Diagnose named-but-unused local variables

This is a case of losing a non-discarded value that wasn't being covered with the discarding rule.

I think I like this... although I had to update unused dummy variables in the tests to rename them to `_`, it caught a few cases where I had a loop `counter` variable I wasn't actually using that was just a leftover from a previous incarnation of the test, so I could and did remove it.

Author: hsutter

regression-tests/mixed-lifetime-safety-pointer-init-1-error.cpp2

@@ -15,8 +15,9 @@ main: () -> int = {
     }
 
     print_and_decorate( p* );
+    print_and_decorate( x );
 }
 
-print_and_decorate: (thing:_) =
+print_and_decorate: (thing) =
     std::cout << ">> " << thing << "\n";
 

regression-tests/mixed-lifetime-safety-pointer-init-2-error.cpp2

@@ -15,8 +15,9 @@ main: () -> int = {
     }
 
     print_and_decorate( p* );
+    print_and_decorate( x );
 }
 
-print_and_decorate: (thing:_) =
+print_and_decorate: (thing) =
     std::cout << ">> " << thing << "\n";
 

regression-tests/mixed-lifetime-safety-pointer-init-3-error.cpp2

@@ -15,8 +15,9 @@ main: () -> int = {
     }
 
     print_and_decorate( p* );
+    print_and_decorate( x );
 }
 
-print_and_decorate: (thing:_) =
+print_and_decorate: (thing) =
     std::cout << ">> " << thing << "\n";
 

regression-tests/mixed-out-destruction.cpp2

@@ -19,16 +19,16 @@ struct C {
 
 //-------------------------------------------------------
 // 0x: Test one level of out and immediate throw
-f00: ()         throws = { c:C="f00";  x: X;  f01(out x); }
-f01: (out x: X) throws = { c:C="f01";  x=();  throw_1();  }
+f00: ()         throws = { _:C="f00";  x: X;  f01(out x); }
+f01: (out x: X) throws = { _:C="f01";  x=();  throw_1();  }
 
 //-------------------------------------------------------
 // 1x: Test multiple levels of out and intermediate throw
-f10: ()         throws = { c:C="f10";  x: X;  f11(out x); }
-f11: (out x: X) throws = { c:C="f11";         f12(out x); }
-f12: (out x: X) throws = { c:C="f12";         f13(out x);  throw_1(); }
-f13: (out x: X) throws = { c:C="f13";         f14(out x); }
-f14: (out x: X) throws = { c:C="f14";  x=();  }
+f10: ()         throws = { _:C="f10";  x: X;  f11(out x); }
+f11: (out x: X) throws = { _:C="f11";         f12(out x); }
+f12: (out x: X) throws = { _:C="f12";         f13(out x);  throw_1(); }
+f13: (out x: X) throws = { _:C="f13";         f14(out x); }
+f14: (out x: X) throws = { _:C="f14";  x=();  }
 
 int main() {
     C c("main");

regression-tests/pure2-break-continue.cpp2

@@ -160,8 +160,7 @@ do_break_outer: () =
 for_continue_inner: () =
 {
     vi: std::vector = ( 0, 1, 2 );
-    counter := 0;
-    for vi next counter++ do (i) {
+    for vi do (i) {
         vj: std::vector = ( 0, 1, 2 );
         inner: for vj do (j) {
             std::cout << i << j << " ";
@@ -178,8 +177,7 @@ for_continue_inner: () =
 for_continue_outer: () =
 {
     vi: std::vector = ( 0, 1, 2 );
-    counter := 0;
-    outer: for vi next counter++ do (i) {
+    outer: for vi do (i) {
         vj: std::vector = ( 0, 1, 2 );
         for vj do (j) {
             std::cout << i << j << " ";
@@ -196,8 +194,7 @@ for_continue_outer: () =
 for_break_inner: () =
 {
     vi: std::vector = ( 0, 1, 2 );
-    counter := 0;
-    for vi next counter++ do (i) {
+    for vi do (i) {
         vj: std::vector = ( 0, 1, 2 );
         inner: for vj do (j) {
             std::cout << i << j << " ";
@@ -214,8 +211,7 @@ for_break_inner: () =
 for_break_outer: () =
 {
     vi: std::vector = ( 0, 1, 2 );
-    counter := 0;
-    outer: for vi next counter++ do (i) {
+    outer: for vi do (i) {
         vj: std::vector = ( 0, 1, 2 );
         for vj do (j) {
             std::cout << i << j << " ";

regression-tests/pure2-deducing-pointers-error.cpp2

@@ -38,6 +38,7 @@ main: () -> int = {
     fp = 0;       // caught
 
     f := fun(a)*;
+    _ = f;
 
     fp2 := fun2(a).result;
     fp2--;        // not caught :(

regression-tests/pure2-lifetime-safety-pointer-init-1-error.cpp2

@@ -12,8 +12,9 @@ main: () -> int = {
     }
 
     print_and_decorate( p* );
+    print_and_decorate( x );
 }
 
-print_and_decorate: (thing:_) =
+print_and_decorate: (thing) =
     std::cout << ">> " << thing << "\n";
 

regression-tests/pure2-look-up-parameter-across-unnamed-function.cpp2

@@ -2,13 +2,15 @@
 f: () -> (ri : int = 0) = {
     pred := :(e) e == 1;
     ri = 42;
+    pred(ri);
     // "return;" is implicit"
 }
 
 g: () -> (ri : int) = {
     ri = 0;
     pred := :(e) e == 1;
     ri = 42;
+    pred(ri);
     return;
 }
 

regression-tests/pure2-more-wildcards.cpp2

@@ -6,6 +6,7 @@ main: () -> int
     x: const   _ = 2;
     p: *       _ = x&;
     q: * const _ = p&;
+    assert (q);
 
     if x is (less_than(20)) {
         std::cout << "yes, less\n";

regression-tests/pure2-requires-clauses.cpp2

@@ -18,6 +18,6 @@ f:  <T: type, U: type>
 v: <T> const T requires std::same_as<T, i32> = 0;
 
 main: () = {
-    x: X<int,int> = ();
+    _: X<int,int> = ();
     std::cout << f<int,int>(2,5);
 }

regression-tests/pure2-types-basics.cpp2

@@ -71,9 +71,9 @@ main: () = {
     std::cout << "f2: (x.f2(2,2))$\n";
     std::cout << "f3: (x.f3<3,3>())$\n";
     std::cout << "f4: (x.f4<4,4>())$\n";
-    x2: N::myclass = "abracadabra";
-    x3: N::myclass = ();
-    x4: N::myclass = (1, "hair");
+    _: N::myclass = "abracadabra";
+    _: N::myclass = ();
+    _: N::myclass = (1, "hair");
 
     // Invoke the single-param operator=s as actual assignments
     std::cout << "x's state before assignments: ";

regression-tests/pure2-types-ordering-via-meta-functions.cpp2

@@ -46,5 +46,5 @@ main: () = {
         std::cout << "more\n";
     }
 
-    s: mystruct = ();
+    _: mystruct = ();
 }

regression-tests/pure2-ufcs-member-access-and-chaining.cpp2

@@ -19,6 +19,8 @@ main: () -> int = {
     _ = (j.i).ufcs();
 
     42.no_return();
+
+    res.no_return();
 }
 
 no_return: (_) = { }

regression-tests/pure2-variadics.cpp2

@@ -19,7 +19,7 @@ make:     <T, Args...> (forward args...: Args)  :T = args...;
 
 main: ()
 = {
-    a: x<int, long, std::string> = ();
+    _: x<int, long, std::string> = ();
 
     std::cout << std::string("xyzzy", 3) << "\n";
     std::cout << make_string("plugh", :u8=3) << "\n";

regression-tests/pure2-various-string-literals.cpp2

@@ -8,4 +8,13 @@ main: () = {
     s7 := u8R"(u8R")";
     s8 := UR"(UR")";
     s9 := LR"(LR")";
+    _ = s1;
+    _ = s2;
+    _ = s3;
+    _ = s4;
+    _ = s5;
+    _ = s6;
+    _ = s7;
+    _ = s8;
+    _ = s9;
 }

regression-tests/test-results/mixed-out-destruction.cpp

@@ -54,13 +54,13 @@ int main() {
 
 
 #line 22 "mixed-out-destruction.cpp2"
-auto f00() -> void     {   C c {"f00"}; cpp2::deferred_init<X> x; f01(cpp2::out(&x));}
-auto f01(cpp2::out<X> x) -> void{C c {"f01"}; x.construct();throw_1();}
+auto f00() -> void     {   C auto_22_28 {"f00"}; cpp2::deferred_init<X> x; f01(cpp2::out(&x));}
+auto f01(cpp2::out<X> x) -> void{C auto_23_28 {"f01"}; x.construct();throw_1();}
 
 #line 27 "mixed-out-destruction.cpp2"
-auto f10() -> void     {   C c {"f10"}; cpp2::deferred_init<X> x; f11(cpp2::out(&x));}
-auto f11(cpp2::out<X> x) -> void{C c {"f11"}; f12(cpp2::out(&x));}
-auto f12(cpp2::out<X> x) -> void{C c {"f12"}; f13(cpp2::out(&x));throw_1();}
-auto f13(cpp2::out<X> x) -> void{C c {"f13"}; f14(cpp2::out(&x));}
-auto f14(cpp2::out<X> x) -> void{C c {"f14"}; x.construct();}
+auto f10() -> void     {   C auto_27_28 {"f10"}; cpp2::deferred_init<X> x; f11(cpp2::out(&x));}
+auto f11(cpp2::out<X> x) -> void{C auto_28_28 {"f11"}; f12(cpp2::out(&x));}
+auto f12(cpp2::out<X> x) -> void{C auto_29_28 {"f12"}; f13(cpp2::out(&x));throw_1();}
+auto f13(cpp2::out<X> x) -> void{C auto_30_28 {"f13"}; f14(cpp2::out(&x));}
+auto f14(cpp2::out<X> x) -> void{C auto_31_28 {"f14"}; x.construct();}
 

regression-tests/test-results/pure2-break-continue.cpp

@@ -41,13 +41,13 @@ auto do_break_outer() -> void;
 #line 160 "pure2-break-continue.cpp2"
 auto for_continue_inner() -> void;
 
-#line 178 "pure2-break-continue.cpp2"
+#line 177 "pure2-break-continue.cpp2"
 auto for_continue_outer() -> void;
 
-#line 196 "pure2-break-continue.cpp2"
+#line 194 "pure2-break-continue.cpp2"
 auto for_break_inner() -> void;
 
-#line 214 "pure2-break-continue.cpp2"
+#line 211 "pure2-break-continue.cpp2"
 auto for_break_outer() -> void;
 
 
@@ -252,84 +252,80 @@ auto do_break_outer() -> void
 auto for_continue_inner() -> void
 {
     std::vector vi {0, 1, 2}; 
-    auto counter {0}; 
-    for ( auto const& i : vi )  { do {
+    for ( auto const& i : vi ) {
         std::vector vj {0, 1, 2}; 
         for ( auto const& j : vj ) {
-#line 166 "pure2-break-continue.cpp2"
+#line 165 "pure2-break-continue.cpp2"
         {
             std::cout << i << j << " ";
             if (j == 1) {
-                goto CONTINUE_166_9;
+                goto CONTINUE_165_9;
             }
             std::cout << "inner ";
-        } CPP2_CONTINUE_BREAK(166_9) }
+        } CPP2_CONTINUE_BREAK(165_9) }
 
-#line 174 "pure2-break-continue.cpp2"
+#line 173 "pure2-break-continue.cpp2"
         std::cout << "outer ";
-    } while (false); ++counter; }
+    }
 }
 
 auto for_continue_outer() -> void
 {
     std::vector vi {0, 1, 2}; 
-    auto counter {0}; 
     for ( auto const& i : vi ) {
-#line 182 "pure2-break-continue.cpp2"
-     { do {
+#line 180 "pure2-break-continue.cpp2"
+    {
         std::vector vj {0, 1, 2}; 
         for ( auto const& j : vj ) {
             std::cout << i << j << " ";
             if (j == 1) {
-                goto CONTINUE_182_5;
+                goto CONTINUE_180_5;
             }
             std::cout << "inner ";
         }
 
         std::cout << "outer ";
-    } while (false); ++counter; } CPP2_CONTINUE_BREAK(182_5) }
-#line 194 "pure2-break-continue.cpp2"
+    } CPP2_CONTINUE_BREAK(180_5) }
+#line 192 "pure2-break-continue.cpp2"
 }
 
 auto for_break_inner() -> void
 {
     std::vector vi {0, 1, 2}; 
-    auto counter {0}; 
-    for ( auto const& i : vi )  { do {
+    for ( auto const& i : vi ) {
         std::vector vj {0, 1, 2}; 
         for ( auto const& j : vj ) {
-#line 202 "pure2-break-continue.cpp2"
+#line 199 "pure2-break-continue.cpp2"
         {
             std::cout << i << j << " ";
             if (j == 1) {
-                goto BREAK_202_9;
+                goto BREAK_199_9;
             }
             std::cout << "inner ";
-        } CPP2_CONTINUE_BREAK(202_9) }
+        } CPP2_CONTINUE_BREAK(199_9) }
 
-#line 210 "pure2-break-continue.cpp2"
+#line 207 "pure2-break-continue.cpp2"
         std::cout << "outer ";
-    } while (false); ++counter; }
+    }
 }
 
 auto for_break_outer() -> void
 {
     std::vector vi {0, 1, 2}; 
-    auto counter {0}; 
     for ( auto const& i : vi ) {
-#line 218 "pure2-break-continue.cpp2"
-     { do {
+#line 214 "pure2-break-continue.cpp2"
+    {
         std::vector vj {0, 1, 2}; 
         for ( auto const& j : vj ) {
             std::cout << i << j << " ";
             if (j == 1) {
-                goto BREAK_218_5;
+                goto BREAK_214_5;
             }
             std::cout << "inner ";
         }
 
         std::cout << "outer ";
-    } while (false); ++counter; } CPP2_CONTINUE_BREAK(218_5) }
-#line 230 "pure2-break-continue.cpp2"
+    } CPP2_CONTINUE_BREAK(214_5) }
+#line 226 "pure2-break-continue.cpp2"
 }
 

regression-tests/test-results/pure2-look-up-parameter-across-unnamed-function.cpp

@@ -18,11 +18,11 @@ struct f_ret { int ri; };
 
 
 
-#line 8 "pure2-look-up-parameter-across-unnamed-function.cpp2"
+#line 9 "pure2-look-up-parameter-across-unnamed-function.cpp2"
 [[nodiscard]] auto g() -> g_ret;
 
 
-#line 15 "pure2-look-up-parameter-across-unnamed-function.cpp2"
+#line 17 "pure2-look-up-parameter-across-unnamed-function.cpp2"
 [[nodiscard]] auto main() -> int;
 
 
@@ -35,15 +35,17 @@ struct f_ret { int ri; };
 #line 3 "pure2-look-up-parameter-across-unnamed-function.cpp2"
     auto pred {[](auto const& e) -> auto { return e == 1;  }}; 
     ri = 42;
+    std::move(pred)(ri);
     return  { std::move(ri) }; // "return;" is implicit"
 }
 
 [[nodiscard]] auto g() -> g_ret{
         cpp2::deferred_init<int> ri;
-#line 9 "pure2-look-up-parameter-across-unnamed-function.cpp2"
+#line 10 "pure2-look-up-parameter-across-unnamed-function.cpp2"
     ri.construct(0);
     auto pred {[](auto const& e) -> auto { return e == 1;  }}; 
     ri.value() = 42;
+    std::move(pred)(ri.value());
     return  { std::move(ri.value()) }; 
 }
 

regression-tests/test-results/pure2-more-wildcards.cpp

@@ -28,6 +28,7 @@
     auto const x {2}; 
     auto* p {&x}; 
     auto const* q {&p}; 
+    cpp2::Default.expects(std::move(q), "");
 
     if (cpp2::is(x, (less_than(20)))) {
         std::cout << "yes, less\n";

regression-tests/test-results/pure2-requires-clauses.cpp

@@ -67,7 +67,7 @@ requires (std::same_as<T,cpp2::i32>)
 T const v {0}; 
 
 auto main() -> int{
-    X<int,int> x {}; 
+    X<int,int> auto_21_5 {}; 
     std::cout << f<int,int>(2, 5);
 }