remove unreachable code paths from std.zig.Ast.lastToken

This function checks for various possibilities that are never produced
by the parser.
Given that lastToken is unsafe to call on an Ast with errors, I also
removed code paths that would be reachable on an Ast with errors.

1 files changed, 15 insertions, 132 deletions

diff --git a/lib/std/zig/Ast.zig b/lib/std/zig/Ast.zig
index d4503b95ca..9adb8d83bf 100644
--- a/lib/std/zig/Ast.zig
+++ b/lib/std/zig/Ast.zig
@@ -800,7 +800,6 @@ pub fn lastToken(tree: Ast, node: Node.Index) TokenIndex {
     const tags = tree.nodes.items(.tag);
     const datas = tree.nodes.items(.data);
     const main_tokens = tree.nodes.items(.main_token);
-    const token_starts = tree.tokens.items(.start);
     const token_tags = tree.tokens.items(.tag);
     var n = node;
     var end_offset: TokenIndex = 0;
@@ -816,6 +815,7 @@ pub fn lastToken(tree: Ast, node: Node.Index) TokenIndex {
         .@"try",
         .@"await",
         .optional_type,
+        .@"suspend",
         .@"resume",
         .@"nosuspend",
         .@"comptime",
@@ -880,6 +880,9 @@ pub fn lastToken(tree: Ast, node: Node.Index) TokenIndex {
         .for_simple,
         .fn_proto_simple,
         .fn_proto_multi,
+        .fn_proto_one,
+        .fn_proto,
+        .fn_decl,
         .ptr_type_aligned,
         .ptr_type_sentinel,
         .ptr_type,
@@ -928,9 +931,7 @@ pub fn lastToken(tree: Ast, node: Node.Index) TokenIndex {
         .call, .async_call => {
             end_offset += 1; // for the rparen
             const params = tree.extraData(datas[n].rhs, Node.SubRange);
-            if (params.end - params.start == 0) {
-                return main_tokens[n] + end_offset;
-            }
+            assert(params.end - params.start > 0);
             n = tree.extra_data[params.end - 1]; // last parameter
         },
         .tagged_union_enum_tag => {
@@ -1122,48 +1123,28 @@ pub fn lastToken(tree: Ast, node: Node.Index) TokenIndex {
                 n = datas[n].rhs;
             } else {
                 const extra = tree.extraData(datas[n].lhs, Node.LocalVarDecl);
-                if (extra.align_node != 0) {
-                    end_offset += 1; // for the rparen
-                    n = extra.align_node;
-                } else if (extra.type_node != 0) {
-                    n = extra.type_node;
-                } else {
-                    end_offset += 1; // from mut token to name
-                    return main_tokens[n] + end_offset;
-                }
+                assert(extra.align_node != 0);
+                end_offset += 1; // for the rparen
+                n = extra.align_node;
             }
         },
         .container_field_init => {
             if (datas[n].rhs != 0) {
                 n = datas[n].rhs;
-            } else if (datas[n].lhs != 0) {
-                n = datas[n].lhs;
             } else {
-                return main_tokens[n] + end_offset;
+                assert(datas[n].lhs != 0);
+                n = datas[n].lhs;
             }
         },
         .container_field_align => {
-            if (datas[n].rhs != 0) {
-                end_offset += 1; // for the rparen
-                n = datas[n].rhs;
-            } else if (datas[n].lhs != 0) {
-                n = datas[n].lhs;
-            } else {
-                return main_tokens[n] + end_offset;
-            }
+            assert(datas[n].rhs != 0);
+            end_offset += 1; // for the rparen
+            n = datas[n].rhs;
         },
         .container_field => {
             const extra = tree.extraData(datas[n].rhs, Node.ContainerField);
-            if (extra.value_expr != 0) {
-                n = extra.value_expr;
-            } else if (extra.align_expr != 0) {
-                end_offset += 1; // for the rparen
-                n = extra.align_expr;
-            } else if (datas[n].lhs != 0) {
-                n = datas[n].lhs;
-            } else {
-                return main_tokens[n] + end_offset;
-            }
+            assert(extra.value_expr != 0);
+            n = extra.value_expr;
         },
 
         .array_init_one,
@@ -1208,97 +1189,6 @@ pub fn lastToken(tree: Ast, node: Node.Index) TokenIndex {
                 return main_tokens[n] + end_offset;
             }
         },
-        .fn_decl => {
-            if (datas[n].rhs != 0) {
-                n = datas[n].rhs;
-            } else {
-                n = datas[n].lhs;
-            }
-        },
-        .fn_proto_one => {
-            const extra = tree.extraData(datas[n].lhs, Node.FnProtoOne);
-            // addrspace, linksection, callconv, align can appear in any order, so we
-            // find the last one here.
-            var max_node: Node.Index = datas[n].rhs;
-            var max_start = token_starts[main_tokens[max_node]];
-            var max_offset: TokenIndex = 0;
-            if (extra.align_expr != 0) {
-                const start = token_starts[main_tokens[extra.align_expr]];
-                if (start > max_start) {
-                    max_node = extra.align_expr;
-                    max_start = start;
-                    max_offset = 1; // for the rparen
-                }
-            }
-            if (extra.addrspace_expr != 0) {
-                const start = token_starts[main_tokens[extra.addrspace_expr]];
-                if (start > max_start) {
-                    max_node = extra.addrspace_expr;
-                    max_start = start;
-                    max_offset = 1; // for the rparen
-                }
-            }
-            if (extra.section_expr != 0) {
-                const start = token_starts[main_tokens[extra.section_expr]];
-                if (start > max_start) {
-                    max_node = extra.section_expr;
-                    max_start = start;
-                    max_offset = 1; // for the rparen
-                }
-            }
-            if (extra.callconv_expr != 0) {
-                const start = token_starts[main_tokens[extra.callconv_expr]];
-                if (start > max_start) {
-                    max_node = extra.callconv_expr;
-                    max_start = start;
-                    max_offset = 1; // for the rparen
-                }
-            }
-            n = max_node;
-            end_offset += max_offset;
-        },
-        .fn_proto => {
-            const extra = tree.extraData(datas[n].lhs, Node.FnProto);
-            // addrspace, linksection, callconv, align can appear in any order, so we
-            // find the last one here.
-            var max_node: Node.Index = datas[n].rhs;
-            var max_start = token_starts[main_tokens[max_node]];
-            var max_offset: TokenIndex = 0;
-            if (extra.align_expr != 0) {
-                const start = token_starts[main_tokens[extra.align_expr]];
-                if (start > max_start) {
-                    max_node = extra.align_expr;
-                    max_start = start;
-                    max_offset = 1; // for the rparen
-                }
-            }
-            if (extra.addrspace_expr != 0) {
-                const start = token_starts[main_tokens[extra.addrspace_expr]];
-                if (start > max_start) {
-                    max_node = extra.addrspace_expr;
-                    max_start = start;
-                    max_offset = 1; // for the rparen
-                }
-            }
-            if (extra.section_expr != 0) {
-                const start = token_starts[main_tokens[extra.section_expr]];
-                if (start > max_start) {
-                    max_node = extra.section_expr;
-                    max_start = start;
-                    max_offset = 1; // for the rparen
-                }
-            }
-            if (extra.callconv_expr != 0) {
-                const start = token_starts[main_tokens[extra.callconv_expr]];
-                if (start > max_start) {
-                    max_node = extra.callconv_expr;
-                    max_start = start;
-                    max_offset = 1; // for the rparen
-                }
-            }
-            n = max_node;
-            end_offset += max_offset;
-        },
         .while_cont => {
             const extra = tree.extraData(datas[n].rhs, Node.WhileCont);
             assert(extra.then_expr != 0);
@@ -1318,13 +1208,6 @@ pub fn lastToken(tree: Ast, node: Node.Index) TokenIndex {
             const extra = @as(Node.For, @bitCast(datas[n].rhs));
             n = tree.extra_data[datas[n].lhs + extra.inputs + @intFromBool(extra.has_else)];
         },
-        .@"suspend" => {
-            if (datas[n].lhs != 0) {
-                n = datas[n].lhs;
-            } else {
-                return main_tokens[n] + end_offset;
-            }
-        },
         .array_type_sentinel => {
             const extra = tree.extraData(datas[n].rhs, Node.ArrayTypeSentinel);
             n = extra.elem_type;