stage1: Allow variable capture for multi-prong switch arms

Handle the multi-prong case as we do with range cases.

Closes #7188

Author: LemonBoy

src/stage1/ir.cpp

@@ -24207,6 +24207,8 @@ static IrInstGen *ir_analyze_instruction_switch_var(IrAnalyze *ira, IrInstSrcSwi
             ref_type->data.pointer.allow_zero);
         return ir_analyze_ptr_cast(ira, &instruction->base.base, target_value_ptr,
                 &instruction->target_value_ptr->base, new_target_value_ptr_type, &instruction->base.base, false, false);
+    } else if (instruction->prongs_len > 1) {
+        return target_value_ptr;
     } else {
         ir_add_error(ira, &instruction->base.base,
             buf_sprintf("switch on type '%s' provides no expression parameter", buf_ptr(&target_type->name)));

test/stage1/behavior/switch.zig

@@ -436,6 +436,26 @@ test "switch with disjoint range" {
     }
 }
 
+test "switch variable for range and multiple prongs" {
+    const S = struct {
+        fn doTheTest() void {
+            var u: u8 = 16;
+            doTheSwitch(u);
+            comptime doTheSwitch(u);
+            var v: u8 = 42;
+            doTheSwitch(v);
+            comptime doTheSwitch(v);
+        }
+        fn doTheSwitch(q: u8) void {
+            switch (q) {
+                0...40 => |x| expect(x == 16),
+                41, 42, 43 => |x| expect(x == 42),
+                else => expect(false),
+            }
+        }
+    };
+}
+
 var state: u32 = 0;
 fn poll() void {
     switch (state) {