hare

commit 559b994e6474c8b6a3f688ed8edcf587dac625f8
parent 3db5510b45e63de415152fd2c17e013581f0a37c
Author: Drew DeVault <sir@cmpwn.com>
Date:   Sat, 17 Apr 2021 08:36:05 -0400

hare::parse: implement if expressions

Diffstat:
M
hare/ast/expr.ha
 | 
8
++++----
M
hare/parse/+test/expr.ha
 | 
12
++++++++++++
M
hare/parse/expr.ha
 | 
19
++++++++++++++++++-
M
hare/unparse/expr.ha
 | 
15
++++++++++++++-

4 files changed, 48 insertions(+), 6 deletions(-)
diff --git a/hare/ast/expr.ha b/hare/ast/expr.ha
@@ -168,8 +168,8 @@ export type free_expr = *expr;
 // if (foo) bar else baz
 export type if_expr = struct {
 	cond: *expr,
-	true_branch: nullable *expr,
-	false_branch: nullable *expr,
+	tbranch: *expr,
+	fbranch: nullable *expr,
 };
 
 // :label. The ":" character is not included.
@@ -363,8 +363,8 @@ export fn expr_free(e: (expr | nullable *expr)) void = match (e) {
 		f: free_expr => expr_free(f: *expr),
 		i: if_expr => {
 			expr_free(i.cond);
-			expr_free(i.true_branch);
-			expr_free(i.false_branch);
+			expr_free(i.tbranch);
+			expr_free(i.fbranch);
 		},
 		l: len_expr => expr_free(l: *expr),
 		l: list_expr => {
diff --git a/hare/parse/+test/expr.ha b/hare/parse/+test/expr.ha
@@ -33,6 +33,18 @@
 ");
 };
 
+@test fn if_expr() void = {
+	roundtrip("export fn main() void = {
+	if (x == y) {
+		z;
+	};
+	if (y == x) z;
+	if (z == q) r else p;
+	if (a == b) c else if (d == e) f else g;
+};
+");
+};
+
 @test fn list() void = {
 	roundtrip("export fn main() void = {
 	2 + 2;
diff --git a/hare/parse/expr.ha b/hare/parse/expr.ha
@@ -15,7 +15,7 @@ export fn expression(lexer: *lex::lexer) (ast::expr | error) = {
 		ltok::LBRACE => expression_list(lexer),
 		ltok::MATCH => abort(), // TODO
 		ltok::SWITCH => abort(), // TODO
-		ltok::IF => abort(), // TODO
+		ltok::IF => if_expr(lexer),
 		ltok::FOR => abort(), // TODO
 		ltok::BREAK, ltok::CONTINUE, ltok::RETURN => control(lexer),
 		ltok::LET, ltok::CONST => abort(), // TODO
@@ -192,6 +192,23 @@ fn expression_list(lexer: *lex::lexer) (ast::expr | error) = {
 	return items;
 };
 
+fn if_expr(lexer: *lex::lexer) (ast::expr | error) = {
+	want(lexer, ltok::IF)?;
+	want(lexer, ltok::LPAREN)?;
+	const cond = alloc(expression(lexer)?);
+	want(lexer, ltok::RPAREN)?;
+	const tbranch = alloc(expression(lexer)?);
+	const fbranch: nullable *ast::expr = match (try(lexer, ltok::ELSE)?) {
+		void => null,
+		lex::token => alloc(expression(lexer)?),
+	};
+	return ast::if_expr {
+		cond = cond,
+		tbranch = tbranch,
+		fbranch = fbranch,
+	};
+};
+
 fn indexing(lexer: *lex::lexer, lvalue: ast::expr) (ast::expr | error) = {
 	let is_slice = false;
 	let start: nullable *ast::expr = null, end: nullable *ast::expr = null;
diff --git a/hare/unparse/expr.ha b/hare/unparse/expr.ha
@@ -108,7 +108,20 @@ export fn expr(
 		e: ast::delete_expr => abort(),
 		e: ast::for_expr => abort(),
 		e: ast::free_expr => abort(),
-		e: ast::if_expr => abort(),
+		e: ast::if_expr => {
+			let z = fmt::fprint(out, "if (")?;
+			z += expr(out, indent, *e.cond)?;
+			z += fmt::fprint(out, ") ")?;
+			z += expr(out, indent, *e.tbranch)?;
+			match (e.fbranch) {
+				null => void,
+				e: *ast::expr => {
+					z += fmt::fprint(out, " else ")?;
+					z += expr(out, indent, *e)?;
+				},
+			};
+			z;
+		},
 		e: ast::list_expr => {
 			let z = fmt::fprintf(out, "{{")?;
 			for (let i = 0z; i < len(e); i += 1) {