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AstGen: implement compile error for useless locals

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When a local variable has an initialization expression of type
'noreturn', emit a compile error. This brings this branch closer
to parity with master branch.
This commit is contained in:
Andrew Kelley 2021-06-25 19:43:01 -07:00
parent 527c55aa56
commit cffa22a658
2 changed files with 32 additions and 2 deletions
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31
src/AstGen.zig
View file

@ -2332,6 +2332,8 @@ fn varDecl(
.ty = try typeExpr(gz, scope, var_decl.ast.type_node), .ty = try typeExpr(gz, scope, var_decl.ast.type_node),
} else .none; } else .none;
const init_inst = try expr(gz, scope, result_loc, var_decl.ast.init_node); const init_inst = try expr(gz, scope, result_loc, var_decl.ast.init_node);
try astgen.checkVarInitExpr(gz.*, node, var_decl.ast.init_node, init_inst, "local constant");
const sub_scope = try block_arena.create(Scope.LocalVal); const sub_scope = try block_arena.create(Scope.LocalVal);
sub_scope.* = .{ sub_scope.* = .{
.parent = scope, .parent = scope,
@ -2382,6 +2384,8 @@ fn varDecl(
} }
const init_result_loc: ResultLoc = .{ .block_ptr = &init_scope }; const init_result_loc: ResultLoc = .{ .block_ptr = &init_scope };
const init_inst = try expr(&init_scope, &init_scope.base, init_result_loc, var_decl.ast.init_node); const init_inst = try expr(&init_scope, &init_scope.base, init_result_loc, var_decl.ast.init_node);
try astgen.checkVarInitExpr(init_scope, node, var_decl.ast.init_node, init_inst, "local constant");
const zir_tags = astgen.instructions.items(.tag); const zir_tags = astgen.instructions.items(.tag);
const zir_datas = astgen.instructions.items(.data); const zir_datas = astgen.instructions.items(.data);
@ -2482,7 +2486,8 @@ fn varDecl(
resolve_inferred_alloc = alloc; resolve_inferred_alloc = alloc;
break :a .{ .alloc = alloc, .result_loc = .{ .inferred_ptr = alloc } }; break :a .{ .alloc = alloc, .result_loc = .{ .inferred_ptr = alloc } };
}; };
_ = try expr(gz, scope, var_data.result_loc, var_decl.ast.init_node); const init_inst = try expr(gz, scope, var_data.result_loc, var_decl.ast.init_node);
try astgen.checkVarInitExpr(gz.*, node, var_decl.ast.init_node, init_inst, "local variable");
if (resolve_inferred_alloc != .none) { if (resolve_inferred_alloc != .none) {
_ = try gz.addUnNode(.resolve_inferred_alloc, resolve_inferred_alloc, node); _ = try gz.addUnNode(.resolve_inferred_alloc, resolve_inferred_alloc, node);
} }
@ -9602,3 +9607,27 @@ fn advanceSourceCursor(astgen: *AstGen, source: []const u8, end: usize) void {
astgen.source_line = line; astgen.source_line = line;
astgen.source_column = column; astgen.source_column = column;
} }
fn checkVarInitExpr(
astgen: *AstGen,
gz: GenZir,
var_node: ast.Node.Index,
init_node: ast.Node.Index,
init_inst: Zir.Inst.Ref,
var_name_text: []const u8,
) !void {
if (gz.refIsNoReturn(init_inst)) {
return astgen.failNodeNotes(
var_node,
"useless {s}",
.{var_name_text},
&[_]u32{
try astgen.errNoteNode(
init_node,
"control flow is diverted here",
.{},
),
},
);
}
}

3
test/compile_errors.zig
View file

@ -4831,7 +4831,8 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
\\ const a = return; \\ const a = return;
\\} \\}
, &[_][]const u8{ , &[_][]const u8{
"tmp.zig:2:5: error: unreachable code", "tmp.zig:2:5: error: useless local constant",
"tmp.zig:2:15: note: control flow is diverted here",
}); });
cases.add("unreachable variable", cases.add("unreachable variable",