Commit 75f7a8913eb6c22a7d2d4514512adb6ef535bb47 | zig

author	Jacob G-W <jacoblevgw@gmail.com> 2021-06-08 20:32:44-04:00
committer	Andrew Kelley <andrew@ziglang.org> 2021-06-21 17:03:02-07:00
log	75f7a8913eb6c22a7d2d4514512adb6ef535bb47
tree	36700c31f1ee628858956753b89eb0bb66a2916b
parent	8a6de78e0787015153707361a58659834d4c39c2

stage2 astgen: find unused vars

2 files changed, 53 insertions(+), 1 deletions(-)

src
- AstGen.zig
test
- stage2
  - test.zig

src/AstGen.zig+45-1

 @@ -1826,6 +1826,7 @@ fn blockExprStmts(
     }
     try genDefers(gz, parent_scope, scope, .none);
+    try checkUsed(gz, parent_scope, scope);
 }
 fn unusedResultExpr(gz: *GenZir, scope: *Scope, statement: ast.Node.Index) InnerError!void {
 @@ -2154,6 +2155,36 @@ fn genDefers(
     }
 }
+fn checkUsed(
+    gz: *GenZir,
+    outer_scope: *Scope,
+    inner_scope: *Scope,
+) InnerError!void {
+    const astgen = gz.astgen;
+    const tree = astgen.tree;
+    const node_datas = tree.nodes.items(.data);
+    var scope = inner_scope;
+    while (scope != outer_scope) {
+        switch (scope.tag) {
+            .gen_zir => scope = scope.cast(GenZir).?.parent,
+            .local_val => {
+                const s = scope.cast(Scope.LocalVal).?;
+                if (!s.used) return astgen.failTok(s.token_src, "unused local constant", .{});
+                scope = s.parent;
+            },
+            .local_ptr => {
+                const s = scope.cast(Scope.LocalPtr).?;
+                if (!s.used) return astgen.failTok(s.token_src, "unused local variable", .{});
+                scope = s.parent;
+            },
+            .defer_normal, .defer_error => scope = scope.cast(Scope.Defer).?.parent,
+            .namespace => unreachable,
+            .top => unreachable,
+        }
+    }
+}
 fn deferStmt(
     gz: *GenZir,
     scope: *Scope,
 @@ -2930,6 +2961,7 @@ fn fnDecl(
                     .name = param_name,
                     .inst = arg_inst,
                     .token_src = name_token,
+                    // TODO make function paramater have different message instead of unused constant
                 };
                 params_scope = &sub_scope.base;
 @@ -3370,6 +3402,7 @@ fn structDeclInner(
     };
     defer block_scope.instructions.deinit(gpa);
+    // TODO should we change this to scope in other places too?
     var namespace: Scope.Namespace = .{ .parent = scope };
     defer namespace.decls.deinit(gpa);
 @@ -6131,10 +6164,14 @@ fn identifier(
         while (true) switch (s.tag) {
             .local_val => {
                 const local_val = s.cast(Scope.LocalVal).?;
+                if (local_val.name == name_str_index) {
+                    local_val.used = true;
+                }
                 if (hit_namespace) {
                     // captures of non-locals need to be emitted as decl_val or decl_ref
                     // This *might* be capturable depending on if it is comptime known
-                    break;
+                    s = local_val.parent;
+                    continue;
                 }
                 if (local_val.name == name_str_index) {
                     return rvalue(gz, scope, rl, local_val.inst, ident);
 @@ -6144,6 +6181,7 @@ fn identifier(
             .local_ptr => {
                 const local_ptr = s.cast(Scope.LocalPtr).?;
                 if (local_ptr.name == name_str_index) {
+                    local_ptr.used = true;
                     if (hit_namespace) {
                         if (local_ptr.is_comptime)
                             break
 @@ -6151,6 +6189,8 @@ fn identifier(
                             return astgen.failNodeNotes(ident, "'{s}' not accessible from inner function", .{ident_name}, &.{
                                 try astgen.errNoteTok(local_ptr.token_src, "declared here", .{}),
                                 // TODO add crossed function definition here note.
+                                // Maybe add a note to the error about it being because of the var,
+                                // maybe recommend copying it into a const variable. -SpexGuy
                             });
                     }
                     switch (rl) {
 @@ -8341,6 +8381,8 @@ const Scope = struct {
         token_src: ast.TokenIndex,
         /// String table index.
         name: u32,
+        /// has this variable been referenced?
+        used: bool = false,
     };
     /// This could be a `const` or `var` local. It has a pointer instead of a value.
 @@ -8358,6 +8400,8 @@ const Scope = struct {
         /// String table index.
         name: u32,
         is_comptime: bool,
+        /// has this variable been referenced?
+        used: bool = false,
     };
     const Defer = struct {

test/stage2/test.zig+8

...	@@ -246,6 +246,14 @@ pub fn addCases(ctx: *TestContext) !void {	...	@@ -246,6 +246,14 @@ pub fn addCases(ctx: *TestContext) !void {
246	"",	246	"",
247	);	247	);
248	}	248	}
		249	{
		250	var case = ctx.exe("unused vars", linux_x64);
		251	case.addError(
		252	\\pub fn main() void {
		253	\\ const x = 1;
		254	\\}
		255	, &.{":2:11: error: unused local constant"});
		256	}
249	{	257	{
250	var case = ctx.exe("@TypeOf", linux_x64);	258	var case = ctx.exe("@TypeOf", linux_x64);
251	case.addCompareOutput(	259	case.addCompareOutput(