source_type_name(g.underlying_alias_type(value_type))
 		}
+		// C pointer differences use the signed pointer-sized integer formatter.
+		if interpolation_type == 'ptrdiff_t' {
+			interpolation_type = 'isize'
+		}
 		mut format_specifier := ''
 		if g.tok == .colon {
 			g.next()
diff --git a/vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_struct_with_usize_field_test.v b/vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_struct_with_usize_field_test.v
index 406a347ad6..d922770ab7 100644
--- a/vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_struct_with_usize_field_test.v
+++ b/vlib/v/tests/builtin_strings_and_interpolation/string_interpolation_struct_with_usize_field_test.v
@@ -22,11 +22,11 @@ fn test_stringified_usize_field_should_be_always_positive() {
 	assert sa.contains('f_isize: -1')
 	assert sa.contains('f_i64: -1')
 	assert sa.contains('f_i32: -1')
-	i := sa.split_into_lines().filter(it.contains('int'))[0]
+	i := sa.split_into_lines().filter(it.contains('f_isize:'))[0]
 	assert i.contains('-'), 'all `i` fields should be negative, but ${i} != ${a.f_isize}'
 
 	assert sa.contains('f_u64: 18446744073709551615')
 	assert sa.contains('f_u32: 4294967295')
-	u := sa.split_into_lines().filter(it.contains('uint'))[0]
+	u := sa.split_into_lines().filter(it.contains('f_usize:'))[0]
 	assert !u.contains('-'), 'all `u` fields should be positive, but ${u} != ${a.f_usize}'
 }
diff --git a/vlib/v/tests/casts/cast_interface_value_in_match_test.v b/vlib/v/tests/casts/cast_interface_value_in_match_test.v
index d50a63b9a7..504b06dcb1 100644
--- a/vlib/v/tests/casts/cast_interface_value_in_match_test.v
+++ b/vlib/v/tests/casts/cast_interface_value_in_match_test.v
@@ -2,7 +2,7 @@ interface Number2 {}
 
 fn t(v Number2) {
 	match v {
-		int, i32, int, i64 {
+		int, i32, i64 {
 			x := int(v)
 			println(x)
 			assert x == 42
@@ -22,4 +22,6 @@ fn t(v Number2) {
 
 fn test_cast_interface_value_in_match() {
 	t(int(42))
+	t(i32(42))
+	t(i64(42))
 }
diff --git a/vlib/v/tests/translated_scalar_promotions_test.v b/vlib/v/tests/translated_scalar_promotions_test.v
index d86f31ea48..9cd0c8beeb 100644
--- a/vlib/v/tests/translated_scalar_promotions_test.v
+++ b/vlib/v/tests/translated_scalar_promotions_test.v
@@ -215,6 +215,10 @@ fn test_translated_pointer_subtraction_retains_pointer_width() {
 	delta := unsafe { end - start }
 	assert typeof(delta).name == 'int'
 	assert delta == 3
+	assert sizeof(delta) == sizeof(voidptr)
+	reverse := unsafe { start - end }
+	assert typeof(reverse).name == 'int'
+	assert reverse == -3
 }
 
 fn translated_mixed_branch(flag bool) int {
diff --git a/vlib/v/types/checker_tail.v b/vlib/v/types/checker_tail.v
index 337eaf555f..cace95b02a 100644
--- a/vlib/v/types/checker_tail.v
+++ b/vlib/v/types/checker_tail.v
@@ -1067,6 +1067,11 @@ fn (tc &TypeChecker) assignment_preserves_smartcast(op flat.Op, lhs_id flat.Node
 // type (`x = 5` in `if mut x is int`), as in V 0.5.2. Any other value may select
 // another variant, so the narrowing ends.
 fn (tc &TypeChecker) assigned_value_keeps_narrowing(rhs_id flat.NodeId, rhs_type &Type, narrowed &Type) bool {
+	// An untyped zero selects a numeric variant rather than a null pointer.
+	if (narrowed is Pointer || (narrowed is Alias && narrowed.base_type is Pointer))
+		&& tc.zero_literal_can_be_pointer(rhs_id, narrowed) {
+		return false
+	}
 	return tc.expr_compatible(rhs_id, rhs_type, narrowed)
 		|| tc.pointer_value_compatible(rhs_type, narrowed)
 }
diff --git a/vlib/v/types/checker_tail_stmt.v b/vlib/v/types/checker_tail_stmt.v
index f29338b602..a7ff5229ba 100644
--- a/vlib/v/types/checker_tail_stmt.v
+++ b/vlib/v/types/checker_tail_stmt.v
@@ -16564,12 +16564,13 @@ fn (tc &TypeChecker) lexical_smartcast_type_in_parents(id flat.NodeId, key strin
 			// The loop condition re-narrows `key` at the top of every iteration, but a
 			// write to `key` earlier in the same iteration drops that narrowing for the
 			// rest of the body (the dynamic pass deletes the smartcast on assignment).
-			// Only reconstruct the condition smartcast when no preceding body statement,
-			// nor the statement holding `id`, writes `key`.
+			// Only reconstruct the condition smartcast when no statement before `id`
+			// in this iteration writes `key`.
 			if body_index >= 3 && tc.condition_may_smartcast_key(tc.a.child(parent, 1), key) {
 				for binding in tc.extract_smartcasts(tc.a.child(parent, 1)) {
 					if binding.name == key
-						&& !tc.for_body_writes_key_before(parent, body_index, current, key, binding.typ) {
+						&& !tc.for_body_writes_key_before(parent, body_index, current, id, key,
+							binding.typ) {
 						return binding.typ
 					}
 				}
@@ -16604,18 +16605,19 @@ fn (tc &TypeChecker) lexical_smartcast_type_in_parents(id flat.NodeId, key strin
 	return none
 }
 
-// for_body_writes_key_before reports whether any loop-body statement up to and
-// including `current` (the statement holding the checked node) ends the narrowing
-// of `key` to `narrowed` (see subtree_ends_narrowing). Such a write invalidates the
-// loop-condition narrowing for the rest of that iteration, so the lexical fallback
-// must not restore it.
-fn (tc &TypeChecker) for_body_writes_key_before(parent flat.Node, body_index int, current flat.NodeId, key string, narrowed Type) bool {
+// for_body_writes_key_before reports whether any loop-body statement before
+// the checked `target` within `current` ends the narrowing of `key` to `narrowed`
+// (see subtree_ends_narrowing). Such a write invalidates the loop-condition
+// narrowing for the rest of that iteration, so the lexical fallback must not restore it.
+fn (tc &TypeChecker) for_body_writes_key_before(parent flat.Node, body_index int, current flat.NodeId, target flat.NodeId, key string, narrowed Type) bool {
 	for i in 3 .. body_index {
 		if tc.subtree_ends_narrowing(tc.a.child(parent, i), key, narrowed, true) {
 			return true
 		}
 	}
-	return tc.subtree_ends_narrowing(current, key, narrowed, true)
+	// The current assignment has not stored its value while its RHS is resolved.
+	// Resolving it here would query the same loop smartcast recursively.
+	return tc.subtree_writes_key_before(current, target, key, narrowed, true)
 }
 
 // branch_writes_key_before reports whether a statement that runs before `target`
@@ -16633,15 +16635,23 @@ fn (tc &TypeChecker) branch_writes_key_before(branch_id flat.NodeId, target flat
 	if branch.kind !in [.block, .match_branch] {
 		return false
 	}
-	calls := branch.kind == .block
+	return tc.subtree_writes_key_before(branch_id, target, key, narrowed, branch.kind == .block)
+}
+
+fn (tc &TypeChecker) subtree_writes_key_before(root flat.NodeId, target flat.NodeId, key string, narrowed Type, calls bool) bool {
+	root_kind := tc.a.node(root).kind
 	mut child := target
+	if child == root {
+		return false
+	}
 	for _ in 0 .. 128 {
 		parent_id := tc.direct_parent_id(child)
 		if !tc.valid_node_id(parent_id) {
 			return false
 		}
-		if parent_id == branch_id {
-			return tc.statements_before_end_narrowing(parent_id, child, key, narrowed, calls)
+		if parent_id == root {
+			return root_kind in [.block, .match_branch]
+				&& tc.statements_before_end_narrowing(parent_id, child, key, narrowed, calls)
 		}
 		if tc.a.node(parent_id).kind in [.block, .match_branch, .for_stmt, .for_in_stmt, .lock_expr,
 			.defer_stmt, .select_branch]
@@ -16650,7 +16660,7 @@ fn (tc &TypeChecker) branch_writes_key_before(branch_id flat.NodeId, target flat
 		}
 		child = parent_id
 	}
-	return tc.statements_before_end_narrowing(branch_id, flat.empty_node, key, narrowed, calls)
+	return tc.statements_before_end_narrowing(root, flat.empty_node, key, narrowed, calls)
 }
 
 // statements_before_end_narrowing reports whether a child of `parent_id` before
@@ -20036,11 +20046,7 @@ fn (tc &TypeChecker) resolve_type_nonliteral(id flat.NodeId) Type {
 			}
 			if node.op in [.plus, .minus] {
 				if node.op == .minus && lt is Pointer && rt is Pointer {
-					return if tc.node_is_in_translated_file(id) {
-						builtin_isize_type
-					} else {
-						builtin_int_type
-					}
+					return builtin_int_type
 				}
 				if lt is Pointer && (rt_raw.is_integer()
 					|| (tc.node_is_in_translated_file(id) && translated_integer_type(rt_raw))) {
diff --git a/vlib/v/types/lexical_parent_cache_test.v b/vlib/v/types/lexical_parent_cache_test.v
index 0ef558d85a..cbbf488830 100644
--- a/vlib/v/types/lexical_parent_cache_test.v
+++ b/vlib/v/types/lexical_parent_cache_test.v
@@ -146,6 +146,45 @@ fn test_lexical_parent_cache_forks_own_slots_and_phase_resets_drop_storage() {
 	assert isnil(forked.lexical_parent_memo)
 }
 
+fn test_loop_narrowing_resolves_assignment_rhs_before_its_write() {
+	mut a := flat.FlatAst.new()
+	before := a.add_val(.ident, 'value')
+	lhs := a.add_val(.ident, 'value')
+	rhs_value := a.add_val(.ident, 'value')
+	one := a.add_val(.int_literal, '1')
+	rhs := lexical_parent_cache_children(mut a, .infix, [rhs_value, one])
+	a.nodes[int(rhs)].op = .plus
+	write := lexical_parent_cache_children(mut a, .assign, [lhs, rhs])
+	a.nodes[int(write)].op = .assign
+	after_int := a.add_val(.ident, 'value')
+	other_lhs := a.add_val(.ident, 'value')
+	other_rhs := a.add_val(.string_literal, 'changed')
+	other_write := lexical_parent_cache_children(mut a, .assign, [other_lhs, other_rhs])
+	a.nodes[int(other_write)].op = .assign
+	after_string := a.add_val(.ident, 'value')
+	nested := lexical_parent_cache_children(mut a, .block, [other_write, after_string])
+	cond := lexical_parent_cache_condition(mut a, 'value', 'int')
+	init := a.add(.empty)
+	post := a.add(.empty)
+	loop := lexical_parent_cache_children(mut a, .for_stmt, [init, cond, post, before, write,
+		after_int, nested])
+	lexical_parent_cache_children(mut a, .fn_decl, [loop])
+	for cached in [false, true] {
+		mut tc := TypeChecker.new(&a)
+		tc.cache_lexical_parents = cached
+		tc.build_direct_parent_index(&a)
+		tc.sum_types.set('Value', ['int', 'string'])
+		sum := Type(SumType{ name_id: flat.source_type_id('Value') })
+		tc.cur_scope.insert('value', sum)
+		tc.remember_expr_type(lhs, sum)
+		tc.remember_expr_type(other_lhs, sum)
+		assert tc.lexical_smartcast_type_in_parents(before, 'value', false)? == Type(int_)
+		assert tc.lexical_smartcast_type_in_parents(rhs_value, 'value', false)? == Type(int_)
+		assert tc.lexical_smartcast_type_in_parents(after_int, 'value', false)? == Type(int_)
+		assert tc.lexical_smartcast_type_in_parents(after_string, 'value', false) == none
+	}
+}
+
 fn test_lexical_parent_cache_matches_uncached_reachability_and_diagnostics() {
 	path := os.join_path(os.vtmp_dir(), 'v3_lexical_parent_differential_${os.getpid()}.v')
 	os.write_file(path, 'module main