# 0112 — out-of-range int literal silently wraps into a narrower annotated target

**Symptom.** An integer literal that does not fit its explicitly-annotated
integer target truncates with no diagnostic: `x : s8 = 300;` binds 44,
`y : u8 = 256;` binds 0. Expected: a compile-time error (the value is known
exactly at compile time; this is the integer analogue of the float→int
narrowing rule, which errors on non-exact `y : s64 = 1.5`).

Split from issue 0111 (whose fix removed the *implicit* narrowing — an
unannotated `x := 0` no longer adopts the fn return type — but the explicit
annotation path keeps wrapping).

## Reproduction

```sx
#import "modules/std.sx";

main :: () {
    x : s8 = 300;
    print("x: {}\n", x);
    y : u8 = 256;
    print("y: {}\n", y);
}
```

- **Observed** (current master): prints `x: 44` / `y: 0`, exit 0, no
  diagnostic.
- **Expected**: compile error per literal, e.g.
  `integer literal 300 does not fit in s8 (range -128..127)`, and the analog
  for `256` / `u8 (range 0..255)`.

Repro co-located: `issues/0112-int-literal-out-of-range-silent-wrap.sx`
(unpinned until fixed).

## Root cause (suspected area)

`src/ir/lower/expr.zig` `.int_literal` arm (~1499): when `target_type` is an
integer type, it emits `constInt(lit.value, tt)` with no fits-check — the
value truncates at LLVM emission width. The annotated-decl path
(`lowerVarDecl` with `type_annotation`, `src/ir/lower/stmt.zig` ~255) sets
`target_type` to the annotation before lowering the initializer, so every
annotated narrow decl funnels through this arm. Assignments to narrow
lvalues (`b = 300` where `b: s8`) reach the same arm via `lowerAssignment`'s
LHS-derived target and likely need the same check.

## Investigation prompt (paste into a fresh session)

> Fix issue 0112: an int literal that does not fit its integer target type
> silently wraps. In the `.int_literal` arm of `lowerExpr`
> (`src/ir/lower/expr.zig` ~1499), before adopting an integer `target_type`,
> range-check `lit.value` against the target's signedness/width (the type
> table knows both; mirror the bounds logic used by
> `TypeResolver.integerLimitFor`). On overflow emit a diagnostic via
> `self.diagnostics.addFmt(.err, node.span, ...)` naming the literal, the
> type, and its range — do NOT silently fall back to s64 (REJECTED PATTERNS:
> no silent fallback defaults); still return a `constInt` of the target type
> so lowering continues to surface further errors. Audit sibling literal
> sinks that bypass this arm (comptime folds, `lowerStructConstant`, global
> initializers) for the same check.
>
> Verify: `issues/0112-int-literal-out-of-range-silent-wrap.sx` errors with
> two diagnostics (s8/300, u8/256); boundary values still compile
> (`x : s8 = -128` / `127`, `y : u8 = 0` / `255`, `m : u64` large literals).
> `zig build && zig build test && bash tests/run_examples.sh` — any example
> that relied on silent wrapping must be reviewed individually. Promote the
> repro per the resolution flow (likely `examples/11xx-diagnostics-...`).