diff --git a/src/AstGen.zig b/src/AstGen.zig
index 0078057eef..b6a7450f3a 100644
--- a/src/AstGen.zig
+++ b/src/AstGen.zig
@@ -1349,7 +1349,10 @@ fn arrayInitExpr(
             }
         }
         const array_type_inst = try typeExpr(gz, scope, array_init.ast.type_expr);
-        _ = try gz.addUnNode(.validate_array_init_ty, array_type_inst, array_init.ast.type_expr);
+        _ = try gz.addPlNode(.validate_array_init_ty, node, Zir.Inst.ArrayInit{
+            .ty = array_type_inst,
+            .init_count = @intCast(u32, array_init.ast.elements.len),
+        });
         break :inst .{
             .array = array_type_inst,
             .elem = .none,
diff --git a/src/Module.zig b/src/Module.zig
index deff4620b9..4ac2775515 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -2728,6 +2728,21 @@ pub const SrcLoc = struct {
                 };
                 return nodeToSpan(tree, full.ast.value_expr);
             },
+            .node_offset_init_ty => |node_off| {
+                const tree = try src_loc.file_scope.getTree(gpa);
+                const node_tags = tree.nodes.items(.tag);
+                const parent_node = src_loc.declRelativeToNodeIndex(node_off);
+
+                var buf: [2]Ast.Node.Index = undefined;
+                const full: Ast.full.ArrayInit = switch (node_tags[parent_node]) {
+                    .array_init_one, .array_init_one_comma => tree.arrayInitOne(buf[0..1], parent_node),
+                    .array_init_dot_two, .array_init_dot_two_comma => tree.arrayInitDotTwo(&buf, parent_node),
+                    .array_init_dot, .array_init_dot_comma => tree.arrayInitDot(parent_node),
+                    .array_init, .array_init_comma => tree.arrayInit(parent_node),
+                    else => unreachable,
+                };
+                return nodeToSpan(tree, full.ast.type_expr);
+            },
         }
     }
 
@@ -3048,6 +3063,9 @@ pub const LazySrcLoc = union(enum) {
     /// The source location points to the default value of a field.
     /// The Decl is determined contextually.
     node_offset_field_default: i32,
+    /// The source location points to the type of an array or struct initializer.
+    /// The Decl is determined contextually.
+    node_offset_init_ty: i32,
 
     pub const nodeOffset = if (TracedOffset.want_tracing) nodeOffsetDebug else nodeOffsetRelease;
 
@@ -3126,6 +3144,7 @@ pub const LazySrcLoc = union(enum) {
             .node_offset_ptr_hostsize,
             .node_offset_container_tag,
             .node_offset_field_default,
+            .node_offset_init_ty,
             => .{
                 .file_scope = decl.getFileScope(),
                 .parent_decl_node = decl.src_node,
diff --git a/src/Sema.zig b/src/Sema.zig
index 5a70679b8d..74c8f0b48d 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -3493,19 +3493,43 @@ fn validateArrayInitTy(
     block: *Block,
     inst: Zir.Inst.Index,
 ) CompileError!void {
-    const inst_data = sema.code.instructions.items(.data)[inst].un_node;
+    const inst_data = sema.code.instructions.items(.data)[inst].pl_node;
     const src = inst_data.src();
-    const ty = try sema.resolveType(block, src, inst_data.operand);
+    const ty_src: LazySrcLoc = .{ .node_offset_init_ty = inst_data.src_node };
+    const extra = sema.code.extraData(Zir.Inst.ArrayInit, inst_data.payload_index).data;
+    const ty = try sema.resolveType(block, ty_src, extra.ty);
 
     switch (ty.zigTypeTag()) {
-        .Array, .Vector => return,
+        .Array => {
+            const array_len = ty.arrayLen();
+            if (extra.init_count != array_len) {
+                return sema.fail(block, src, "expected {d} array elements; found {d}", .{
+                    array_len, extra.init_count,
+                });
+            }
+            return;
+        },
+        .Vector => {
+            const array_len = ty.arrayLen();
+            if (extra.init_count != array_len) {
+                return sema.fail(block, src, "expected {d} vector elements; found {d}", .{
+                    array_len, extra.init_count,
+                });
+            }
+            return;
+        },
         .Struct => if (ty.isTuple()) {
-            // TODO validate element count
+            const array_len = ty.arrayLen();
+            if (extra.init_count > array_len) {
+                return sema.fail(block, src, "expected at most {d} tuple fields; found {d}", .{
+                    array_len, extra.init_count,
+                });
+            }
             return;
         },
         else => {},
     }
-    return sema.failWithArrayInitNotSupported(block, src, ty);
+    return sema.failWithArrayInitNotSupported(block, ty_src, ty);
 }
 
 fn validateStructInitTy(
@@ -3741,6 +3765,15 @@ fn validateStructInit(
 
             const default_val = struct_ty.structFieldDefaultValue(i);
             if (default_val.tag() == .unreachable_value) {
+                if (struct_ty.isTuple()) {
+                    const template = "missing tuple field with index {d}";
+                    if (root_msg) |msg| {
+                        try sema.errNote(block, init_src, msg, template, .{i});
+                    } else {
+                        root_msg = try sema.errMsg(block, init_src, template, .{i});
+                    }
+                    continue;
+                }
                 const field_name = struct_ty.structFieldName(i);
                 const template = "missing struct field: {s}";
                 const args = .{field_name};
@@ -3753,7 +3786,10 @@ fn validateStructInit(
             }
 
             const field_src = init_src; // TODO better source location
-            const default_field_ptr = try sema.structFieldPtrByIndex(block, init_src, struct_ptr, @intCast(u32, i), field_src, struct_ty, true);
+            const default_field_ptr = if (struct_ty.isTuple())
+                try sema.tupleFieldPtr(block, init_src, struct_ptr, field_src, @intCast(u32, i), true)
+            else
+                try sema.structFieldPtrByIndex(block, init_src, struct_ptr, @intCast(u32, i), field_src, struct_ty, true);
             const field_ty = sema.typeOf(default_field_ptr).childType();
             const init = try sema.addConstant(field_ty, default_val);
             try sema.storePtr2(block, init_src, default_field_ptr, init_src, init, field_src, .store);
@@ -3868,6 +3904,15 @@ fn validateStructInit(
 
         const default_val = struct_ty.structFieldDefaultValue(i);
         if (default_val.tag() == .unreachable_value) {
+            if (struct_ty.isTuple()) {
+                const template = "missing tuple field with index {d}";
+                if (root_msg) |msg| {
+                    try sema.errNote(block, init_src, msg, template, .{i});
+                } else {
+                    root_msg = try sema.errMsg(block, init_src, template, .{i});
+                }
+                continue;
+            }
             const field_name = struct_ty.structFieldName(i);
             const template = "missing struct field: {s}";
             const args = .{field_name};
@@ -3911,7 +3956,10 @@ fn validateStructInit(
         if (field_ptr != 0) continue;
 
         const field_src = init_src; // TODO better source location
-        const default_field_ptr = try sema.structFieldPtrByIndex(block, init_src, struct_ptr, @intCast(u32, i), field_src, struct_ty, true);
+        const default_field_ptr = if (struct_ty.isTuple())
+            try sema.tupleFieldPtr(block, init_src, struct_ptr, field_src, @intCast(u32, i), true)
+        else
+            try sema.structFieldPtrByIndex(block, init_src, struct_ptr, @intCast(u32, i), field_src, struct_ty, true);
         const field_ty = sema.typeOf(default_field_ptr).childType();
         const init = try sema.addConstant(field_ty, field_values[i]);
         try sema.storePtr2(block, init_src, default_field_ptr, init_src, init, field_src, .store);
@@ -3934,15 +3982,24 @@ fn zirValidateArrayInit(
     const array_ty = sema.typeOf(array_ptr).childType();
     const array_len = array_ty.arrayLen();
 
-    if (instrs.len != array_len) {
-        if (array_ty.zigTypeTag() == .Array) {
-            return sema.fail(block, init_src, "expected {d} array elements; found {d}", .{
-                array_len, instrs.len,
-            });
-        } else {
-            return sema.fail(block, init_src, "expected {d} vector elements; found {d}", .{
-                array_len, instrs.len,
-            });
+    if (instrs.len != array_len and array_ty.isTuple()) {
+        const struct_obj = array_ty.castTag(.tuple).?.data;
+        var root_msg: ?*Module.ErrorMsg = null;
+        for (struct_obj.values) |default_val, i| {
+            if (i < instrs.len) continue;
+
+            if (default_val.tag() == .unreachable_value) {
+                const template = "missing tuple field with index {d}";
+                if (root_msg) |msg| {
+                    try sema.errNote(block, init_src, msg, template, .{i});
+                } else {
+                    root_msg = try sema.errMsg(block, init_src, template, .{i});
+                }
+            }
+        }
+
+        if (root_msg) |msg| {
+            return sema.failWithOwnedErrorMsg(block, msg);
         }
     }
 
@@ -3995,10 +4052,17 @@ fn zirValidateArrayInit(
         }
         first_block_index = @minimum(first_block_index, block_index);
 
-        // Array has one possible value, so value is always comptime-known
-        if (opt_opv) |opv| {
-            element_vals[i] = opv;
-            continue;
+        if (array_ty.isTuple()) {
+            if (array_ty.structFieldValueComptime(i)) |opv| {
+                element_vals[i] = opv;
+                continue;
+            }
+        } else {
+            // Array has one possible value, so value is always comptime-known
+            if (opt_opv) |opv| {
+                element_vals[i] = opv;
+                continue;
+            }
         }
 
         // If the next instructon is a store with a comptime operand, this element
@@ -14710,6 +14774,22 @@ fn finishStructInit(
                 field_inits[i] = try sema.addConstant(struct_obj.types[i], default_val);
             }
         }
+    } else if (struct_ty.isTuple()) {
+        const struct_obj = struct_ty.castTag(.tuple).?.data;
+        for (struct_obj.values) |default_val, i| {
+            if (field_inits[i] != .none) continue;
+
+            if (default_val.tag() == .unreachable_value) {
+                const template = "missing tuple field with index {d}";
+                if (root_msg) |msg| {
+                    try sema.errNote(block, init_src, msg, template, .{i});
+                } else {
+                    root_msg = try sema.errMsg(block, init_src, template, .{i});
+                }
+            } else {
+                field_inits[i] = try sema.addConstant(struct_obj.types[i], default_val);
+            }
+        }
     } else {
         const struct_obj = struct_ty.castTag(.@"struct").?.data;
         for (struct_obj.fields.values()) |field, i| {
@@ -20255,7 +20335,7 @@ fn tupleFieldVal(
     return tupleFieldValByIndex(sema, block, src, tuple_byval, field_index, tuple_ty);
 }
 
-/// Don't forget to check for "len" before calling this.
+/// Asserts that `field_name` is not "len".
 fn tupleFieldIndex(
     sema: *Sema,
     block: *Block,
@@ -20263,8 +20343,12 @@ fn tupleFieldIndex(
     field_name: []const u8,
     field_name_src: LazySrcLoc,
 ) CompileError!u32 {
+    assert(!std.mem.eql(u8, field_name, "len"));
     if (std.fmt.parseUnsigned(u32, field_name, 10)) |field_index| {
         if (field_index < tuple_ty.structFieldCount()) return field_index;
+        return sema.fail(block, field_name_src, "index '{s}' out of bounds of tuple '{}'", .{
+            field_name, tuple_ty.fmt(sema.mod),
+        });
     } else |_| {}
 
     return sema.fail(block, field_name_src, "no field named '{s}' in tuple '{}'", .{
diff --git a/src/Zir.zig b/src/Zir.zig
index 4540032605..ccd677df0b 100644
--- a/src/Zir.zig
+++ b/src/Zir.zig
@@ -1709,7 +1709,7 @@ pub const Inst = struct {
                 .switch_capture_multi_ref = .switch_capture,
                 .array_base_ptr = .un_node,
                 .field_base_ptr = .un_node,
-                .validate_array_init_ty = .un_node,
+                .validate_array_init_ty = .pl_node,
                 .validate_struct_init_ty = .un_node,
                 .validate_struct_init = .pl_node,
                 .validate_struct_init_comptime = .pl_node,
@@ -3543,6 +3543,11 @@ pub const Inst = struct {
         line: u32,
         column: u32,
     };
+
+    pub const ArrayInit = struct {
+        ty: Ref,
+        init_count: u32,
+    };
 };
 
 pub const SpecialProng = enum { none, @"else", under };
diff --git a/src/print_zir.zig b/src/print_zir.zig
index 7723446f1c..6e33154bbd 100644
--- a/src/print_zir.zig
+++ b/src/print_zir.zig
@@ -229,7 +229,6 @@ const Writer = struct {
             .switch_cond_ref,
             .array_base_ptr,
             .field_base_ptr,
-            .validate_array_init_ty,
             .validate_struct_init_ty,
             .make_ptr_const,
             .validate_deref,
@@ -246,6 +245,7 @@ const Writer = struct {
             .bool_br_or,
             => try self.writeBoolBr(stream, inst),
 
+            .validate_array_init_ty => try self.writeValidateArrayInitTy(stream, inst),
             .array_type_sentinel => try self.writeArrayTypeSentinel(stream, inst),
             .param_type => try self.writeParamType(stream, inst),
             .ptr_type => try self.writePtrType(stream, inst),
@@ -577,6 +577,18 @@ const Writer = struct {
         try self.writeSrc(stream, inst_data.src());
     }
 
+    fn writeValidateArrayInitTy(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.ArrayInit, inst_data.payload_index).data;
+        try self.writeInstRef(stream, extra.ty);
+        try stream.print(", {d}) ", .{extra.init_count});
+        try self.writeSrc(stream, inst_data.src());
+    }
+
     fn writeArrayTypeSentinel(
         self: *Writer,
         stream: anytype,
diff --git a/test/cases/compile_errors/tuple_init_edge_cases.zig b/test/cases/compile_errors/tuple_init_edge_cases.zig
new file mode 100644
index 0000000000..32b52cdc1f
--- /dev/null
+++ b/test/cases/compile_errors/tuple_init_edge_cases.zig
@@ -0,0 +1,44 @@
+pub export fn entry1() void {
+    const T = @TypeOf(.{ 123, 3 });
+    var b = T{ .@"1" = 3 }; _ = b;
+    var c = T{ 123, 3 }; _ = c;
+    var d = T{}; _ = d;
+}
+pub export fn entry2() void {
+    var a: u32 = 2;
+    const T = @TypeOf(.{ 123, a });
+    var b = T{ .@"1" = 3 }; _ = b;
+    var c = T{ 123, 3 }; _ = c;
+    var d = T{}; _ = d;
+}
+pub export fn entry3() void {
+    var a: u32 = 2;
+    const T = @TypeOf(.{ 123, a });
+    var b = T{ .@"0" = 123 }; _ = b;
+}
+comptime {
+    var a: u32 = 2;
+    const T = @TypeOf(.{ 123, a });
+    var b = T{ .@"0" = 123 }; _ = b;
+    var c = T{ 123, 2 }; _ = c;
+    var d = T{}; _ = d;
+}
+pub export fn entry4() void {
+    var a: u32 = 2;
+    const T = @TypeOf(.{ 123, a });
+    var b = T{ 123, 4, 5 }; _ = b;
+}
+pub export fn entry5() void {
+    var a: u32 = 2;
+    const T = @TypeOf(.{ 123, a });
+    var b = T{ .@"0" = 123, .@"2" = 123, .@"1" = 123 }; _ = b;
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :12:14: error: missing tuple field with index 1
+// :17:14: error: missing tuple field with index 1
+// :29:14: error: expected at most 2 tuple fields; found 3
+// :34:30: error: index '2' out of bounds of tuple 'tuple{comptime comptime_int = 123, u32}'
diff --git a/test/cases/compile_errors/wrong_size_to_an_array_literal.zig b/test/cases/compile_errors/wrong_size_to_an_array_literal.zig
index bb8b3c215c..a38d8d4d85 100644
--- a/test/cases/compile_errors/wrong_size_to_an_array_literal.zig
+++ b/test/cases/compile_errors/wrong_size_to_an_array_literal.zig
@@ -7,4 +7,4 @@ comptime {
 // backend=stage2
 // target=native
 //
-// :2:31: error: index 2 outside array of length 2
+// :2:24: error: expected 2 array elements; found 3