Commit 152a2ceaf7

mlugg <mlugg@mlugg.co.uk>
2024-03-26 04:56:54
compiler: audit uses of `ptr.addr` in the frontend
This commit also performs some refactors to `TypedValue.print` in preparation for improved comptime pointer access logic. Once that logic exists, `TypedValue.print` can use Sema to access pointers for more helpful printing. This commit also implements proposal #19435, because the existing logic there relied on some blatantly incorrect code in `Value.sliceLen`. Resolves: #19435
1 parent 884d957
Changed files (4)
src/Sema.zig
@@ -1881,10 +1881,10 @@ pub fn toConstString(
     air_inst: Air.Inst.Ref,
     reason: NeededComptimeReason,
 ) ![]u8 {
-    const wanted_type = Type.slice_const_u8;
-    const coerced_inst = try sema.coerce(block, wanted_type, air_inst, src);
-    const val = try sema.resolveConstDefinedValue(block, src, coerced_inst, reason);
-    return val.toAllocatedBytes(wanted_type, sema.arena, sema.mod);
+    const coerced_inst = try sema.coerce(block, Type.slice_const_u8, air_inst, src);
+    const slice_val = try sema.resolveConstDefinedValue(block, src, coerced_inst, reason);
+    const arr_val = try sema.derefSliceAsArray(block, src, slice_val, reason);
+    return arr_val.toAllocatedBytes(arr_val.typeOf(sema.mod), sema.arena, sema.mod);
 }
 
 pub fn resolveConstStringIntern(
@@ -14498,12 +14498,16 @@ fn zirArrayCat(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
             else => unreachable,
         }) |rhs_val| {
             const lhs_sub_val = if (lhs_ty.isSinglePointer(mod))
-                (try sema.pointerDeref(block, lhs_src, lhs_val, lhs_ty)).?
+                try sema.pointerDeref(block, lhs_src, lhs_val, lhs_ty) orelse break :rs lhs_src
+            else if (lhs_ty.isSlice(mod))
+                try sema.maybeDerefSliceAsArray(block, lhs_src, lhs_val) orelse break :rs lhs_src
             else
                 lhs_val;
 
             const rhs_sub_val = if (rhs_ty.isSinglePointer(mod))
-                (try sema.pointerDeref(block, rhs_src, rhs_val, rhs_ty)).?
+                try sema.pointerDeref(block, rhs_src, rhs_val, rhs_ty) orelse break :rs rhs_src
+            else if (rhs_ty.isSlice(mod))
+                try sema.maybeDerefSliceAsArray(block, rhs_src, rhs_val) orelse break :rs rhs_src
             else
                 rhs_val;
 
@@ -14623,10 +14627,7 @@ fn getArrayCatInfo(sema: *Sema, block: *Block, src: LazySrcLoc, operand: Air.Ins
         .Pointer => {
             const ptr_info = operand_ty.ptrInfo(mod);
             switch (ptr_info.flags.size) {
-                // TODO: in the Many case here this should only work if the type
-                // has a sentinel, and this code should compute the length based
-                // on the sentinel value.
-                .Slice, .Many => {
+                .Slice => {
                     const val = try sema.resolveConstDefinedValue(block, src, operand, .{
                         .needed_comptime_reason = "slice value being concatenated must be comptime-known",
                     });
@@ -14636,7 +14637,7 @@ fn getArrayCatInfo(sema: *Sema, block: *Block, src: LazySrcLoc, operand: Air.Ins
                             .none => null,
                             else => Value.fromInterned(ptr_info.sentinel),
                         },
-                        .len = val.sliceLen(mod),
+                        .len = try val.sliceLen(sema),
                     };
                 },
                 .One => {
@@ -14644,7 +14645,7 @@ fn getArrayCatInfo(sema: *Sema, block: *Block, src: LazySrcLoc, operand: Air.Ins
                         return Type.fromInterned(ptr_info.child).arrayInfo(mod);
                     }
                 },
-                .C => {},
+                .C, .Many => {},
             }
         },
         .Struct => {
@@ -14830,9 +14831,11 @@ fn zirArrayMul(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
     const ptr_addrspace = if (lhs_ty.zigTypeTag(mod) == .Pointer) lhs_ty.ptrAddressSpace(mod) else null;
     const lhs_len = try sema.usizeCast(block, lhs_src, lhs_info.len);
 
-    if (try sema.resolveDefinedValue(block, lhs_src, lhs)) |lhs_val| {
+    if (try sema.resolveDefinedValue(block, lhs_src, lhs)) |lhs_val| ct: {
         const lhs_sub_val = if (lhs_ty.isSinglePointer(mod))
-            (try sema.pointerDeref(block, lhs_src, lhs_val, lhs_ty)).?
+            try sema.pointerDeref(block, lhs_src, lhs_val, lhs_ty) orelse break :ct
+        else if (lhs_ty.isSlice(mod))
+            try sema.maybeDerefSliceAsArray(block, lhs_src, lhs_val) orelse break :ct
         else
             lhs_val;
 
@@ -14840,7 +14843,7 @@ fn zirArrayMul(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
             // Optimization for the common pattern of a single element repeated N times, such
             // as zero-filling a byte array.
             if (lhs_len == 1 and lhs_info.sentinel == null) {
-                const elem_val = (try lhs_sub_val.maybeElemValueFull(sema, mod, 0)).?;
+                const elem_val = try lhs_sub_val.elemValue(mod, 0);
                 break :v try mod.intern(.{ .aggregate = .{
                     .ty = result_ty.toIntern(),
                     .storage = .{ .repeated_elem = elem_val.toIntern() },
@@ -14852,7 +14855,7 @@ fn zirArrayMul(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
             while (elem_i < result_len) {
                 var lhs_i: usize = 0;
                 while (lhs_i < lhs_len) : (lhs_i += 1) {
-                    const elem_val = (try lhs_sub_val.maybeElemValueFull(sema, mod, lhs_i)).?;
+                    const elem_val = try lhs_sub_val.elemValue(mod, lhs_i);
                     element_vals[elem_i] = elem_val.toIntern();
                     elem_i += 1;
                 }
@@ -21124,7 +21127,9 @@ fn zirReify(
         .needed_comptime_reason = "operand to @Type must be comptime-known",
     });
     const union_val = ip.indexToKey(val.toIntern()).un;
-    if (try sema.anyUndef(Value.fromInterned(union_val.val))) return sema.failWithUseOfUndef(block, src);
+    if (try sema.anyUndef(block, operand_src, Value.fromInterned(union_val.val))) {
+        return sema.failWithUseOfUndef(block, operand_src);
+    }
     const tag_index = type_info_ty.unionTagFieldIndex(Value.fromInterned(union_val.tag), mod).?;
     switch (@as(std.builtin.TypeId, @enumFromInt(tag_index))) {
         .Type => return .type_type,
@@ -21365,11 +21370,15 @@ fn zirReify(
             const payload_val = Value.fromInterned(union_val.val).optionalValue(mod) orelse
                 return Air.internedToRef(Type.anyerror.toIntern());
 
-            const len = try sema.usizeCast(block, src, payload_val.sliceLen(mod));
+            const names_val = try sema.derefSliceAsArray(block, src, payload_val, .{
+                .needed_comptime_reason = "error set contents must be comptime-known",
+            });
+
+            const len = try sema.usizeCast(block, src, names_val.typeOf(mod).arrayLen(mod));
             var names: InferredErrorSet.NameMap = .{};
             try names.ensureUnusedCapacity(sema.arena, len);
             for (0..len) |i| {
-                const elem_val = (try payload_val.maybeElemValueFull(sema, mod, i)).?;
+                const elem_val = try names_val.elemValue(mod, i);
                 const elem_struct_type = ip.loadStructType(ip.typeOf(elem_val.toIntern()));
                 const name_val = try elem_val.fieldValue(mod, elem_struct_type.nameIndex(
                     ip,
@@ -21417,7 +21426,7 @@ fn zirReify(
             const layout = mod.toEnum(std.builtin.Type.ContainerLayout, layout_val);
 
             // Decls
-            if (decls_val.sliceLen(mod) > 0) {
+            if (try decls_val.sliceLen(sema) > 0) {
                 return sema.fail(block, src, "reified structs must have no decls", .{});
             }
 
@@ -21425,7 +21434,11 @@ fn zirReify(
                 return sema.fail(block, src, "non-packed struct does not support backing integer type", .{});
             }
 
-            return try sema.reifyStruct(block, inst, src, layout, backing_integer_val, fields_val, name_strategy, is_tuple_val.toBool());
+            const fields_arr = try sema.derefSliceAsArray(block, operand_src, fields_val, .{
+                .needed_comptime_reason = "struct fields must be comptime-known",
+            });
+
+            return try sema.reifyStruct(block, inst, src, layout, backing_integer_val, fields_arr, name_strategy, is_tuple_val.toBool());
         },
         .Enum => {
             const struct_type = ip.loadStructType(ip.typeOf(union_val.val));
@@ -21446,11 +21459,15 @@ fn zirReify(
                 try ip.getOrPutString(gpa, "is_exhaustive"),
             ).?);
 
-            if (decls_val.sliceLen(mod) > 0) {
+            if (try decls_val.sliceLen(sema) > 0) {
                 return sema.fail(block, src, "reified enums must have no decls", .{});
             }
 
-            return sema.reifyEnum(block, inst, src, tag_type_val.toType(), is_exhaustive_val.toBool(), fields_val, name_strategy);
+            const fields_arr = try sema.derefSliceAsArray(block, operand_src, fields_val, .{
+                .needed_comptime_reason = "enum fields must be comptime-known",
+            });
+
+            return sema.reifyEnum(block, inst, src, tag_type_val.toType(), is_exhaustive_val.toBool(), fields_arr, name_strategy);
         },
         .Opaque => {
             const struct_type = ip.loadStructType(ip.typeOf(union_val.val));
@@ -21460,7 +21477,7 @@ fn zirReify(
             ).?);
 
             // Decls
-            if (decls_val.sliceLen(mod) > 0) {
+            if (try decls_val.sliceLen(sema) > 0) {
                 return sema.fail(block, src, "reified opaque must have no decls", .{});
             }
 
@@ -21505,12 +21522,16 @@ fn zirReify(
                 try ip.getOrPutString(gpa, "decls"),
             ).?);
 
-            if (decls_val.sliceLen(mod) > 0) {
+            if (try decls_val.sliceLen(sema) > 0) {
                 return sema.fail(block, src, "reified unions must have no decls", .{});
             }
             const layout = mod.toEnum(std.builtin.Type.ContainerLayout, layout_val);
 
-            return sema.reifyUnion(block, inst, src, layout, tag_type_val, fields_val, name_strategy);
+            const fields_arr = try sema.derefSliceAsArray(block, operand_src, fields_val, .{
+                .needed_comptime_reason = "union fields must be comptime-known",
+            });
+
+            return sema.reifyUnion(block, inst, src, layout, tag_type_val, fields_arr, name_strategy);
         },
         .Fn => {
             const struct_type = ip.loadStructType(ip.typeOf(union_val.val));
@@ -21530,7 +21551,7 @@ fn zirReify(
                 ip,
                 try ip.getOrPutString(gpa, "return_type"),
             ).?);
-            const params_val = try Value.fromInterned(union_val.val).fieldValue(mod, struct_type.nameIndex(
+            const params_slice_val = try Value.fromInterned(union_val.val).fieldValue(mod, struct_type.nameIndex(
                 ip,
                 try ip.getOrPutString(gpa, "params"),
             ).?);
@@ -21549,12 +21570,16 @@ fn zirReify(
             const return_type = return_type_val.optionalValue(mod) orelse
                 return sema.fail(block, src, "Type.Fn.return_type must be non-null for @Type", .{});
 
-            const args_len = try sema.usizeCast(block, src, params_val.sliceLen(mod));
+            const params_val = try sema.derefSliceAsArray(block, operand_src, params_slice_val, .{
+                .needed_comptime_reason = "function parameters must be comptime-known",
+            });
+
+            const args_len = try sema.usizeCast(block, src, params_val.typeOf(mod).arrayLen(mod));
             const param_types = try sema.arena.alloc(InternPool.Index, args_len);
 
             var noalias_bits: u32 = 0;
             for (param_types, 0..) |*param_type, i| {
-                const elem_val = (try params_val.maybeElemValueFull(sema, mod, i)).?;
+                const elem_val = try params_val.elemValue(mod, i);
                 const elem_struct_type = ip.loadStructType(ip.typeOf(elem_val.toIntern()));
                 const param_is_generic_val = try elem_val.fieldValue(mod, elem_struct_type.nameIndex(
                     ip,
@@ -21615,7 +21640,7 @@ fn reifyEnum(
 
     // This logic must stay in sync with the structure of `std.builtin.Type.Enum` - search for `fieldValue`.
 
-    const fields_len: u32 = @intCast(fields_val.sliceLen(mod));
+    const fields_len: u32 = @intCast(fields_val.typeOf(mod).arrayLen(mod));
 
     // The validation work here is non-trivial, and it's possible the type already exists.
     // So in this first pass, let's just construct a hash to optimize for this case. If the
@@ -21629,7 +21654,7 @@ fn reifyEnum(
     std.hash.autoHash(&hasher, fields_len);
 
     for (0..fields_len) |field_idx| {
-        const field_info = (try fields_val.maybeElemValueFull(sema, mod, field_idx)).?;
+        const field_info = try fields_val.elemValue(mod, field_idx);
 
         const field_name_val = try field_info.fieldValue(mod, 0);
         const field_value_val = try sema.resolveLazyValue(try field_info.fieldValue(mod, 1));
@@ -21674,7 +21699,7 @@ fn reifyEnum(
     wip_ty.setTagTy(ip, tag_ty.toIntern());
 
     for (0..fields_len) |field_idx| {
-        const field_info = (try fields_val.maybeElemValueFull(sema, mod, field_idx)).?;
+        const field_info = try fields_val.elemValue(mod, field_idx);
 
         const field_name_val = try field_info.fieldValue(mod, 0);
         const field_value_val = try sema.resolveLazyValue(try field_info.fieldValue(mod, 1));
@@ -21736,7 +21761,7 @@ fn reifyUnion(
 
     // This logic must stay in sync with the structure of `std.builtin.Type.Union` - search for `fieldValue`.
 
-    const fields_len: u32 = @intCast(fields_val.sliceLen(mod));
+    const fields_len: u32 = @intCast(fields_val.typeOf(mod).arrayLen(mod));
 
     // The validation work here is non-trivial, and it's possible the type already exists.
     // So in this first pass, let's just construct a hash to optimize for this case. If the
@@ -21752,7 +21777,7 @@ fn reifyUnion(
     var any_aligns = false;
 
     for (0..fields_len) |field_idx| {
-        const field_info = (try fields_val.maybeElemValueFull(sema, mod, field_idx)).?;
+        const field_info = try fields_val.elemValue(mod, field_idx);
 
         const field_name_val = try field_info.fieldValue(mod, 0);
         const field_type_val = try field_info.fieldValue(mod, 1);
@@ -21828,7 +21853,7 @@ fn reifyUnion(
         var seen_tags = try std.DynamicBitSetUnmanaged.initEmpty(sema.arena, tag_ty_fields_len);
 
         for (field_types, 0..) |*field_ty, field_idx| {
-            const field_info = (try fields_val.maybeElemValueFull(sema, mod, field_idx)).?;
+            const field_info = try fields_val.elemValue(mod, field_idx);
 
             const field_name_val = try field_info.fieldValue(mod, 0);
             const field_type_val = try field_info.fieldValue(mod, 1);
@@ -21880,7 +21905,7 @@ fn reifyUnion(
         try field_names.ensureTotalCapacity(sema.arena, fields_len);
 
         for (field_types, 0..) |*field_ty, field_idx| {
-            const field_info = (try fields_val.maybeElemValueFull(sema, mod, field_idx)).?;
+            const field_info = try fields_val.elemValue(mod, field_idx);
 
             const field_name_val = try field_info.fieldValue(mod, 0);
             const field_type_val = try field_info.fieldValue(mod, 1);
@@ -21974,7 +21999,7 @@ fn reifyStruct(
 
     // This logic must stay in sync with the structure of `std.builtin.Type.Struct` - search for `fieldValue`.
 
-    const fields_len: u32 = @intCast(fields_val.sliceLen(mod));
+    const fields_len: u32 = @intCast(fields_val.typeOf(mod).arrayLen(mod));
 
     // The validation work here is non-trivial, and it's possible the type already exists.
     // So in this first pass, let's just construct a hash to optimize for this case. If the
@@ -21993,7 +22018,7 @@ fn reifyStruct(
     var any_aligned_fields = false;
 
     for (0..fields_len) |field_idx| {
-        const field_info = (try fields_val.maybeElemValueFull(sema, mod, field_idx)).?;
+        const field_info = try fields_val.elemValue(mod, field_idx);
 
         const field_name_val = try field_info.fieldValue(mod, 0);
         const field_type_val = try field_info.fieldValue(mod, 1);
@@ -22071,7 +22096,7 @@ fn reifyStruct(
     const struct_type = ip.loadStructType(wip_ty.index);
 
     for (0..fields_len) |field_idx| {
-        const field_info = (try fields_val.maybeElemValueFull(sema, mod, field_idx)).?;
+        const field_info = try fields_val.elemValue(mod, field_idx);
 
         const field_name_val = try field_info.fieldValue(mod, 0);
         const field_type_val = try field_info.fieldValue(mod, 1);
@@ -23892,11 +23917,9 @@ fn resolveExportOptions(
     const visibility_src = sema.maybeOptionsSrc(block, src, "visibility");
 
     const name_operand = try sema.fieldVal(block, src, options, try ip.getOrPutString(gpa, "name"), name_src);
-    const name_val = try sema.resolveConstDefinedValue(block, name_src, name_operand, .{
+    const name = try sema.toConstString(block, name_src, name_operand, .{
         .needed_comptime_reason = "name of exported value must be comptime-known",
     });
-    const name_ty = Type.slice_const_u8;
-    const name = try name_val.toAllocatedBytes(name_ty, sema.arena, mod);
 
     const linkage_operand = try sema.fieldVal(block, src, options, try ip.getOrPutString(gpa, "linkage"), linkage_src);
     const linkage_val = try sema.resolveConstDefinedValue(block, linkage_src, linkage_operand, .{
@@ -23908,9 +23931,10 @@ fn resolveExportOptions(
     const section_opt_val = try sema.resolveConstDefinedValue(block, section_src, section_operand, .{
         .needed_comptime_reason = "linksection of exported value must be comptime-known",
     });
-    const section_ty = Type.slice_const_u8;
     const section = if (section_opt_val.optionalValue(mod)) |section_val|
-        try section_val.toAllocatedBytes(section_ty, sema.arena, mod)
+        try sema.toConstString(block, section_src, Air.internedToRef(section_val.toIntern()), .{
+            .needed_comptime_reason = "linksection of exported value must be comptime-known",
+        })
     else
         null;
 
@@ -26028,10 +26052,9 @@ fn resolveExternOptions(
     const thread_local_src = sema.maybeOptionsSrc(block, src, "thread_local");
 
     const name_ref = try sema.fieldVal(block, src, options, try ip.getOrPutString(gpa, "name"), name_src);
-    const name_val = try sema.resolveConstDefinedValue(block, name_src, name_ref, .{
+    const name = try sema.toConstString(block, name_src, name_ref, .{
         .needed_comptime_reason = "name of the extern symbol must be comptime-known",
     });
-    const name = try name_val.toAllocatedBytes(Type.slice_const_u8, sema.arena, mod);
 
     const library_name_inst = try sema.fieldVal(block, src, options, try ip.getOrPutString(gpa, "library_name"), library_src);
     const library_name_val = try sema.resolveConstDefinedValue(block, library_src, library_name_inst, .{
@@ -26050,7 +26073,9 @@ fn resolveExternOptions(
     });
 
     const library_name = if (library_name_val.optionalValue(mod)) |library_name_payload| library_name: {
-        const library_name = try library_name_payload.toAllocatedBytes(Type.slice_const_u8, sema.arena, mod);
+        const library_name = try sema.toConstString(block, library_src, Air.internedToRef(library_name_payload.toIntern()), .{
+            .needed_comptime_reason = "library in which extern symbol is must be comptime-known",
+        });
         if (library_name.len == 0) {
             return sema.fail(block, library_src, "library name cannot be empty", .{});
         }
@@ -28564,7 +28589,7 @@ fn elemValSlice(
 
     if (maybe_slice_val) |slice_val| {
         runtime_src = elem_index_src;
-        const slice_len = slice_val.sliceLen(mod);
+        const slice_len = try slice_val.sliceLen(sema);
         const slice_len_s = slice_len + @intFromBool(slice_sent);
         if (slice_len_s == 0) {
             return sema.fail(block, slice_src, "indexing into empty slice is not allowed", .{});
@@ -28589,7 +28614,7 @@ fn elemValSlice(
     try sema.requireRuntimeBlock(block, src, runtime_src);
     if (oob_safety and block.wantSafety()) {
         const len_inst = if (maybe_slice_val) |slice_val|
-            try mod.intRef(Type.usize, slice_val.sliceLen(mod))
+            try mod.intRef(Type.usize, try slice_val.sliceLen(sema))
         else
             try block.addTyOp(.slice_len, Type.usize, slice);
         const cmp_op: Air.Inst.Tag = if (slice_sent) .cmp_lte else .cmp_lt;
@@ -28626,7 +28651,7 @@ fn elemPtrSlice(
         if (slice_val.isUndef(mod)) {
             return mod.undefRef(elem_ptr_ty);
         }
-        const slice_len = slice_val.sliceLen(mod);
+        const slice_len = try slice_val.sliceLen(sema);
         const slice_len_s = slice_len + @intFromBool(slice_sent);
         if (slice_len_s == 0) {
             return sema.fail(block, slice_src, "indexing into empty slice is not allowed", .{});
@@ -28649,7 +28674,7 @@ fn elemPtrSlice(
         const len_inst = len: {
             if (maybe_undef_slice_val) |slice_val|
                 if (!slice_val.isUndef(mod))
-                    break :len try mod.intRef(Type.usize, slice_val.sliceLen(mod));
+                    break :len try mod.intRef(Type.usize, try slice_val.sliceLen(sema));
             break :len try block.addTyOp(.slice_len, Type.usize, slice);
         };
         const cmp_op: Air.Inst.Tag = if (slice_sent) .cmp_lte else .cmp_lt;
@@ -31523,16 +31548,11 @@ fn coerceArrayPtrToSlice(
     if (try sema.resolveValue(inst)) |val| {
         const ptr_array_ty = sema.typeOf(inst);
         const array_ty = ptr_array_ty.childType(mod);
+        const slice_ptr_ty = dest_ty.slicePtrFieldType(mod);
+        const slice_ptr = try mod.getCoerced(val, slice_ptr_ty);
         const slice_val = try mod.intern(.{ .slice = .{
             .ty = dest_ty.toIntern(),
-            .ptr = try mod.intern(.{ .ptr = .{
-                .ty = dest_ty.slicePtrFieldType(mod).toIntern(),
-                .addr = switch (mod.intern_pool.indexToKey(val.toIntern())) {
-                    .undef => .{ .int = try mod.intern(.{ .undef = .usize_type }) },
-                    .ptr => |ptr| ptr.addr,
-                    else => unreachable,
-                },
-            } }),
+            .ptr = slice_ptr.toIntern(),
             .len = (try mod.intValue(Type.usize, array_ty.arrayLen(mod))).toIntern(),
         } });
         return Air.internedToRef(slice_val);
@@ -32602,7 +32622,7 @@ fn analyzeSliceLen(
         if (slice_val.isUndef(mod)) {
             return mod.undefRef(Type.usize);
         }
-        return mod.intRef(Type.usize, slice_val.sliceLen(sema.mod));
+        return mod.intRef(Type.usize, try slice_val.sliceLen(sema));
     }
     try sema.requireRuntimeBlock(block, src, null);
     return block.addTyOp(.slice_len, Type.usize, slice_inst);
@@ -33041,7 +33061,7 @@ fn analyzeSlice(
                             return sema.fail(block, src, "slice of undefined", .{});
                         }
                         const has_sentinel = slice_ty.sentinel(mod) != null;
-                        const slice_len = slice_val.sliceLen(mod);
+                        const slice_len = try slice_val.sliceLen(sema);
                         const len_plus_sent = slice_len + @intFromBool(has_sentinel);
                         const slice_len_val_with_sentinel = try mod.intValue(Type.usize, len_plus_sent);
                         if (!(try sema.compareAll(end_val, .lte, slice_len_val_with_sentinel, Type.usize))) {
@@ -33056,7 +33076,7 @@ fn analyzeSlice(
                                 "end index {} out of bounds for slice of length {d}{s}",
                                 .{
                                     end_val.fmtValue(Type.usize, mod),
-                                    slice_val.sliceLen(mod),
+                                    try slice_val.sliceLen(sema),
                                     sentinel_label,
                                 },
                             );
@@ -33285,7 +33305,7 @@ fn analyzeSlice(
             if (try sema.resolveDefinedValue(block, src, ptr_or_slice)) |slice_val| {
                 // we don't need to add one for sentinels because the
                 // underlying value data includes the sentinel
-                break :blk try mod.intRef(Type.usize, slice_val.sliceLen(mod));
+                break :blk try mod.intRef(Type.usize, try slice_val.sliceLen(sema));
             }
 
             const slice_len_inst = try block.addTyOp(.slice_len, Type.usize, ptr_or_slice);
@@ -39003,22 +39023,22 @@ fn validateRuntimeValue(sema: *Sema, block: *Block, val_src: LazySrcLoc, val: Ai
 }
 
 /// Returns true if any value contained in `val` is undefined.
-fn anyUndef(sema: *Sema, val: Value) !bool {
+fn anyUndef(sema: *Sema, block: *Block, src: LazySrcLoc, val: Value) !bool {
     const mod = sema.mod;
-    return switch (val.toIntern()) {
+    return switch (mod.intern_pool.indexToKey(val.toIntern())) {
         .undef => true,
-        else => switch (mod.intern_pool.indexToKey(val.toIntern())) {
-            .undef => true,
-            .simple_value => |v| v == .undefined,
-            .slice => |slice| for (0..@intCast(Value.fromInterned(slice.len).toUnsignedInt(mod))) |idx| {
-                if (try sema.anyUndef((try val.maybeElemValueFull(sema, mod, idx)).?)) break true;
-            } else false,
-            .aggregate => |aggregate| for (0..aggregate.storage.values().len) |i| {
-                const elem = mod.intern_pool.indexToKey(val.toIntern()).aggregate.storage.values()[i];
-                if (try sema.anyUndef(Value.fromInterned(elem))) break true;
-            } else false,
-            else => false,
-        },
+        .simple_value => |v| v == .undefined,
+        .slice => {
+            // If the slice contents are runtime-known, reification will fail later on with a
+            // specific error message.
+            const arr = try sema.maybeDerefSliceAsArray(block, src, val) orelse return false;
+            return sema.anyUndef(block, src, arr);
+        },
+        .aggregate => |aggregate| for (0..aggregate.storage.values().len) |i| {
+            const elem = mod.intern_pool.indexToKey(val.toIntern()).aggregate.storage.values()[i];
+            if (try sema.anyUndef(block, src, Value.fromInterned(elem))) break true;
+        } else false,
+        else => false,
     };
 }
 
@@ -39050,6 +39070,20 @@ fn derefSliceAsArray(
     slice_val: Value,
     reason: NeededComptimeReason,
 ) CompileError!Value {
+    return try sema.maybeDerefSliceAsArray(block, src, slice_val) orelse {
+        return sema.failWithNeededComptime(block, src, reason);
+    };
+}
+
+/// Given a slice value, attempts to dereference it into a comptime-known array.
+/// Returns `null` if the contents of the slice are not comptime-known.
+/// Asserts that `slice_val` is a slice.
+fn maybeDerefSliceAsArray(
+    sema: *Sema,
+    block: *Block,
+    src: LazySrcLoc,
+    slice_val: Value,
+) CompileError!?Value {
     const zcu = sema.mod;
     const ip = &zcu.intern_pool;
     assert(Type.fromInterned(ip.typeOf(slice_val.toIntern())).isSlice(zcu));
@@ -39072,7 +39106,5 @@ fn derefSliceAsArray(
         break :p p;
     });
     const casted_ptr = try zcu.getCoerced(Value.fromInterned(slice.ptr), ptr_ty);
-    return try sema.pointerDeref(block, src, casted_ptr, ptr_ty) orelse {
-        return sema.failWithNeededComptime(block, src, reason);
-    };
+    return sema.pointerDeref(block, src, casted_ptr, ptr_ty);
 }
src/TypedValue.zig
@@ -1,7 +1,10 @@
 const std = @import("std");
 const Type = @import("type.zig").Type;
 const Value = @import("Value.zig");
-const Module = @import("Module.zig");
+const Zcu = @import("Module.zig");
+const Module = Zcu;
+const Sema = @import("Sema.zig");
+const InternPool = @import("InternPool.zig");
 const Allocator = std.mem.Allocator;
 const TypedValue = @This();
 const Target = std.Target;
@@ -61,8 +64,10 @@ pub fn format(
 ) !void {
     _ = options;
     comptime std.debug.assert(fmt.len == 0);
-    return ctx.tv.print(writer, 3, ctx.mod) catch |err| switch (err) {
+    return ctx.tv.print(writer, 3, ctx.mod, null) catch |err| switch (err) {
         error.OutOfMemory => @panic("OOM"), // We're not allowed to return this from a format function
+        error.ComptimeBreak, error.ComptimeReturn => unreachable,
+        error.AnalysisFail, error.NeededSourceLocation => unreachable, // TODO: re-evaluate when we actually pass `opt_sema`
         else => |e| return e,
     };
 }
@@ -73,11 +78,12 @@ pub fn print(
     writer: anytype,
     level: u8,
     mod: *Module,
-) (@TypeOf(writer).Error || Allocator.Error)!void {
-    var val = tv.val;
-    var ty = tv.ty;
+    /// If this `Sema` is provided, we will recurse through pointers where possible to provide friendly output.
+    opt_sema: ?*Sema,
+) (@TypeOf(writer).Error || Module.CompileError)!void {
     const ip = &mod.intern_pool;
-    while (true) switch (ip.indexToKey(val.toIntern())) {
+    const val = tv.val;
+    switch (ip.indexToKey(val.toIntern())) {
         .int_type,
         .ptr_type,
         .array_type,
@@ -94,324 +100,298 @@ pub fn print(
         .func_type,
         .error_set_type,
         .inferred_error_set_type,
-        => return Type.print(val.toType(), writer, mod),
-        .undef => return writer.writeAll("undefined"),
+        => try Type.print(val.toType(), writer, mod),
+        .undef => try writer.writeAll("undefined"),
         .simple_value => |simple_value| switch (simple_value) {
-            .void => return writer.writeAll("{}"),
-            .empty_struct => return printAggregate(ty, val, writer, level, mod),
-            .generic_poison => return writer.writeAll("(generic poison)"),
-            else => return writer.writeAll(@tagName(simple_value)),
+            .void => try writer.writeAll("{}"),
+            .empty_struct => try writer.writeAll(".{}"),
+            .generic_poison => try writer.writeAll("(generic poison)"),
+            else => try writer.writeAll(@tagName(simple_value)),
         },
-        .variable => return writer.writeAll("(variable)"),
-        .extern_func => |extern_func| return writer.print("(extern function '{}')", .{
+        .variable => try writer.writeAll("(variable)"),
+        .extern_func => |extern_func| try writer.print("(extern function '{}')", .{
             mod.declPtr(extern_func.decl).name.fmt(ip),
         }),
-        .func => |func| return writer.print("(function '{}')", .{
+        .func => |func| try writer.print("(function '{}')", .{
             mod.declPtr(func.owner_decl).name.fmt(ip),
         }),
         .int => |int| switch (int.storage) {
-            inline .u64, .i64, .big_int => |x| return writer.print("{}", .{x}),
-            .lazy_align => |lazy_ty| return writer.print("{d}", .{
-                Type.fromInterned(lazy_ty).abiAlignment(mod),
-            }),
-            .lazy_size => |lazy_ty| return writer.print("{d}", .{
-                Type.fromInterned(lazy_ty).abiSize(mod),
-            }),
+            inline .u64, .i64, .big_int => |x| try writer.print("{}", .{x}),
+            .lazy_align => |ty| if (opt_sema) |sema| {
+                const a = (try Type.fromInterned(ty).abiAlignmentAdvanced(mod, .{ .sema = sema })).scalar;
+                try writer.print("{}", .{a.toByteUnits(0)});
+            } else try writer.print("@alignOf({})", .{Type.fromInterned(ty).fmt(mod)}),
+            .lazy_size => |ty| if (opt_sema) |sema| {
+                const s = (try Type.fromInterned(ty).abiSizeAdvanced(mod, .{ .sema = sema })).scalar;
+                try writer.print("{}", .{s});
+            } else try writer.print("@sizeOf({})", .{Type.fromInterned(ty).fmt(mod)}),
         },
-        .err => |err| return writer.print("error.{}", .{
+        .err => |err| try writer.print("error.{}", .{
             err.name.fmt(ip),
         }),
         .error_union => |error_union| switch (error_union.val) {
-            .err_name => |err_name| return writer.print("error.{}", .{
+            .err_name => |err_name| try writer.print("error.{}", .{
                 err_name.fmt(ip),
             }),
-            .payload => |payload| {
-                val = Value.fromInterned(payload);
-                ty = ty.errorUnionPayload(mod);
-            },
+            .payload => |payload| try print(.{
+                .ty = tv.ty.errorUnionPayload(mod),
+                .val = Value.fromInterned(payload),
+            }, writer, level, mod, opt_sema),
         },
-        .enum_literal => |enum_literal| return writer.print(".{}", .{
+        .enum_literal => |enum_literal| try writer.print(".{}", .{
             enum_literal.fmt(ip),
         }),
         .enum_tag => |enum_tag| {
-            if (level == 0) {
-                return writer.writeAll("(enum)");
-            }
-            const enum_type = ip.loadEnumType(ty.toIntern());
+            const enum_type = ip.loadEnumType(val.typeOf(mod).toIntern());
             if (enum_type.tagValueIndex(ip, val.toIntern())) |tag_index| {
                 try writer.print(".{i}", .{enum_type.names.get(ip)[tag_index].fmt(ip)});
                 return;
             }
+            if (level == 0) {
+                try writer.writeAll("@enumFromInt(...)");
+            }
             try writer.writeAll("@enumFromInt(");
             try print(.{
                 .ty = Type.fromInterned(ip.typeOf(enum_tag.int)),
                 .val = Value.fromInterned(enum_tag.int),
-            }, writer, level - 1, mod);
+            }, writer, level - 1, mod, opt_sema);
             try writer.writeAll(")");
-            return;
         },
-        .empty_enum_value => return writer.writeAll("(empty enum value)"),
+        .empty_enum_value => try writer.writeAll("(empty enum value)"),
         .float => |float| switch (float.storage) {
-            inline else => |x| return writer.print("{d}", .{@as(f64, @floatCast(x))}),
+            inline else => |x| try writer.print("{d}", .{@as(f64, @floatCast(x))}),
         },
         .slice => |slice| {
-            const ptr_ty = switch (ip.indexToKey(slice.ptr)) {
-                .ptr => |ptr| ty: {
-                    if (ptr.addr == .int) return print(.{
-                        .ty = Type.fromInterned(ptr.ty),
-                        .val = Value.fromInterned(slice.ptr),
-                    }, writer, level - 1, mod);
-                    break :ty ip.indexToKey(ptr.ty).ptr_type;
-                },
-                .undef => |ptr_ty| ip.indexToKey(ptr_ty).ptr_type,
-                else => unreachable,
+            const print_contents = switch (ip.getBackingAddrTag(slice.ptr).?) {
+                .field, .elem, .eu_payload, .opt_payload => unreachable,
+                .anon_decl, .comptime_alloc, .comptime_field => true,
+                .decl, .int => false,
             };
-            if (level == 0) {
-                return writer.writeAll(".{ ... }");
-            }
-            const elem_ty = Type.fromInterned(ptr_ty.child);
-            const len = Value.fromInterned(slice.len).toUnsignedInt(mod);
-            if (elem_ty.eql(Type.u8, mod)) str: {
-                const max_len = @min(len, max_string_len);
-                var buf: [max_string_len]u8 = undefined;
-                for (buf[0..max_len], 0..) |*c, i| {
-                    const maybe_elem = try val.maybeElemValue(mod, i);
-                    const elem = maybe_elem orelse return writer.writeAll(".{ (reinterpreted data) }");
-                    if (elem.isUndef(mod)) break :str;
-                    c.* = @as(u8, @intCast(elem.toUnsignedInt(mod)));
-                }
-                const truncated = if (len > max_string_len) " (truncated)" else "";
-                return writer.print("\"{}{s}\"", .{ std.zig.fmtEscapes(buf[0..max_len]), truncated });
+            if (print_contents) {
+                // TODO: eventually we want to load the slice as an array with `opt_sema`, but that's
+                // currently not possible without e.g. triggering compile errors.
             }
-            try writer.writeAll(".{ ");
-            const max_len = @min(len, max_aggregate_items);
-            for (0..max_len) |i| {
-                if (i != 0) try writer.writeAll(", ");
-                const maybe_elem = try val.maybeElemValue(mod, i);
-                const elem = maybe_elem orelse return writer.writeAll("(reinterpreted data) }");
-                try print(.{
-                    .ty = elem_ty,
-                    .val = elem,
-                }, writer, level - 1, mod);
-            }
-            if (len > max_aggregate_items) {
-                try writer.writeAll(", ...");
-            }
-            return writer.writeAll(" }");
+            try printPtr(slice.ptr, writer, false, false, 0, level, mod, opt_sema);
+            try writer.writeAll("[0..");
+            try print(.{
+                .ty = Type.usize,
+                .val = Value.fromInterned(slice.len),
+            }, writer, level - 1, mod, opt_sema);
+            try writer.writeAll("]");
         },
-        .ptr => |ptr| {
-            switch (ptr.addr) {
-                .decl => |decl_index| {
-                    const decl = mod.declPtr(decl_index);
-                    if (level == 0) return writer.print("(decl '{}')", .{decl.name.fmt(ip)});
-                    return print(.{
-                        .ty = decl.typeOf(mod),
-                        .val = decl.val,
-                    }, writer, level - 1, mod);
-                },
-                .anon_decl => |anon_decl| {
-                    const decl_val = anon_decl.val;
-                    if (level == 0) return writer.print("(anon decl '{d}')", .{
-                        @intFromEnum(decl_val),
-                    });
-                    return print(.{
-                        .ty = Type.fromInterned(ip.typeOf(decl_val)),
-                        .val = Value.fromInterned(decl_val),
-                    }, writer, level - 1, mod);
-                },
-                .comptime_alloc => {
-                    // TODO: we need a Sema to print this!
-                    return writer.writeAll("(comptime alloc)");
-                },
-                .comptime_field => |field_val_ip| {
-                    return print(.{
-                        .ty = Type.fromInterned(ip.typeOf(field_val_ip)),
-                        .val = Value.fromInterned(field_val_ip),
-                    }, writer, level - 1, mod);
-                },
-                .int => |int_ip| {
-                    try writer.writeAll("@ptrFromInt(");
-                    try print(.{
-                        .ty = Type.usize,
-                        .val = Value.fromInterned(int_ip),
-                    }, writer, level - 1, mod);
-                    try writer.writeByte(')');
-                },
-                .eu_payload => |eu_ip| {
-                    try writer.writeAll("(payload of ");
-                    try print(.{
-                        .ty = Type.fromInterned(ip.typeOf(eu_ip)),
-                        .val = Value.fromInterned(eu_ip),
-                    }, writer, level - 1, mod);
-                    try writer.writeAll(")");
-                },
-                .opt_payload => |opt_ip| {
-                    try print(.{
-                        .ty = Type.fromInterned(ip.typeOf(opt_ip)),
-                        .val = Value.fromInterned(opt_ip),
-                    }, writer, level - 1, mod);
-                    try writer.writeAll(".?");
-                },
-                .elem => |elem| {
-                    if (level == 0) {
-                        try writer.writeAll("(...)");
-                    } else {
-                        try print(.{
-                            .ty = Type.fromInterned(ip.typeOf(elem.base)),
-                            .val = Value.fromInterned(elem.base),
-                        }, writer, level - 1, mod);
-                    }
-                    try writer.print("[{}]", .{elem.index});
-                },
-                .field => |field| {
-                    const ptr_container_ty = Type.fromInterned(ip.typeOf(field.base));
-                    if (level == 0) {
-                        try writer.writeAll("(...)");
-                    } else {
-                        try print(.{
-                            .ty = ptr_container_ty,
-                            .val = Value.fromInterned(field.base),
-                        }, writer, level - 1, mod);
-                    }
-
-                    const container_ty = ptr_container_ty.childType(mod);
-                    switch (container_ty.zigTypeTag(mod)) {
-                        .Struct => {
-                            if (container_ty.structFieldName(@intCast(field.index), mod).unwrap()) |field_name| {
-                                try writer.print(".{i}", .{field_name.fmt(ip)});
-                            } else {
-                                try writer.print("[{d}]", .{field.index});
-                            }
-                        },
-                        .Union => {
-                            const field_name = mod.typeToUnion(container_ty).?.loadTagType(ip).names.get(ip)[@intCast(field.index)];
-                            try writer.print(".{i}", .{field_name.fmt(ip)});
-                        },
-                        .Pointer => {
-                            std.debug.assert(container_ty.isSlice(mod));
-                            try writer.writeAll(switch (field.index) {
-                                Value.slice_ptr_index => ".ptr",
-                                Value.slice_len_index => ".len",
-                                else => unreachable,
-                            });
-                        },
-                        else => unreachable,
-                    }
-                },
+        .ptr => {
+            const print_contents = switch (ip.getBackingAddrTag(val.toIntern()).?) {
+                .field, .elem, .eu_payload, .opt_payload => unreachable,
+                .anon_decl, .comptime_alloc, .comptime_field => true,
+                .decl, .int => false,
+            };
+            if (print_contents) {
+                // TODO: eventually we want to load the pointer with `opt_sema`, but that's
+                // currently not possible without e.g. triggering compile errors.
             }
-            return;
+            try printPtr(val.toIntern(), writer, false, false, 0, level, mod, opt_sema);
         },
         .opt => |opt| switch (opt.val) {
-            .none => return writer.writeAll("null"),
-            else => |payload| {
-                val = Value.fromInterned(payload);
-                ty = ty.optionalChild(mod);
-            },
-        },
-        .aggregate => |aggregate| switch (aggregate.storage) {
-            .bytes => |bytes| {
-                // Strip the 0 sentinel off of strings before printing
-                const zero_sent = blk: {
-                    const sent = ty.sentinel(mod) orelse break :blk false;
-                    break :blk sent.eql(Value.zero_u8, Type.u8, mod);
-                };
-                const str = if (zero_sent) bytes[0 .. bytes.len - 1] else bytes;
-                return writer.print("\"{}\"", .{std.zig.fmtEscapes(str)});
-            },
-            .elems, .repeated_elem => return printAggregate(ty, val, writer, level, mod),
+            .none => try writer.writeAll("null"),
+            else => |payload| try print(.{
+                .ty = tv.ty.childType(mod),
+                .val = Value.fromInterned(payload),
+            }, writer, level, mod, opt_sema),
         },
+        .aggregate => |aggregate| try printAggregate(val, aggregate, writer, level, mod, opt_sema),
         .un => |un| {
-            try writer.writeAll(".{ ");
-            if (level > 0) {
-                if (un.tag != .none) {
-                    try print(.{
-                        .ty = ty.unionTagTypeHypothetical(mod),
-                        .val = Value.fromInterned(un.tag),
-                    }, writer, level - 1, mod);
-                    try writer.writeAll(" = ");
-                    const field_ty = ty.unionFieldType(Value.fromInterned(un.tag), mod).?;
-                    try print(.{
-                        .ty = field_ty,
-                        .val = Value.fromInterned(un.val),
-                    }, writer, level - 1, mod);
-                } else {
-                    try writer.writeAll("(unknown tag) = ");
-                    const backing_ty = try ty.unionBackingType(mod);
-                    try print(.{
-                        .ty = backing_ty,
-                        .val = Value.fromInterned(un.val),
-                    }, writer, level - 1, mod);
-                }
-            } else try writer.writeAll("...");
-            return writer.writeAll(" }");
+            if (level == 0) {
+                try writer.writeAll(".{ ... }");
+                return;
+            }
+            if (un.tag == .none) {
+                const backing_ty = try tv.ty.unionBackingType(mod);
+                try writer.print("@bitCast(@as({}, ", .{backing_ty.fmt(mod)});
+                try print(.{
+                    .ty = backing_ty,
+                    .val = Value.fromInterned(un.val),
+                }, writer, level - 1, mod, opt_sema);
+                try writer.writeAll("))");
+            } else {
+                try writer.writeAll(".{ ");
+                try print(.{
+                    .ty = tv.ty.unionTagTypeHypothetical(mod),
+                    .val = Value.fromInterned(un.tag),
+                }, writer, level - 1, mod, opt_sema);
+                try writer.writeAll(" = ");
+                const field_ty = tv.ty.unionFieldType(Value.fromInterned(un.tag), mod).?;
+                try print(.{
+                    .ty = field_ty,
+                    .val = Value.fromInterned(un.val),
+                }, writer, level - 1, mod, opt_sema);
+                try writer.writeAll(" }");
+            }
         },
         .memoized_call => unreachable,
-    };
+    }
 }
 
 fn printAggregate(
-    ty: Type,
     val: Value,
+    aggregate: InternPool.Key.Aggregate,
     writer: anytype,
     level: u8,
-    mod: *Module,
-) (@TypeOf(writer).Error || Allocator.Error)!void {
+    zcu: *Zcu,
+    opt_sema: ?*Sema,
+) (@TypeOf(writer).Error || Module.CompileError)!void {
     if (level == 0) {
         return writer.writeAll(".{ ... }");
     }
-    const ip = &mod.intern_pool;
-    if (ty.zigTypeTag(mod) == .Struct) {
-        try writer.writeAll(".{");
-        const max_len = @min(ty.structFieldCount(mod), max_aggregate_items);
-
-        for (0..max_len) |i| {
-            if (i != 0) try writer.writeAll(", ");
+    const ip = &zcu.intern_pool;
+    const ty = Type.fromInterned(aggregate.ty);
+    switch (ty.zigTypeTag(zcu)) {
+        .Struct => if (!ty.isTuple(zcu)) {
+            if (ty.structFieldCount(zcu) == 0) {
+                return writer.writeAll(".{}");
+            }
+            try writer.writeAll(".{ ");
+            const max_len = @min(ty.structFieldCount(zcu), max_aggregate_items);
+            for (0..max_len) |i| {
+                if (i != 0) try writer.writeAll(", ");
+                const field_name = ty.structFieldName(@intCast(i), zcu).unwrap().?;
+                try writer.print(".{i} = ", .{field_name.fmt(ip)});
+                try print(.{
+                    .ty = ty.structFieldType(i, zcu),
+                    .val = try val.fieldValue(zcu, i),
+                }, writer, level - 1, zcu, opt_sema);
+            }
+            try writer.writeAll(" }");
+            return;
+        },
+        .Array => if (aggregate.storage == .bytes) {
+            return writer.print("\"{}\".*", .{std.zig.fmtEscapes(aggregate.storage.bytes)});
+        } else if (ty.arrayLen(zcu) == 0) {
+            return writer.writeAll(".{}");
+        },
+        .Vector => if (ty.arrayLen(zcu) == 0) {
+            return writer.writeAll(".{}");
+        },
+        else => unreachable,
+    }
 
-            const field_name = ty.structFieldName(@intCast(i), mod);
+    const elem_ty = ty.childType(zcu);
+    const len = ty.arrayLen(zcu);
 
-            if (field_name.unwrap()) |name| try writer.print(".{} = ", .{name.fmt(ip)});
-            try print(.{
-                .ty = ty.structFieldType(i, mod),
-                .val = try val.fieldValue(mod, i),
-            }, writer, level - 1, mod);
-        }
-        if (ty.structFieldCount(mod) > max_aggregate_items) {
-            try writer.writeAll(", ...");
-        }
-        return writer.writeAll("}");
-    } else {
-        const elem_ty = ty.elemType2(mod);
-        const len = ty.arrayLen(mod);
+    try writer.writeAll(".{ ");
 
-        if (elem_ty.eql(Type.u8, mod)) str: {
-            const max_len: usize = @min(len, max_string_len);
-            var buf: [max_string_len]u8 = undefined;
+    const max_len = @min(len, max_aggregate_items);
+    for (0..max_len) |i| {
+        if (i != 0) try writer.writeAll(", ");
+        try print(.{
+            .ty = elem_ty,
+            .val = try val.fieldValue(zcu, i),
+        }, writer, level - 1, zcu, opt_sema);
+    }
+    if (len > max_aggregate_items) {
+        try writer.writeAll(", ...");
+    }
+    return writer.writeAll(" }");
+}
 
-            var i: u32 = 0;
-            while (i < max_len) : (i += 1) {
-                const elem = try val.fieldValue(mod, i);
-                if (elem.isUndef(mod)) break :str;
-                buf[i] = std.math.cast(u8, elem.toUnsignedInt(mod)) orelse break :str;
+fn printPtr(
+    ptr_val: InternPool.Index,
+    writer: anytype,
+    force_type: bool,
+    force_addrof: bool,
+    leading_parens: u32,
+    level: u8,
+    zcu: *Zcu,
+    opt_sema: ?*Sema,
+) (@TypeOf(writer).Error || Module.CompileError)!void {
+    const ip = &zcu.intern_pool;
+    const ptr = switch (ip.indexToKey(ptr_val)) {
+        .undef => |ptr_ty| {
+            if (force_addrof) try writer.writeAll("&");
+            try writer.writeByteNTimes('(', leading_parens);
+            try writer.print("@as({}, undefined)", .{Type.fromInterned(ptr_ty).fmt(zcu)});
+            return;
+        },
+        .ptr => |ptr| ptr,
+        else => unreachable,
+    };
+    switch (ptr.addr) {
+        .int => |int| {
+            if (force_addrof) try writer.writeAll("&");
+            try writer.writeByteNTimes('(', leading_parens);
+            if (force_type) {
+                try writer.print("@as({}, @ptrFromInt(", .{Type.fromInterned(ptr.ty).fmt(zcu)});
+                try print(.{
+                    .ty = Type.usize,
+                    .val = Value.fromInterned(int),
+                }, writer, level - 1, zcu, opt_sema);
+                try writer.writeAll("))");
+            } else {
+                try writer.writeAll("@ptrFromInt(");
+                try print(.{
+                    .ty = Type.usize,
+                    .val = Value.fromInterned(int),
+                }, writer, level - 1, zcu, opt_sema);
+                try writer.writeAll(")");
             }
-
-            const truncated = if (len > max_string_len) " (truncated)" else "";
-            return writer.print("\"{}{s}\"", .{ std.zig.fmtEscapes(buf[0..max_len]), truncated });
-        }
-
-        try writer.writeAll(".{ ");
-
-        const max_len = @min(len, max_aggregate_items);
-        var i: u32 = 0;
-        while (i < max_len) : (i += 1) {
-            if (i != 0) try writer.writeAll(", ");
+        },
+        .decl => |index| {
+            try writer.writeAll("&");
+            try zcu.declPtr(index).renderFullyQualifiedName(zcu, writer);
+        },
+        .comptime_alloc => try writer.writeAll("&(comptime alloc)"),
+        .anon_decl => |anon| {
+            const ty = Type.fromInterned(ip.typeOf(anon.val));
+            try writer.print("&@as({}, ", .{ty.fmt(zcu)});
             try print(.{
-                .ty = elem_ty,
-                .val = try val.fieldValue(mod, i),
-            }, writer, level - 1, mod);
-        }
-        if (len > max_aggregate_items) {
-            try writer.writeAll(", ...");
-        }
-        return writer.writeAll(" }");
+                .ty = ty,
+                .val = Value.fromInterned(anon.val),
+            }, writer, level - 1, zcu, opt_sema);
+            try writer.writeAll(")");
+        },
+        .comptime_field => |val| {
+            const ty = Type.fromInterned(ip.typeOf(val));
+            try writer.print("&@as({}, ", .{ty.fmt(zcu)});
+            try print(.{
+                .ty = ty,
+                .val = Value.fromInterned(val),
+            }, writer, level - 1, zcu, opt_sema);
+            try writer.writeAll(")");
+        },
+        .eu_payload => |base| {
+            try printPtr(base, writer, true, true, leading_parens, level, zcu, opt_sema);
+            try writer.writeAll(".?");
+        },
+        .opt_payload => |base| {
+            try writer.writeAll("(");
+            try printPtr(base, writer, true, true, leading_parens + 1, level, zcu, opt_sema);
+            try writer.writeAll(" catch unreachable");
+        },
+        .elem => |elem| {
+            try printPtr(elem.base, writer, true, true, leading_parens, level, zcu, opt_sema);
+            try writer.print("[{d}]", .{elem.index});
+        },
+        .field => |field| {
+            try printPtr(field.base, writer, true, true, leading_parens, level, zcu, opt_sema);
+            const base_ty = Type.fromInterned(ip.typeOf(field.base)).childType(zcu);
+            switch (base_ty.zigTypeTag(zcu)) {
+                .Struct => if (base_ty.isTuple(zcu)) {
+                    try writer.print("[{d}]", .{field.index});
+                } else {
+                    const field_name = base_ty.structFieldName(@intCast(field.index), zcu).unwrap().?;
+                    try writer.print(".{i}", .{field_name.fmt(ip)});
+                },
+                .Union => {
+                    const tag_ty = base_ty.unionTagTypeHypothetical(zcu);
+                    const field_name = tag_ty.enumFieldName(@intCast(field.index), zcu);
+                    try writer.print(".{i}", .{field_name.fmt(ip)});
+                },
+                .Pointer => switch (field.index) {
+                    Value.slice_ptr_index => try writer.writeAll(".ptr"),
+                    Value.slice_len_index => try writer.writeAll(".len"),
+                    else => unreachable,
+                },
+                else => unreachable,
+            }
+        },
     }
 }
src/Value.zig
@@ -305,16 +305,16 @@ pub fn toBool(val: Value) bool {
     };
 }
 
-fn isDeclRef(val: Value, mod: *Module) bool {
+fn ptrHasIntAddr(val: Value, mod: *Module) bool {
     var check = val;
     while (true) switch (mod.intern_pool.indexToKey(check.toIntern())) {
         .ptr => |ptr| switch (ptr.addr) {
-            .decl, .comptime_alloc, .comptime_field, .anon_decl => return true,
+            .decl, .comptime_alloc, .comptime_field, .anon_decl => return false,
+            .int => return true,
             .eu_payload, .opt_payload => |base| check = Value.fromInterned(base),
             .elem, .field => |base_index| check = Value.fromInterned(base_index.base),
-            .int => return false,
         },
-        else => return false,
+        else => unreachable,
     };
 }
 
@@ -439,7 +439,7 @@ pub fn writeToMemory(val: Value, ty: Type, mod: *Module, buffer: []u8) error{
         },
         .Pointer => {
             if (ty.isSlice(mod)) return error.IllDefinedMemoryLayout;
-            if (val.isDeclRef(mod)) return error.ReinterpretDeclRef;
+            if (!val.ptrHasIntAddr(mod)) return error.ReinterpretDeclRef;
             return val.writeToMemory(Type.usize, mod, buffer);
         },
         .Optional => {
@@ -566,7 +566,7 @@ pub fn writeToPackedMemory(
         },
         .Pointer => {
             assert(!ty.isSlice(mod)); // No well defined layout.
-            if (val.isDeclRef(mod)) return error.ReinterpretDeclRef;
+            if (!val.ptrHasIntAddr(mod)) return error.ReinterpretDeclRef;
             return val.writeToPackedMemory(Type.usize, mod, buffer, bit_offset);
         },
         .Optional => {
@@ -1261,62 +1261,23 @@ pub fn slicePtr(val: Value, mod: *Module) Value {
     return Value.fromInterned(mod.intern_pool.slicePtr(val.toIntern()));
 }
 
-pub fn sliceLen(val: Value, mod: *Module) u64 {
-    const ip = &mod.intern_pool;
-    return switch (ip.indexToKey(val.toIntern())) {
-        .ptr => |ptr| switch (ip.indexToKey(switch (ptr.addr) {
-            .decl => |decl| mod.declPtr(decl).typeOf(mod).toIntern(),
-            .comptime_alloc => @panic("TODO"),
-            .anon_decl => |anon_decl| ip.typeOf(anon_decl.val),
-            .comptime_field => |comptime_field| ip.typeOf(comptime_field),
-            else => unreachable,
-        })) {
-            .array_type => |array_type| array_type.len,
-            else => 1,
-        },
-        .slice => |slice| Value.fromInterned(slice.len).toUnsignedInt(mod),
-        else => unreachable,
-    };
-}
-
-/// Asserts the value is a single-item pointer to an array, or an array,
-/// or an unknown-length pointer, and returns the element value at the index.
-pub fn elemValue(val: Value, mod: *Module, index: usize) Allocator.Error!Value {
-    return (try val.maybeElemValue(mod, index)).?;
-}
-
-/// Like `elemValue`, but returns `null` instead of asserting on failure.
-pub fn maybeElemValue(val: Value, mod: *Module, index: usize) Allocator.Error!?Value {
-    return val.maybeElemValueFull(null, mod, index);
+/// Gets the `len` field of a slice value as a `u64`.
+/// Resolves the length using the provided `Sema` if necessary.
+pub fn sliceLen(val: Value, sema: *Sema) !u64 {
+    return Value.fromInterned(sema.mod.intern_pool.sliceLen(val.toIntern())).toUnsignedIntAdvanced(sema);
 }
 
-pub fn maybeElemValueFull(val: Value, sema: ?*Sema, mod: *Module, index: usize) Allocator.Error!?Value {
-    return switch (mod.intern_pool.indexToKey(val.toIntern())) {
-        .undef => |ty| Value.fromInterned((try mod.intern(.{
-            .undef = Type.fromInterned(ty).elemType2(mod).toIntern(),
-        }))),
-        .slice => |slice| return Value.fromInterned(slice.ptr).maybeElemValueFull(sema, mod, index),
-        .ptr => |ptr| switch (ptr.addr) {
-            .decl => |decl| mod.declPtr(decl).val.maybeElemValueFull(sema, mod, index),
-            .anon_decl => |anon_decl| Value.fromInterned(anon_decl.val).maybeElemValueFull(sema, mod, index),
-            .comptime_alloc => |idx| if (sema) |s| Value.fromInterned(
-                try s.getComptimeAlloc(idx).val.intern(mod, s.arena),
-            ).maybeElemValueFull(sema, mod, index) else null,
-            .int, .eu_payload => null,
-            .opt_payload => |base| Value.fromInterned(base).maybeElemValueFull(sema, mod, index),
-            .comptime_field => |field_val| Value.fromInterned(field_val).maybeElemValueFull(sema, mod, index),
-            .elem => |elem| Value.fromInterned(elem.base).maybeElemValueFull(sema, mod, index + @as(usize, @intCast(elem.index))),
-            .field => |field| if (Value.fromInterned(field.base).pointerDecl(mod)) |decl_index| {
-                const base_decl = mod.declPtr(decl_index);
-                const field_val = try base_decl.val.fieldValue(mod, @as(usize, @intCast(field.index)));
-                return field_val.maybeElemValueFull(sema, mod, index);
-            } else null,
-        },
-        .opt => |opt| Value.fromInterned(opt.val).maybeElemValueFull(sema, mod, index),
+/// Asserts the value is an aggregate, and returns the element value at the given index.
+pub fn elemValue(val: Value, zcu: *Zcu, index: usize) Allocator.Error!Value {
+    const ip = &zcu.intern_pool;
+    switch (zcu.intern_pool.indexToKey(val.toIntern())) {
+        .undef => |ty| {
+            return Value.fromInterned(try zcu.intern(.{ .undef = Type.fromInterned(ty).childType(zcu).toIntern() }));
+        },
         .aggregate => |aggregate| {
-            const len = mod.intern_pool.aggregateTypeLen(aggregate.ty);
+            const len = ip.aggregateTypeLen(aggregate.ty);
             if (index < len) return Value.fromInterned(switch (aggregate.storage) {
-                .bytes => |bytes| try mod.intern(.{ .int = .{
+                .bytes => |bytes| try zcu.intern(.{ .int = .{
                     .ty = .u8_type,
                     .storage = .{ .u64 = bytes[index] },
                 } }),
@@ -1324,10 +1285,10 @@ pub fn maybeElemValueFull(val: Value, sema: ?*Sema, mod: *Module, index: usize)
                 .repeated_elem => |elem| elem,
             });
             assert(index == len);
-            return Value.fromInterned(mod.intern_pool.indexToKey(aggregate.ty).array_type.sentinel);
+            return Type.fromInterned(aggregate.ty).sentinel(zcu).?;
         },
-        else => null,
-    };
+        else => unreachable,
+    }
 }
 
 pub fn isLazyAlign(val: Value, mod: *Module) bool {
@@ -1359,39 +1320,26 @@ pub fn sliceArray(
 ) error{OutOfMemory}!Value {
     // TODO: write something like getCoercedInts to avoid needing to dupe
     const mod = sema.mod;
-    return switch (mod.intern_pool.indexToKey(val.toIntern())) {
-        .ptr => |ptr| switch (ptr.addr) {
-            .decl => |decl| try mod.declPtr(decl).val.sliceArray(sema, start, end),
-            .comptime_alloc => |idx| try Value.fromInterned(
-                try sema.getComptimeAlloc(idx).val.intern(mod, sema.arena),
-            ).sliceArray(sema, start, end),
-            .comptime_field => |comptime_field| Value.fromInterned(comptime_field)
-                .sliceArray(sema, start, end),
-            .elem => |elem| Value.fromInterned(elem.base)
-                .sliceArray(sema, start + @as(usize, @intCast(elem.index)), end + @as(usize, @intCast(elem.index))),
+    const aggregate = mod.intern_pool.indexToKey(val.toIntern()).aggregate;
+    return Value.fromInterned(try mod.intern(.{ .aggregate = .{
+        .ty = switch (mod.intern_pool.indexToKey(mod.intern_pool.typeOf(val.toIntern()))) {
+            .array_type => |array_type| try mod.arrayType(.{
+                .len = @as(u32, @intCast(end - start)),
+                .child = array_type.child,
+                .sentinel = if (end == array_type.len) array_type.sentinel else .none,
+            }),
+            .vector_type => |vector_type| try mod.vectorType(.{
+                .len = @as(u32, @intCast(end - start)),
+                .child = vector_type.child,
+            }),
             else => unreachable,
+        }.toIntern(),
+        .storage = switch (aggregate.storage) {
+            .bytes => .{ .bytes = try sema.arena.dupe(u8, mod.intern_pool.indexToKey(val.toIntern()).aggregate.storage.bytes[start..end]) },
+            .elems => .{ .elems = try sema.arena.dupe(InternPool.Index, mod.intern_pool.indexToKey(val.toIntern()).aggregate.storage.elems[start..end]) },
+            .repeated_elem => |elem| .{ .repeated_elem = elem },
         },
-        .aggregate => |aggregate| Value.fromInterned((try mod.intern(.{ .aggregate = .{
-            .ty = switch (mod.intern_pool.indexToKey(mod.intern_pool.typeOf(val.toIntern()))) {
-                .array_type => |array_type| try mod.arrayType(.{
-                    .len = @as(u32, @intCast(end - start)),
-                    .child = array_type.child,
-                    .sentinel = if (end == array_type.len) array_type.sentinel else .none,
-                }),
-                .vector_type => |vector_type| try mod.vectorType(.{
-                    .len = @as(u32, @intCast(end - start)),
-                    .child = vector_type.child,
-                }),
-                else => unreachable,
-            }.toIntern(),
-            .storage = switch (aggregate.storage) {
-                .bytes => .{ .bytes = try sema.arena.dupe(u8, mod.intern_pool.indexToKey(val.toIntern()).aggregate.storage.bytes[start..end]) },
-                .elems => .{ .elems = try sema.arena.dupe(InternPool.Index, mod.intern_pool.indexToKey(val.toIntern()).aggregate.storage.elems[start..end]) },
-                .repeated_elem => |elem| .{ .repeated_elem = elem },
-            },
-        } }))),
-        else => unreachable,
-    };
+    } }));
 }
 
 pub fn fieldValue(val: Value, mod: *Module, index: usize) !Value {
@@ -3586,6 +3534,10 @@ pub fn isGenericPoison(val: Value) bool {
     return val.toIntern() == .generic_poison;
 }
 
+pub fn typeOf(val: Value, zcu: *const Zcu) Type {
+    return Type.fromInterned(zcu.intern_pool.typeOf(val.toIntern()));
+}
+
 /// For an integer (comptime or fixed-width) `val`, returns the comptime-known bounds of the value.
 /// If `val` is not undef, the bounds are both `val`.
 /// If `val` is undef and has a fixed-width type, the bounds are the bounds of the type.
test/behavior/basic.zig
@@ -693,31 +693,6 @@ test "string concatenation" {
     try expect(b[len] == 0);
 }
 
-fn manyptrConcat(comptime s: [*:0]const u8) [*:0]const u8 {
-    return "very " ++ s;
-}
-
-test "comptime manyptr concatenation" {
-    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
-
-    const s = "epic";
-    const actual = manyptrConcat(s);
-    const expected = "very epic";
-
-    const len = mem.len(actual);
-    const len_with_null = len + 1;
-    {
-        var i: u32 = 0;
-        while (i < len_with_null) : (i += 1) {
-            try expect(actual[i] == expected[i]);
-        }
-    }
-    try expect(actual[len] == 0);
-    try expect(expected[len] == 0);
-}
-
 test "result location is optional inside error union" {
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO