e81780e32e
lowerVarDecl (unannotated) and lowerDestructureDecl now clear target_type around the initializer lowering: a declaration without annotation provides no target, so int/float literals take their spec defaults (s64/f64) instead of the enclosing function's implicit-return type (x := 0 in a -> s8 fn was s8; big := 3000000000 in -> s32 silently wrapped to -1294967296). Regression: examples/0173-types-int-literal-default-s64.sx. The remaining explicit-annotation wrap (x : s8 = 300) is filed as issue 0112.
67 lines
3.0 KiB
Markdown
67 lines
3.0 KiB
Markdown
# 0112 — out-of-range int literal silently wraps into a narrower annotated target
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**Symptom.** An integer literal that does not fit its explicitly-annotated
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integer target truncates with no diagnostic: `x : s8 = 300;` binds 44,
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`y : u8 = 256;` binds 0. Expected: a compile-time error (the value is known
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exactly at compile time; this is the integer analogue of the float→int
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narrowing rule, which errors on non-exact `y : s64 = 1.5`).
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Split from issue 0111 (whose fix removed the *implicit* narrowing — an
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unannotated `x := 0` no longer adopts the fn return type — but the explicit
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annotation path keeps wrapping).
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## Reproduction
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```sx
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#import "modules/std.sx";
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main :: () {
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x : s8 = 300;
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print("x: {}\n", x);
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y : u8 = 256;
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print("y: {}\n", y);
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}
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```
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- **Observed** (current master): prints `x: 44` / `y: 0`, exit 0, no
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diagnostic.
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- **Expected**: compile error per literal, e.g.
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`integer literal 300 does not fit in s8 (range -128..127)`, and the analog
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for `256` / `u8 (range 0..255)`.
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Repro co-located: `issues/0112-int-literal-out-of-range-silent-wrap.sx`
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(unpinned until fixed).
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## Root cause (suspected area)
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`src/ir/lower/expr.zig` `.int_literal` arm (~1499): when `target_type` is an
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integer type, it emits `constInt(lit.value, tt)` with no fits-check — the
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value truncates at LLVM emission width. The annotated-decl path
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(`lowerVarDecl` with `type_annotation`, `src/ir/lower/stmt.zig` ~255) sets
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`target_type` to the annotation before lowering the initializer, so every
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annotated narrow decl funnels through this arm. Assignments to narrow
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lvalues (`b = 300` where `b: s8`) reach the same arm via `lowerAssignment`'s
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LHS-derived target and likely need the same check.
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## Investigation prompt (paste into a fresh session)
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> Fix issue 0112: an int literal that does not fit its integer target type
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> silently wraps. In the `.int_literal` arm of `lowerExpr`
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> (`src/ir/lower/expr.zig` ~1499), before adopting an integer `target_type`,
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> range-check `lit.value` against the target's signedness/width (the type
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> table knows both; mirror the bounds logic used by
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> `TypeResolver.integerLimitFor`). On overflow emit a diagnostic via
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> `self.diagnostics.addFmt(.err, node.span, ...)` naming the literal, the
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> type, and its range — do NOT silently fall back to s64 (REJECTED PATTERNS:
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> no silent fallback defaults); still return a `constInt` of the target type
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> so lowering continues to surface further errors. Audit sibling literal
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> sinks that bypass this arm (comptime folds, `lowerStructConstant`, global
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> initializers) for the same check.
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>
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> Verify: `issues/0112-int-literal-out-of-range-silent-wrap.sx` errors with
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> two diagnostics (s8/300, u8/256); boundary values still compile
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> (`x : s8 = -128` / `127`, `y : u8 = 0` / `255`, `m : u64` large literals).
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> `zig build && zig build test && bash tests/run_examples.sh` — any example
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> that relied on silent wrapping must be reviewed individually. Promote the
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> repro per the resolution flow (likely `examples/11xx-diagnostics-...`).
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