multi-line string literals

TODO.md

@@ -253,25 +253,29 @@
   - parser-only change (`parse_branch_body` in `compiler/parser/parser.odin`): a brace-less
     body is just a 1-element statement slice, so the checker and codegen are unchanged
 
-17. add slice-by-range
-  - allow the use of a range in slice expressions:
-    ```
-    excl_range range :: 0..10
-    some_arr[excl_range] # slice by named exclusive range
-  
-    incl_range range :: 0..=10
-    some_arr[incl_range] # slice by named inclusive range
-    ```
+17. multi-line strings (implemented; see below)
+  - a multi-line string is an ordinary string literal under the hood: it lowers to the
+    same `.String` expr / `@[N;0]u8` type, so the checker, lowering, and codegen are
+    unchanged. only the lexer and parser change.
+  - the lexer (`compiler/lexer/lexer.odin`, `` case '`' ``) collapses consecutive
+    backtick-marked lines into one `Multiline_String` token; the trailing newline after
+    the last line stays a `.Newline` so it terminates the statement normally
+  - the parser (`decode_multiline_string` in `compiler/parser/parser.odin`) strips each
+    line's leading indentation and `` ` ``, takes the rest of the line raw (no escapes),
+    and joins lines with an implicit `\n` (no leading/trailing newline); an empty
+    `` ` `` yields a blank line
+  - the value may sit on the line after `=`/`::` (the existing post-operator
+    `skip_newlines` already allows this)
+  - `++` concatenation (the spec's "mixing" examples) is a separate, unimplemented
+    operator and is out of scope here
 
 18. add `defer` statement (inspired by zig)
 
-19. multi-line strings (see below)
+19. unions and tagged unions
 
-20. unions and tagged unions
+20. match statements with tagged unions payload unwrapping
 
-21. match statements with tagged unions payload unwrapping
-
-22. dynamic heap allocation
+21. dynamic heap allocation
   - see below for direction
   - notes below are too big in scope for a first pass and the language is not mature enough to support it yet
   - this first pass should focus on just basic heap allocation, so we have something to work with

compiler/lexer/lexer.odin

@@ -277,6 +277,34 @@ lex :: proc(
 				)
 				append_token(&stream, source_file, .Invalid, start, cursor, diagnostic=id)
 			}
+		case '`':
+			// Multi-line string: each line is marked with a leading '`'; raw
+			// content (no escapes) runs to end of line. Consecutive backtick
+			// lines collapse into one token; the trailing '\n' is left to
+			// become the statement-terminating Newline.
+			start := cursor
+			content_end := cursor
+			for {
+				cursor += 1 // skip backtick
+				for cursor < len(bytes) && bytes[cursor] != '\n' {
+					cursor += 1
+				}
+				content_end = cursor
+				look := cursor
+				if look < len(bytes) && bytes[look] == '\n' {
+					look += 1
+				}
+				for look < len(bytes) && (bytes[look] == ' ' || bytes[look] == '\t') {
+					look += 1
+				}
+				if look < len(bytes) && bytes[look] == '`' {
+					cursor = look
+					continue
+				}
+				break
+			}
+			cursor = content_end
+			append_token(&stream, source_file, .Multiline_String, start, content_end)
 		case ';':
 			append_token(&stream, source_file, .Semicolon, cursor, cursor+1)
 			cursor += 1

compiler/parser/parser.odin

@@ -560,9 +560,9 @@ parse_primary :: proc(parser: ^Parser, nesting: int) -> ast.Expr_Id {
 			right=ast.INVALID_EXPR,
 			diagnostic=source.INVALID_DIAGNOSTIC,
 		})
-	case .String:
+	case .String, .Multiline_String:
 		advance(parser)
-		value := decode_import_path(parser, tok)
+		value := decode_import_path(parser, tok) if tok.kind == .String else decode_multiline_string(parser, tok)
 		id := u64(len(parser.module.strings))
 		append(&parser.module.strings, value)
 		return add_expr(parser, ast.Expr{
@@ -1690,6 +1690,33 @@ decode_import_path :: proc(parser: ^Parser, tok: token.Token) -> string {
 	return fmt.aprintf("%s", strings.to_string(builder), allocator=parser.module.allocator)
 }
 
+decode_multiline_string :: proc(parser: ^Parser, tok: token.Token) -> string {
+	text := token_text(parser, tok)
+	builder := strings.builder_make(parser.module.allocator)
+	defer strings.builder_destroy(&builder)
+	first := true
+	index := 0
+	for index < len(text) {
+		for index < len(text) && (text[index] == ' ' || text[index] == '\t') {
+			index += 1
+		}
+		if index >= len(text) || text[index] != '`' {
+			break
+		}
+		index += 1 // skip backtick
+		if !first {
+			strings.write_byte(&builder, '\n')
+		}
+		first = false
+		for index < len(text) && text[index] != '\n' {
+			strings.write_byte(&builder, text[index])
+			index += 1
+		}
+		index += 1 // skip newline (terminates this line)
+	}
+	return fmt.aprintf("%s", strings.to_string(builder), allocator=parser.module.allocator)
+}
+
 parse_import :: proc(parser: ^Parser, alias: token.Token, start: token.Token) {
 	skip_newlines(parser)
 	path_token := current(parser)

compiler/token/token.odin

@@ -11,6 +11,7 @@ Kind :: enum u8 {
 	Integer,
 	Float,
 	String,
+	Multiline_String,
 	Character,
 	Underscore,
 	Colon,

compiler_tests.odin

@@ -969,6 +969,47 @@ main :: func() void {
 	testing.expect(t, strings.contains(llvm_text, "declare i32 @take_c_sentinel(ptr)"))
 }
 
+@(test)
+multiline_strings_join_lines_and_strip_indentation :: proc(t: ^testing.T) {
+	// Source written double-quoted (not a raw `...` literal) because the
+	// backtick is the multi-line string marker. Covers basic join, the
+	// trailing-newline form, a blank line in the middle, and value-on-next-line.
+	text := "main :: func() void {\n" +
+		"\tbasic ::\n\t\t`a\n\t\t`b\n" +
+		"\ttrailing ::\n\t\t`hello\n\t\t`world\n\t\t`\n" +
+		"\tgapped ::\n\t\t`x\n\t\t`\n\t\t`y\n" +
+		"\t_ = basic\n\t_ = trailing\n\t_ = gapped\n}\n"
+	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)
+
+	testing.expect_value(t, len(diagnostics.items), 0)
+	testing.expect_value(t, len(ast_module.strings), 3)
+	testing.expect_value(t, ast_module.strings[0], "a\nb")
+	testing.expect_value(t, ast_module.strings[1], "hello\nworld\n")
+	testing.expect_value(t, ast_module.strings[2], "x\n\ny")
+
+	// A multi-line string is an ordinary string literal: @[N;0]u8.
+	string_type := types.INVALID
+	for expr in hir_module.exprs {
+		if expr.kind == .String {
+			string_type = expr.type
+			break
+		}
+	}
+	pointer, array, string_ok := types.array_pointer(string_type, &hir_module.types)
+	testing.expect(t, string_ok && !pointer.mutable && array.child == types.U8 &&
+		array.has_sentinel && array.sentinel == 0)
+}
+
 @(test)
 array_pointer_and_c_string_coercion_restrictions_are_diagnosed :: proc(t: ^testing.T) {
 	text := `take_c_string :: c_func(value *c_char) c_int