address rvalue aggregates for field access

compiler_tests.odin

@@ -1089,6 +1089,53 @@ main :: func() i32 {
 	testing.expect(t, strings.contains(llvm_text, "getelementptr [4 x i32], ptr"))
 }
 
+@(test)
+field_and_index_access_on_an_rvalue_aggregate_materializes_it :: proc(t: ^testing.T) {
+	// A by-value struct return is a temporary with no address. Reading a field,
+	// slicing an array field, and taking its address must spill it into a
+	// temporary and address that, rather than addressing the aggregate value.
+	text := `Box :: struct {
+	score i32
+	data [4]i32
+}
+make_box :: func() Box {
+	return Box { score = 7, data = [1, 2, 3, 4] }
+}
+sink :: func(s []i32) i32 {
+	return s[0]
+}
+main :: func() i32 {
+	s :: make_box().score
+	v :: sink(make_box().data[0..])
+	p :: &make_box().data
+	return s + v + p^[1]
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+	ir_module := lower.lower(&hir_module)
+	defer ir.destroy_module(&ir_module)
+	llvm_text := llvm.emit(&ir_module, &diagnostics, &symbols)
+	defer delete(llvm_text)
+
+	testing.expect_value(t, len(diagnostics.items), 0)
+	// The rvalue Box is spilled into a stack temporary (structs render as
+	// %bro.type.N), then stored, then its fields are addressed off a `ptr`.
+	// A regression addresses the aggregate value directly, which llc rejects.
+	testing.expect(t, strings.contains(llvm_text, "alloca %bro.type."))
+	testing.expect(t, strings.contains(llvm_text, "store %bro.type."))
+	testing.expect(t, strings.contains(llvm_text, "getelementptr [4 x i32], ptr"))
+}
+
 @(test)
 c_variadic_calls_promote_extras_and_emit_variadic_llvm :: proc(t: ^testing.T) {
 text := `variadic :: c_func(tag c_int, ...) c_int