Detect unused variables

ui-tests/asm/drop.nil

@@ -1,6 +1,6 @@
 //@check-pass
 
-function dropping(a: I32) =
+function dropping(_a: I32) =
     ___asm(
         __locals(),
         "local.get 0",

ui-tests/asm/instr_not_string.nil

@@ -1,4 +1,4 @@
-function a(a: I32) =
+function a(_a: I32) =
     ___asm(
         __locals(),
         0,

ui-tests/asm/invalid_instr.nil

@@ -1,4 +1,4 @@
-function dropping(a: I32) =
+function dropping(_a: I32) =
     ___asm(
         __locals(),
         "meow meow",

ui-tests/asm/missing_locals.nil

@@ -1,4 +1,4 @@
-function dropping(a: I32) =
+function dropping(_a: I32) =
     ___asm(
         "local.get 0",
         "drop",

ui-tests/asm/not_toplevel.nil

@@ -1,4 +1,4 @@
-function dropping(a: I32) = (
+function dropping(_a: I32) = (
     1;
     ___asm(__locals(), "drop");
 );

ui-tests/asm/wrong_imm.nil

@@ -1,11 +1,11 @@
-function a(a: I32) =
+function a(_a: I32) =
     ___asm(
         __locals(),
         "local.get 0 0",
         "drop",
     );
 
-function b(a: I32) =
+function b(_a: I32) =
     ___asm(
         __locals(),
         "local.get",

ui-tests/basic_recovery.stderr

@@ -10,3 +10,11 @@ error: cannot assign String to Int
  --> $DIR/basic_recovery.nil:3
 3 |   let b: Int = "";
           ^
+warning: unused variable: `a`
+ --> $DIR/basic_recovery.nil:2
+2 |   let a: Int = "";
+          ^
+warning: unused variable: `b`
+ --> $DIR/basic_recovery.nil:3
+3 |   let b: Int = "";
+          ^

ui-tests/functions/function_calls_ok.nil

@@ -5,14 +5,14 @@ function main() = (
     singleArg("hi!");
     manyArgs(1,2,3,4,5,6);
 
-    let a: () = returnNothing();
-    let b: () = returnExplicitUnit();
-    let c: String = returnString();
+    let _a: () = returnNothing();
+    let _b: () = returnExplicitUnit();
+    let _c: String = returnString();
 );
 
 function noArgs() =;
-function singleArg(a: String) =;
-function manyArgs(a: Int, b: Int, c: Int, d: Int, e: Int, f: Int) =;
+function singleArg(_a: String) =;
+function manyArgs(_a: Int, _b: Int, _c: Int, _d: Int, _e: Int, _f: Int) =;
 
 function returnNothing() =;
 function returnExplicitUnit(): () =;

ui-tests/functions/missing_args.nil

@@ -2,4 +2,4 @@ function main() = (
     x();
 );
 
-function x(a: Int) = ;
+function x(_a: Int) = ;

ui-tests/lint/unused_vars.nil

@@ -0,0 +1,22 @@
+//@check-pass
+
+function main() = (
+  let x = 0;
+  let _ok = 0;
+  let used = 0;
+
+  used;
+);
+
+function x() = (
+  let x = 0;
+  (
+    let x = 0;
+    call(x);
+  );
+  let y = x;
+);
+
+function call(_a: Int) = ;
+
+function param(p: Int) = ;

ui-tests/lint/unused_vars.stderr

@@ -0,0 +1,12 @@
+warning: unused variable: `x`
+ --> $DIR/unused_vars.nil:4
+4 |   let x = 0;
+          ^
+warning: unused variable: `y`
+ --> $DIR/unused_vars.nil:17
+17 |   let y = x;
+           ^
+warning: unused function parameter: `p`
+ --> $DIR/unused_vars.nil:22
+22 | function param(p: Int) = ;
+                    ^

ui-tests/type/generics/generics_on_primitive.stderr

@@ -2,3 +2,7 @@ error: type I32 does not take any generic arguments but 1 were passed
  --> $DIR/generics_on_primitive.nil:2
 2 |     let a: I32[I32] = 0;
                ^^^
+warning: unused variable: `a`
+ --> $DIR/generics_on_primitive.nil:2
+2 |     let a: I32[I32] = 0;
+            ^

ui-tests/type/generics/generics_structs_in_args.stderr

@@ -0,0 +1,12 @@
+warning: unused function parameter: `a`
+ --> $DIR/generics_structs_in_args.nil:11
+11 | function test(a: A[I32], b: B[I32, Int, I32], c: C) = ;
+                   ^
+warning: unused function parameter: `b`
+ --> $DIR/generics_structs_in_args.nil:11
+11 | function test(a: A[I32], b: B[I32, Int, I32], c: C) = ;
+                              ^
+warning: unused function parameter: `c`
+ --> $DIR/generics_structs_in_args.nil:11
+11 | function test(a: A[I32], b: B[I32, Int, I32], c: C) = ;
+                                                   ^

ui-tests/type/generics/structs.stderr

@@ -0,0 +1,12 @@
+warning: unused function parameter: `a`
+ --> $DIR/structs.nil:9
+9 | function test(a: A[I32], b: B[I32, Int, I32], c: C) = ;
+                  ^
+warning: unused function parameter: `b`
+ --> $DIR/structs.nil:9
+9 | function test(a: A[I32], b: B[I32, Int, I32], c: C) = ;
+                             ^
+warning: unused function parameter: `c`
+ --> $DIR/structs.nil:9
+9 | function test(a: A[I32], b: B[I32, Int, I32], c: C) = ;
+                                                  ^

ui-tests/type/generics/wrong_amount.stderr

@@ -22,3 +22,51 @@ error: type () does not take any generic arguments but 1 were passed
  --> $DIR/wrong_amount.nil:22
 22 |     c3: C[I32],
              ^
+warning: unused function parameter: `a1`
+ --> $DIR/wrong_amount.nil:9
+9 |     a1: A,
+        ^^
+warning: unused function parameter: `a2`
+ --> $DIR/wrong_amount.nil:10
+10 |     a2: A[],
+         ^^
+warning: unused function parameter: `a3`
+ --> $DIR/wrong_amount.nil:11
+11 |     a3: A[I32],
+         ^^
+warning: unused function parameter: `a4`
+ --> $DIR/wrong_amount.nil:12
+12 |     a4: A[I32, I32],
+         ^^
+warning: unused function parameter: `b1`
+ --> $DIR/wrong_amount.nil:14
+14 |     b1: B,
+         ^^
+warning: unused function parameter: `b2`
+ --> $DIR/wrong_amount.nil:15
+15 |     b2: B[],
+         ^^
+warning: unused function parameter: `b3`
+ --> $DIR/wrong_amount.nil:16
+16 |     b3: B[Int, Int],
+         ^^
+warning: unused function parameter: `b4`
+ --> $DIR/wrong_amount.nil:17
+17 |     b4: B[Int, I32, Int],
+         ^^
+warning: unused function parameter: `b5`
+ --> $DIR/wrong_amount.nil:18
+18 |     b5: B[Int, Int, Int, Int],
+         ^^
+warning: unused function parameter: `c1`
+ --> $DIR/wrong_amount.nil:20
+20 |     c1: C,
+         ^^
+warning: unused function parameter: `c2`
+ --> $DIR/wrong_amount.nil:21
+21 |     c2: C[],
+         ^^
+warning: unused function parameter: `c3`
+ --> $DIR/wrong_amount.nil:22
+22 |     c3: C[I32],
+         ^^

ui-tests/type/type_alias.stderr

@@ -0,0 +1,4 @@
+warning: unused variable: `a`
+ --> $DIR/type_alias.nil:6
+6 |     let a: A = (0, 0);
+            ^

ui-tests/type/type_assignments.stderr

@@ -0,0 +1,24 @@
+warning: unused variable: `a1`
+ --> $DIR/type_assignments.nil:15
+15 |     let a1: Int = a;
+             ^^
+warning: unused variable: `b1`
+ --> $DIR/type_assignments.nil:16
+16 |     let b1: I32 = b;
+             ^^
+warning: unused variable: `c1`
+ --> $DIR/type_assignments.nil:17
+17 |     let c1: String = c;
+             ^^
+warning: unused variable: `d1`
+ --> $DIR/type_assignments.nil:18
+18 |     let d1: Bool = d;
+             ^^
+warning: unused variable: `e1`
+ --> $DIR/type_assignments.nil:19
+19 |     let e1: CustomType = e;
+             ^^
+warning: unused variable: `f1`
+ --> $DIR/type_assignments.nil:20
+20 |     let f1: (Int, I32) = f;
+             ^^