lang: array-typed '::' consts as immutable globals (PLAN-CONST-AGG step 1)

K : [4]s64 : .[...] and the untyped A :: .[1, 2, 3] register as
is_const globals: one storage, reads GEP it, dead-global elimination
drops unused ones, source-aware reads come free via selectGlobalAuthor.

- registerConstArrayGlobal (scanDecls pass 2): typed via the annotation
  (array-ness + dimension/count checked), untyped via element-type
  unification — all ints s64; ANY float promotes the element type to
  f64 with ints converting exactly; bool/string homogeneous; a
  non-numeric mix or non-inferable element asks for an annotation.
- constExprValue converts int elements into float destinations exactly
  (the int+float promotion rule, element-wise).
- emitGlobals marks is_const globals LLVMSetGlobalConstant — also flips
  the comptime-backed #run globals and __sx_default_context to
  'constant' (37 pinned IR snapshots regenerated; runtime unchanged).
- Element shapes: nested arrays, struct elements, strings, bools.
  Non-constant elements / dim mismatch / mixed types diagnose loudly.

Examples: 0177 (feature matrix incl. @K reads through *[4]s64 — needs
the 0117 fix), 1159/1160/1161 (diagnostics), 0837 repointed to values.

examples/0177-types-array-consts.sx

@@ -0,0 +1,34 @@
+// Array-typed `::` constants are IMMUTABLE GLOBALS: one storage, reads
+// GEP it, the emitter marks it constant, dead-global elimination drops
+// unused ones. Typed (`K : [4]s64 : .[...]`) and untyped (`A :: .[...]`,
+// element type inferred — all ints s64; any float promotes the element
+// type to f64 with ints converting exactly; bool/string homogeneous).
+// Element shapes cover nested aggregates. Reads are normal array values:
+// indexing, .len, by-value copies (independent of the const), passing to
+// fixed-array params, and @-address (reads through *[4]s64 — issue 0117).
+
+#import "modules/std.sx";
+
+K : [4]s64 : .[11, 22, 33, 44];
+A :: .[1, 2, 3];
+M :: .[1, 2.2, 3];
+F : [2]f64 : .[1, 2.5];
+S :: .["alpha", "beta"];
+B :: .[true, false, true];
+P :: struct { x, y: s64; }
+PTS : [2]P : .[P.{ x = 1, y = 2 }, P.{ x = 3, y = 4 }];
+GRID : [2][2]s64 : .[.[1, 2], .[3, 4]];
+
+sum :: (xs: [4]s64) -> s64 { xs[0] + xs[1] + xs[2] + xs[3] }
+
+main :: () {
+    print("typed={} untyped={} len={}\n", K[2], A[1], K.len);
+    print("mixed={} {} {} intfloat={}\n", M[0], M[1], M[2], F[0]);
+    print("str={} bool={} pt={} grid={}\n", S[1], B[2], PTS[1].y, GRID[1][0]);
+    k := K;
+    k[0] = 99;
+    print("copy={} const={}\n", k[0], K[0]);
+    print("sum={}\n", sum(K));
+    p := @K;
+    print("via-ptr={}\n", p[2]);
+}

examples/0837-modules-array-const-no-cross-borrow.sx

@@ -1,11 +1,11 @@
-// An ARRAY-typed `::` const (`K : [4]s64 : .[...]`) is not a supported
+// An ARRAY-typed `::` const is an immutable global owned by its module.
-// module-const shape — its own module's read diagnoses cleanly as
+// Cross-module: the main file's scalar `K : s64 : 4` and h.sx's array
-// unresolved. The own author OWNS the name: the read must never borrow
+// `K : [4]s64 : .[...]` coexist — each module's bare `K` binds its OWN
-// another module's same-named scalar const (which used to type `K[2]`
+// author (h's use_k reads ITS array, main's K stays the scalar 4).
-// against the scalar and panic at LLVM emission).
 //
-// Regression (issue 0115). When array `::` consts land, repoint this
+// Regression (issue 0115): h.sx's read used to borrow main's scalar K
-// example at the new behavior.
+// and panic at LLVM emission; before array consts landed (PLAN-CONST-AGG
+// step 1) the shape was a clean "unresolved" diagnostic.
 
 #import "modules/std.sx";
 h :: #import "0837-modules-array-const-no-cross-borrow/h.sx";
@@ -13,5 +13,5 @@ h :: #import "0837-modules-array-const-no-cross-borrow/h.sx";
 K : s64 : 4;
 
 main :: () {
-    print("{}\n", h.use_k());
+    print("{} {}\n", K, h.use_k());
 }

examples/1159-diagnostics-array-const-mixed-elements.sx

@@ -0,0 +1,12 @@
+// An untyped array-literal constant infers its element type from the
+// elements (ints -> s64; a numeric int/float mix promotes to f64). A
+// NON-NUMERIC mix has no unified element type — diagnosed, with the
+// annotation as the fix.
+
+#import "modules/std.sx";
+
+BAD :: .["alpha", 1];
+
+main :: () {
+    print("{}\n", BAD[0]);
+}

examples/1160-diagnostics-array-const-runtime-element.sx

@@ -0,0 +1,12 @@
+// An array constant's elements must be compile-time constants — a call
+// (or any runtime expression) in an element slot is diagnosed. `#run`
+// is the tool for computed constants.
+
+#import "modules/std.sx";
+
+f :: () -> s64 { 7 }
+BAD : [2]s64 : .[1, f()];
+
+main :: () {
+    print("{}\n", BAD[0]);
+}

examples/1161-diagnostics-array-const-dim-mismatch.sx

@@ -0,0 +1,10 @@
+// A typed array constant's annotation dimension must match the
+// initializer's element count.
+
+#import "modules/std.sx";
+
+BAD : [3]s64 : .[1, 2];
+
+main :: () {
+    print("{}\n", BAD[0]);
+}

examples/expected/0031-basic-local-fn-return.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.465 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.466 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0032-basic-ufcs-return-type.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.465 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.466 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0044-basic-default-arg-expansion.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0107-types-int-cmp-in-float-ternary.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0177-types-array-consts.exit

@@ -0,0 +1 @@
+0

examples/expected/0177-types-array-consts.stderr

@@ -0,0 +1 @@
+

examples/expected/0177-types-array-consts.stdout

@@ -0,0 +1,6 @@
+typed=33 untyped=2 len=4
+mixed=1.000000 2.200000 3.000000 intfloat=1.000000
+str=beta bool=true pt=4 grid=3
+copy=99 const=11
+sum=110
+via-ptr=33

examples/expected/0200-generics-generic.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0201-generics-generic-struct.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0301-closures-fn-pointers.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0400-protocols-impl-for-builtin.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0413-protocols-parameterized-protocol-value.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @__VL__s64__IntCell__vtable = internal constant { ptr } { ptr @__thunk_IntCell_VL__s64_get }
 @__VL__string__StrCell__vtable = internal constant { ptr } { ptr @__thunk_StrCell_VL__string_get }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1

examples/expected/0414-protocols-generic-struct-protocol-erase.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @__VL__s64__IntCell__vtable = internal constant { ptr } { ptr @__thunk_IntCell_VL__s64_get }
 @__VL__s64__Combined__s64__s64__vtable = internal constant { ptr } { ptr @__thunk_Combined__s64__s64_VL__s64_get }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1

examples/expected/0416-protocols-auto-type-erasure.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @__Counter__SimpleCounter__vtable = internal constant { ptr, ptr } { ptr @__thunk_SimpleCounter_Counter_inc, ptr @__thunk_SimpleCounter_Counter_get }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.466 = private unnamed_addr constant [2 x i8] c"0\00", align 1

examples/expected/0507-packs-pack-mono-dedup.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0513-packs-pack-mixed-comptime.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0518-packs-pack-value-dispatch.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0528-packs-protocol-pack-methods.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/0837-modules-array-const-no-cross-borrow.exit

@@ -1 +1 @@
-1
+0

examples/expected/0837-modules-array-const-no-cross-borrow.stderr

@@ -1,5 +1 @@
-error: unresolved 'K' (in examples/0837-modules-array-const-no-cross-borrow/h.sx fn use_k)
+
-  --> examples/0837-modules-array-const-no-cross-borrow/h.sx:2:22
-   |
- 2 | use_k :: () -> s64 { K[2] }
-   |                      ^

examples/expected/0837-modules-array-const-no-cross-borrow.stdout

@@ -1 +1 @@
-
+4 33

examples/expected/0903-optionals-optional-roundtrip.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @__Sizable__Widget__vtable = internal constant { ptr } { ptr @__thunk_Widget_Sizable_size }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1

examples/expected/0904-optionals-any-to-string-optional.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/1004-errors-try.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/1006-errors-inferred-error-sets.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.127 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/1009-errors-catch.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.126 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/1159-diagnostics-array-const-mixed-elements.exit

@@ -0,0 +1 @@
+1

examples/expected/1159-diagnostics-array-const-mixed-elements.stderr

@@ -0,0 +1,11 @@
+error: constant 'BAD' mixes incompatible element types — annotate the array type
+  --> examples/1159-diagnostics-array-const-mixed-elements.sx:8:19
+   |
+ 8 | BAD :: .["alpha", 1];
+   |                   ^
+
+error: unresolved 'BAD' (in examples/1159-diagnostics-array-const-mixed-elements.sx fn main)
+  --> examples/1159-diagnostics-array-const-mixed-elements.sx:11:19
+   |
+11 |     print("{}\n", BAD[0]);
+   |                   ^^^

examples/expected/1159-diagnostics-array-const-mixed-elements.stdout

@@ -0,0 +1 @@
+

examples/expected/1160-diagnostics-array-const-runtime-element.exit

@@ -0,0 +1 @@
+1

examples/expected/1160-diagnostics-array-const-runtime-element.stderr

@@ -0,0 +1,11 @@
+error: constant 'BAD' must be initialized by compile-time constant elements
+  --> examples/1160-diagnostics-array-const-runtime-element.sx:8:16
+   |
+ 8 | BAD : [2]s64 : .[1, f()];
+   |                ^^^^^^^^^
+
+error: unresolved 'BAD' (in examples/1160-diagnostics-array-const-runtime-element.sx fn main)
+  --> examples/1160-diagnostics-array-const-runtime-element.sx:11:19
+   |
+11 |     print("{}\n", BAD[0]);
+   |                   ^^^

examples/expected/1160-diagnostics-array-const-runtime-element.stdout

@@ -0,0 +1 @@
+

examples/expected/1161-diagnostics-array-const-dim-mismatch.exit

@@ -0,0 +1 @@
+1

examples/expected/1161-diagnostics-array-const-dim-mismatch.stderr

@@ -0,0 +1,11 @@
+error: constant 'BAD' declares [3] elements but its initializer has 2
+  --> examples/1161-diagnostics-array-const-dim-mismatch.sx:6:16
+   |
+ 6 | BAD : [3]s64 : .[1, 2];
+   |                ^^^^^^^
+
+error: unresolved 'BAD' (in examples/1161-diagnostics-array-const-dim-mismatch.sx fn main)
+  --> examples/1161-diagnostics-array-const-dim-mismatch.sx:9:19
+   |
+ 9 |     print("{}\n", BAD[0]);
+   |                   ^^^

examples/expected/1161-diagnostics-array-const-dim-mismatch.stdout

@@ -0,0 +1 @@
+

examples/expected/1202-ffi-cc-c-large-aggregate.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 
 ; Function Attrs: nounwind
 declare void @out(ptr) #0

examples/expected/1309-ffi-objc-class-method-lowering.ir

@@ -1,8 +1,8 @@
 
 @__SxFoo_state_ivar = internal global ptr null
 @__SxFoo_class = internal global ptr null
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
-@__sx_objc_cstr_dealloc = internal global [8 x i8] c"dealloc\00"
+@__sx_objc_cstr_dealloc = internal constant [8 x i8] c"dealloc\00"
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.162 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.163 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1314-ffi-objc-class-dealloc-roundtrip.ir

@@ -1,8 +1,8 @@
 
 @__SxFoo_state_ivar = internal global ptr null
 @__SxFoo_class = internal global ptr null
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
-@__sx_objc_cstr_dealloc = internal global [8 x i8] c"dealloc\00"
+@__sx_objc_cstr_dealloc = internal constant [8 x i8] c"dealloc\00"
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.162 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.163 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1319-ffi-objc-property-sx-defined.ir

@@ -1,7 +1,7 @@
 
 @__SxBox_state_ivar = internal global ptr null
 @__SxBox_class = internal global ptr null
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @OBJC_CLASSLIST_REFERENCES_SxBox = internal global ptr null
 @OBJC_SELECTOR_REFERENCES_init = internal global ptr null
 @OBJC_SELECTOR_REFERENCES_setWidth_ = internal global ptr null
@@ -9,7 +9,7 @@
 @OBJC_SELECTOR_REFERENCES_width = internal global ptr null
 @OBJC_SELECTOR_REFERENCES_height = internal global ptr null
 @OBJC_SELECTOR_REFERENCES_area = internal global ptr null
-@__sx_objc_cstr_dealloc = internal global [8 x i8] c"dealloc\00"
+@__sx_objc_cstr_dealloc = internal constant [8 x i8] c"dealloc\00"
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.162 = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.163 = private unnamed_addr constant [5 x i8] c"true\00", align 1

examples/expected/1329-ffi-objc-call-03-selector-sharing.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @OBJC_SELECTOR_REFERENCES_init = internal global ptr null
 @OBJC_SELECTOR_REFERENCES_release = internal global ptr null
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1

examples/expected/1332-ffi-objc-call-06-sret-return.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @OBJC_SELECTOR_REFERENCES_tripleValue = internal global ptr null
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.162 = private unnamed_addr constant [2 x i8] c"0\00", align 1

examples/expected/1347-ffi-objc-dsl-07-mangling-table.ir

@@ -1,5 +1,5 @@
 
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @OBJC_SELECTOR_REFERENCES_length = internal global ptr null
 @OBJC_SELECTOR_REFERENCES_addObject_ = internal global ptr null
 @OBJC_SELECTOR_REFERENCES_combine_and_ = internal global ptr null

examples/expected/1402-ffi-jni-call-03-methodid-sharing.ir

@@ -1,6 +1,6 @@
 
 @g_should_call = internal global i1 false
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.126 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1403-ffi-jni-call-04-jint-return.ir

@@ -1,6 +1,6 @@
 
 @g_should_call = internal global i1 false
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.126 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1404-ffi-jni-call-05-jlong-return.ir

@@ -1,6 +1,6 @@
 
 @g_should_call = internal global i1 false
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.126 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1405-ffi-jni-call-06-jdouble-return.ir

@@ -1,6 +1,6 @@
 
 @g_should_call = internal global i1 false
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.126 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1406-ffi-jni-call-07-jboolean-return.ir

@@ -1,6 +1,6 @@
 
 @g_should_call = internal global i1 false
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.126 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1407-ffi-jni-call-08-jobject-return.ir

@@ -1,6 +1,6 @@
 
 @g_should_call = internal global i1 false
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.126 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1408-ffi-jni-call-09-static.ir

@@ -1,6 +1,6 @@
 
 @g_should_call = internal global i1 false
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.126 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1418-ffi-jni-class-08-call.ir

@@ -1,6 +1,6 @@
 
 @g_should_call = internal global i1 false
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.126 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1421-ffi-jni-env-02-lexical-direct.ir

@@ -1,6 +1,6 @@
 
 @g_should_call = internal global i1 false
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [2 x i8] c"0\00", align 1
 @str.125 = private unnamed_addr constant [15 x i8] c"result := \22\22; \00", align 1
 @str.126 = private unnamed_addr constant [37 x i8] c"result = concat(result, substr(fmt, \00", align 1

examples/expected/1425-ffi-jni-main-03-ctor.ir

@@ -1,6 +1,6 @@
 
 @g_held_view = internal global ptr null
-@__sx_default_context = internal global { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
+@__sx_default_context = internal constant { { ptr, ptr, ptr }, ptr } { { ptr, ptr, ptr } { ptr null, ptr @__thunk_CAllocator_Allocator_alloc, ptr @__thunk_CAllocator_Allocator_dealloc }, ptr null }
 @str = private unnamed_addr constant [9 x i8] c"onCreate\00", align 1
 @str.162 = private unnamed_addr constant [23 x i8] c"(Landroid/os/Bundle;)V\00", align 1
 @jni.parent.path = private unnamed_addr constant [21 x i8] c"android/app/Activity\00", align 1

src/ir/emit_llvm.zig

@@ -962,6 +962,8 @@ pub const LLVMEmitter = struct {
                 c.LLVMSetInitializer(llvm_global, c.LLVMConstNull(llvm_ty));
             }
 
+            if (global.is_const) c.LLVMSetGlobalConstant(llvm_global, 1);
+
             self.global_map.put(@intCast(i), llvm_global) catch {};
         }
     }

src/ir/lower.zig

@@ -1587,6 +1587,8 @@ pub const Lowering = struct {
     pub const fnPtrTypeWantsCtx = lower_decl.fnPtrTypeWantsCtx;
     pub const scanDecls = lower_decl.scanDecls;
     pub const registerTypedModuleConst = lower_decl.registerTypedModuleConst;
+    pub const registerConstArrayGlobal = lower_decl.registerConstArrayGlobal;
+    pub const inferConstArrayType = lower_decl.inferConstArrayType;
     pub const typedConstInitFits = lower_decl.typedConstInitFits;
     pub const constExprInitFits = lower_decl.constExprInitFits;
     pub const registerTopLevelGlobal = lower_decl.registerTopLevelGlobal;

src/ir/lower/comptime.zig

@@ -50,7 +50,12 @@ pub fn constArrayLiteral(self: *Lowering, elements: []const *const Node, array_t
 /// expression is not constant-foldable here.
 pub fn constExprValue(self: *Lowering, expr: *const Node, expected_ty: TypeId) ?inst_mod.ConstantValue {
     return switch (expr.data) {
-        .int_literal => |il| .{ .int = il.value },
+        // An int element in a FLOAT destination converts exactly (the
+        // int+float promotion rule, element-wise — `[2]f64 : .[1, 2.5]`).
+        .int_literal => |il| if (isFloat(expected_ty))
+            .{ .float = @floatFromInt(il.value) }
+        else
+            .{ .int = il.value },
         .bool_literal => |bl| .{ .boolean = bl.value },
         // A float into an INTEGER destination follows the implicit
         // narrowing rule: an integral float folds to its int, a
@@ -71,7 +76,10 @@ pub fn constExprValue(self: *Lowering, expr: *const Node, expected_ty: TypeId) ?
         .null_literal => .null_val,
         .unary_op => |uo| switch (uo.op) {
             .negate => switch (uo.operand.data) {
-                .int_literal => |il| .{ .int = -il.value },
+                .int_literal => |il| if (isFloat(expected_ty))
+                    .{ .float = @floatFromInt(-il.value) }
+                else
+                    .{ .int = -il.value },
                 .float_literal => |fl| .{ .float = -fl.value },
                 else => null,
             },

src/ir/lower/decl.zig

@@ -778,7 +778,10 @@ pub fn scanDecls(self: *Lowering, decls: []const *const Node) void {
         self.setCurrentSourceFile(decl.source_file);
         switch (decl.data) {
             .var_decl => self.registerTopLevelGlobal(&decl.data.var_decl),
-            .const_decl => |cd| self.registerTypedModuleConst(&cd),
+            .const_decl => |cd| if (cd.value.data == .array_literal)
+                self.registerConstArrayGlobal(&cd)
+            else
+                self.registerTypedModuleConst(&cd),
             else => {},
         }
     }
@@ -924,6 +927,95 @@ pub fn constExprInitFits(self: *Lowering, init_ty: TypeId, dst_ty: TypeId) bool
     return init_ty == dst_ty;
 }
 
+/// Register an array-typed `::` constant (`K : [4]s64 : .[...]`, or the
+/// untyped `A :: .[1, 2, 3]`) as an IMMUTABLE module global: one storage,
+/// reads GEP it, the emitter marks it LLVMSetGlobalConstant, dead-global
+/// elimination drops it when unused. Source-aware reads come for free via
+/// `selectGlobalAuthor` (the per-source partition is written here).
+pub fn registerConstArrayGlobal(self: *Lowering, cd: *const ast.ConstDecl) void {
+    const al = &cd.value.data.array_literal;
+    const arr_ty: TypeId = blk: {
+        if (cd.type_annotation) |ta| {
+            const t = self.resolveType(ta);
+            if (t == .unresolved) return; // annotation already diagnosed
+            if (t.isBuiltin() or self.module.types.get(t) != .array) {
+                if (self.diagnostics) |d|
+                    d.addFmt(.err, cd.value.span, "constant '{s}' has an array-literal initializer but its annotation is not an array type", .{cd.name});
+                return;
+            }
+            const dim = self.module.types.get(t).array.length;
+            if (dim != al.elements.len) {
+                if (self.diagnostics) |d|
+                    d.addFmt(.err, cd.value.span, "constant '{s}' declares [{d}] elements but its initializer has {d}", .{ cd.name, dim, al.elements.len });
+                return;
+            }
+            break :blk t;
+        }
+        break :blk self.inferConstArrayType(cd.name, al.elements, cd.value.span) orelse return;
+    };
+    const init_val = self.constArrayLiteral(al.elements, arr_ty) orelse {
+        if (self.diagnostics) |d|
+            d.addFmt(.err, cd.value.span, "constant '{s}' must be initialized by compile-time constant elements", .{cd.name});
+        return;
+    };
+    const name_id = self.module.types.internString(cd.name);
+    const gid = self.module.addGlobal(.{
+        .name = name_id,
+        .ty = arr_ty,
+        .init_val = init_val,
+        .is_const = true,
+    });
+    self.putGlobal(self.current_source_file, cd.name, .{ .id = gid, .ty = arr_ty });
+}
+
+/// Infer `[N]T` for an untyped array-literal constant. Element types unify:
+/// all ints → s64; ANY float promotes the element type to f64 (ints convert
+/// exactly — the int+float promotion rule for consts, element-wise); bool /
+/// string homogeneous only. A non-numeric mix or a non-inferable element
+/// shape (nested aggregate, enum literal, named const) asks for an
+/// annotation rather than guessing.
+pub fn inferConstArrayType(self: *Lowering, name: []const u8, elements: []const *const Node, span: ast.Span) ?TypeId {
+    if (elements.len == 0) {
+        if (self.diagnostics) |d|
+            d.addFmt(.err, span, "constant '{s}' is an empty array literal — annotate the type (e.g. `{s} : [0]s64 : .[]`)", .{ name, name });
+        return null;
+    }
+    var elem_ty: ?TypeId = null;
+    for (elements) |e| {
+        const leaf: ?TypeId = switch (e.data) {
+            .int_literal => .s64,
+            .float_literal => .f64,
+            .bool_literal => .bool,
+            .string_literal => .string,
+            .unary_op => |uo| if (uo.op == .negate) switch (uo.operand.data) {
+                .int_literal => .s64,
+                .float_literal => .f64,
+                else => null,
+            } else null,
+            else => null,
+        };
+        const lt = leaf orelse {
+            if (self.diagnostics) |d|
+                d.addFmt(.err, e.span, "cannot infer the element type of constant '{s}' from this element — annotate the array type", .{name});
+            return null;
+        };
+        if (elem_ty) |prev| {
+            if (prev == lt) continue;
+            // Numeric mix promotes to the float element type.
+            const numeric_pair = (prev == .s64 and lt == .f64) or (prev == .f64 and lt == .s64);
+            if (numeric_pair) {
+                elem_ty = .f64;
+                continue;
+            }
+            if (self.diagnostics) |d|
+                d.addFmt(.err, e.span, "constant '{s}' mixes incompatible element types — annotate the array type", .{name});
+            return null;
+        }
+        elem_ty = lt;
+    }
+    return self.module.types.arrayOf(elem_ty.?, @intCast(elements.len));
+}
+
 /// Register a top-level mutable global (e.g., `context : Context = ---;`).
 /// Run AFTER `resolveForwardIdentifierAliases` so a forward identifier alias
 /// in the type annotation (`A :: B; B :: s32; g : A = 7;`) resolves to its