Sema: better source location for incompatible capture group

2 files changed, 42 insertions, 9 deletions

diff --git a/src/Module.zig b/src/Module.zig
index fd8c217bd1..8389dcec19 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -2348,6 +2348,26 @@ pub const SrcLoc = struct {
                     }
                 } else unreachable;
             },
+            .node_offset_switch_prong_capture => |node_off| {
+                const tree = try src_loc.file_scope.getTree(gpa);
+                const case_node = src_loc.declRelativeToNodeIndex(node_off);
+                const node_tags = tree.nodes.items(.tag);
+                const case = switch (node_tags[case_node]) {
+                    .switch_case_one => tree.switchCaseOne(case_node),
+                    .switch_case => tree.switchCase(case_node),
+                    else => unreachable,
+                };
+                const start_tok = case.payload_token.?;
+                const token_tags = tree.tokens.items(.tag);
+                const end_tok = switch (token_tags[start_tok]) {
+                    .asterisk => start_tok + 1,
+                    else => start_tok,
+                };
+                const start = tree.tokens.items(.start)[start_tok];
+                const end_start = tree.tokens.items(.start)[end_tok];
+                const end = end_start + @intCast(u32, tree.tokenSlice(end_tok).len);
+                return Span{ .start = start, .end = end, .main = start };
+            },
             .node_offset_fn_type_align => |node_off| {
                 const tree = try src_loc.file_scope.getTree(gpa);
                 const node_datas = tree.nodes.items(.data);
@@ -2877,6 +2897,9 @@ pub const LazySrcLoc = union(enum) {
     /// range nodes. The error applies to all of them.
     /// The Decl is determined contextually.
     node_offset_switch_range: i32,
+    /// The source location points to the capture of a switch_prong.
+    /// The Decl is determined contextually.
+    node_offset_switch_prong_capture: i32,
     /// The source location points to the align expr of a function type
     /// expression, found by taking this AST node index offset from the containing
     /// Decl AST node, which points to a function type AST node. Next, navigate to
@@ -3017,6 +3040,7 @@ pub const LazySrcLoc = union(enum) {
             .node_offset_switch_operand,
             .node_offset_switch_special_prong,
             .node_offset_switch_range,
+            .node_offset_switch_prong_capture,
             .node_offset_fn_type_align,
             .node_offset_fn_type_addrspace,
             .node_offset_fn_type_section,
@@ -5602,6 +5626,7 @@ pub const SwitchProngSrc = union(enum) {
     scalar: u32,
     multi: Multi,
     range: Multi,
+    multi_capture: u32,
 
     pub const Multi = struct {
         prong: u32,
@@ -5657,6 +5682,9 @@ pub const SwitchProngSrc = union(enum) {
                 .scalar => |i| if (!is_multi and i == scalar_i) return LazySrcLoc.nodeOffset(
                     decl.nodeIndexToRelative(case.ast.values[0]),
                 ),
+                .multi_capture => |i| if (is_multi and i == multi_i) {
+                    return LazySrcLoc{ .node_offset_switch_prong_capture = decl.nodeIndexToRelative(case_node) };
+                },
                 .multi => |s| if (is_multi and s.prong == multi_i) {
                     var item_i: u32 = 0;
                     for (case.ast.values) |item_node| {
diff --git a/src/Sema.zig b/src/Sema.zig
index af44ffcedd..d8a6eddbb6 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -8197,7 +8197,6 @@ fn zirSwitchCapture(
     const switch_info = zir_datas[capture_info.switch_inst].pl_node;
     const switch_extra = sema.code.extraData(Zir.Inst.SwitchBlock, switch_info.payload_index);
     const operand_src: LazySrcLoc = .{ .node_offset_switch_operand = switch_info.src_node };
-    const switch_src = switch_info.src();
     const operand_is_ref = switch_extra.data.bits.is_ref;
     const cond_inst = Zir.refToIndex(switch_extra.data.operand).?;
     const cond_info = sema.code.instructions.items(.data)[cond_inst].un_node;
@@ -8247,7 +8246,7 @@ fn zirSwitchCapture(
             const first_field_index = @intCast(u32, enum_ty.enumTagFieldIndex(first_item_val, sema.mod).?);
             const first_field = union_obj.fields.values()[first_field_index];
 
-            for (items[1..]) |item| {
+            for (items[1..]) |item, i| {
                 const item_ref = try sema.resolveInst(item);
                 // Previous switch validation ensured this will succeed
                 const item_val = sema.resolveConstValue(block, .unneeded, item_ref, undefined) catch unreachable;
@@ -8255,11 +8254,17 @@ fn zirSwitchCapture(
                 const field_index = enum_ty.enumTagFieldIndex(item_val, sema.mod).?;
                 const field = union_obj.fields.values()[field_index];
                 if (!field.ty.eql(first_field.ty, sema.mod)) {
-                    const first_item_src = switch_src; // TODO better source location
-                    const item_src = switch_src;
                     const msg = msg: {
-                        const msg = try sema.errMsg(block, switch_src, "capture group with incompatible types", .{});
+                        const raw_capture_src = Module.SwitchProngSrc{ .multi_capture = capture_info.prong_index };
+                        const capture_src = raw_capture_src.resolve(sema.gpa, sema.mod.declPtr(block.src_decl), switch_info.src_node, .first);
+
+                        const msg = try sema.errMsg(block, capture_src, "capture group with incompatible types", .{});
                         errdefer msg.destroy(sema.gpa);
+
+                        const raw_first_item_src = Module.SwitchProngSrc{ .multi = .{ .prong = capture_info.prong_index, .item = 0 } };
+                        const first_item_src = raw_first_item_src.resolve(sema.gpa, sema.mod.declPtr(block.src_decl), switch_info.src_node, .first);
+                        const raw_item_src = Module.SwitchProngSrc{ .multi = .{ .prong = capture_info.prong_index, .item = 1 + @intCast(u32, i) } };
+                        const item_src = raw_item_src.resolve(sema.gpa, sema.mod.declPtr(block.src_decl), switch_info.src_node, .first);
                         try sema.errNote(block, first_item_src, msg, "type '{}' here", .{first_field.ty.fmt(sema.mod)});
                         try sema.errNote(block, item_src, msg, "type '{}' here", .{field.ty.fmt(sema.mod)});
                         break :msg msg;
@@ -21094,17 +21099,17 @@ const InMemoryCoercionResult = union(enum) {
                     }
                 }
                 if (!actual_noalias) {
-                    try sema.errNote(block, src, msg, "regular paramter {d} cannot cast into a noalias paramter", .{index});
+                    try sema.errNote(block, src, msg, "regular parameter {d} cannot cast into a noalias parameter", .{index});
                 } else {
-                    try sema.errNote(block, src, msg, "noalias paramter {d} cannot cast into a regular paramter", .{index});
+                    try sema.errNote(block, src, msg, "noalias parameter {d} cannot cast into a regular parameter", .{index});
                 }
                 break;
             },
             .fn_param_comptime => |param| {
                 if (param.wanted) {
-                    try sema.errNote(block, src, msg, "non-comptime paramter {d} cannot cast into a comptime paramter", .{param.index});
+                    try sema.errNote(block, src, msg, "non-comptime parameter {d} cannot cast into a comptime parameter", .{param.index});
                 } else {
-                    try sema.errNote(block, src, msg, "comptime paramter {d} cannot cast into a non-comptime paramter", .{param.index});
+                    try sema.errNote(block, src, msg, "comptime parameter {d} cannot cast into a non-comptime parameter", .{param.index});
                 }
                 break;
             },