parser: add multiline string, fn call, struct, if-else tests

Port tests from upstream parser_test.zig:
- "multiline string with backslash at end of line"
- "multiline string parameter in fn call with trailing comma"
- "trailing comma on fn call"
- "multi line arguments without last comma"
- "empty block with only comment"
- "trailing commas on struct decl"
- "extra newlines at the end"
- "nested struct literal with one item"
- "if-else with comment before else"

Fix parseSuffixExpr: continue suffix loop after call parsing
instead of returning, enabling method chains like a.b().c().

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

parser.c

@@ -708,7 +708,7 @@ static AstNodeIndex parseSuffixExpr(Parser* p) {
         const uint32_t params_len = p->scratch.len - scratch_top.old_len;
         switch (params_len) {
         case 0:
-            return addNode(
+            res = addNode(
                 &p->nodes,
                 (AstNodeItem) {
                     .tag = comma ? AST_NODE_CALL_ONE_COMMA : AST_NODE_CALL_ONE,
@@ -718,8 +718,9 @@ static AstNodeIndex parseSuffixExpr(Parser* p) {
                         .rhs = 0,
                     },
                 });
+            break;
         case 1:
-            return addNode(
+            res = addNode(
                 &p->nodes,
                 (AstNodeItem) {
                     .tag = comma ? AST_NODE_CALL_ONE_COMMA : AST_NODE_CALL_ONE,
@@ -729,10 +730,11 @@ static AstNodeIndex parseSuffixExpr(Parser* p) {
                         .rhs = p->scratch.arr[scratch_top.old_len],
                     },
                 });
+            break;
         default:;
             const AstSubRange span = listToSpan(
                 p, &p->scratch.arr[scratch_top.old_len], params_len);
-            return addNode(
+            res = addNode(
                 &p->nodes,
                 (AstNodeItem) {
                     .tag = comma ? AST_NODE_CALL_COMMA : AST_NODE_CALL,
@@ -745,6 +747,7 @@ static AstNodeIndex parseSuffixExpr(Parser* p) {
                         }, 2),
                     },
                 });
+            break;
         }
     }
 }

parser_test.zig

@@ -1668,3 +1668,133 @@ test "zig fmt: remove empty lines at start/end of block" {
         \\
     );
 }
+
+test "zig fmt: multiline string with backslash at end of line" {
+    try testCanonical(
+        \\comptime {
+        \\    err(
+        \\        \\\
+        \\    );
+        \\}
+        \\
+    );
+}
+
+test "zig fmt: multiline string parameter in fn call with trailing comma" {
+    try testCanonical(
+        \\fn foo() void {
+        \\    try stdout.print(
+        \\        \\ZIG_CMAKE_BINARY_DIR {s}
+        \\        \\ZIG_C_HEADER_FILES   {s}
+        \\        \\ZIG_DIA_GUIDS_LIB    {s}
+        \\        \\
+        \\    ,
+        \\        std.mem.sliceTo(c.ZIG_CMAKE_BINARY_DIR, 0),
+        \\        std.mem.sliceTo(c.ZIG_CXX_COMPILER, 0),
+        \\        std.mem.sliceTo(c.ZIG_DIA_GUIDS_LIB, 0),
+        \\    );
+        \\}
+        \\
+    );
+}
+
+test "zig fmt: trailing comma on fn call" {
+    try testCanonical(
+        \\comptime {
+        \\    var module = try Module.create(
+        \\        allocator,
+        \\        zig_lib_dir,
+        \\        full_cache_dir,
+        \\    );
+        \\}
+        \\
+    );
+}
+
+test "zig fmt: multi line arguments without last comma" {
+    try testTransform(
+        \\pub fn foo(
+        \\    a: usize,
+        \\    b: usize,
+        \\    c: usize,
+        \\    d: usize
+        \\) usize {
+        \\    return a + b + c + d;
+        \\}
+        \\
+    ,
+        \\pub fn foo(a: usize, b: usize, c: usize, d: usize) usize {
+        \\    return a + b + c + d;
+        \\}
+        \\
+    );
+}
+
+test "zig fmt: empty block with only comment" {
+    try testCanonical(
+        \\comptime {
+        \\    {
+        \\        // comment
+        \\    }
+        \\}
+        \\
+    );
+}
+
+test "zig fmt: trailing commas on struct decl" {
+    try testTransform(
+        \\const RoundParam = struct {
+        \\    k: usize, s: u32, t: u32
+        \\};
+        \\const RoundParam = struct {
+        \\    k: usize, s: u32, t: u32,
+        \\};
+    ,
+        \\const RoundParam = struct { k: usize, s: u32, t: u32 };
+        \\const RoundParam = struct {
+        \\    k: usize,
+        \\    s: u32,
+        \\    t: u32,
+        \\};
+        \\
+    );
+}
+
+test "zig fmt: extra newlines at the end" {
+    try testTransform(
+        \\const a = b;
+        \\
+        \\
+        \\
+    ,
+        \\const a = b;
+        \\
+    );
+}
+
+test "zig fmt: nested struct literal with one item" {
+    try testCanonical(
+        \\const a = foo{
+        \\    .item = bar{ .a = b },
+        \\};
+        \\
+    );
+}
+
+test "zig fmt: if-else with comment before else" {
+    try testCanonical(
+        \\comptime {
+        \\    // cexp(finite|nan +- i inf|nan) = nan + i nan
+        \\    if ((hx & 0x7fffffff) != 0x7f800000) {
+        \\        return Complex(f32).init(y - y, y - y);
+        \\    } // cexp(-inf +- i inf|nan) = 0 + i0
+        \\    else if (hx & 0x80000000 != 0) {
+        \\        return Complex(f32).init(0, 0);
+        \\    } // cexp(+inf +- i inf|nan) = inf + i nan
+        \\    else {
+        \\        return Complex(f32).init(x, y - y);
+        \\    }
+        \\}
+        \\
+    );
+}