feat: detect useless parens in binops

bin/tests/data/useless_parens.nix

@@ -1,16 +1,51 @@
 let
   # parens around primitives
-  a = {
+  primitive = {
     b = ("hello");
     c = (d);
     e = ({ f = 2; });
   };
 
   # parens around let-value
-  g = (1 + 2);
-  h = ({ inherit i; });
+  value1 = (1 + 2);
+  value2 = ({ inherit i; });
 
-  # TODO: binary exprs, function args etc.
+  binop =
+    let id = x: x; in
+    (id [3])
+    ++ (id [1] ++ [2])
+  ;
+  binop_no =
+    (1 + 1)
+    * (2 + 2)
+    ;
+
+  # precedence
+  arith1 =
+    4 + (5 * 3)
+    ;
+  arith2 =
+    (4 * 5) / 5
+    ;
+  arith3_no =
+    4 * (5 / 5)
+    ;
+
+  primitive_binop =
+    [1] ++ ([2])
+    ;
+
+  string_concat =
+    (builtins.readFile ./x.txt)
+    + (lib.optionalString true ''
+      foo
+    '')
+    + (lib.optionalString true ''
+      bar
+    '')
+    ;
+
+  # TODO: function args etc.
 in
   # parens around let body
   (null)

bin/tests/snapshots/main__useless_parens_fix.snap

@@ -1,13 +1,14 @@
 ---
 source: bin/tests/main.rs
 expression: "& stdout"
+
 ---
 --- tests/data/useless_parens.nix
 +++ tests/data/useless_parens.nix [fixed]
-@@ -1,16 +1,16 @@
+@@ -1,51 +1,51 @@
  let
    # parens around primitives
-   a = {
+   primitive = {
 -    b = ("hello");
 -    c = (d);
 -    e = ({ f = 2; });
@@ -17,13 +18,60 @@ expression: "& stdout"
    };
 
    # parens around let-value
--  g = (1 + 2);
--  h = ({ inherit i; });
-+  g = 1 + 2;
-+  h = { inherit i; };
+-  value1 = (1 + 2);
+-  value2 = ({ inherit i; });
++  value1 = 1 + 2;
++  value2 = { inherit i; };
 
-   # TODO: binary exprs, function args etc.
+   binop =
+     let id = x: x; in
+-    (id [3])
+-    ++ (id [1] ++ [2])
++    id [3]
++    ++ id [1] ++ [2]
+   ;
+   binop_no =
+     (1 + 1)
+     * (2 + 2)
+     ;
+
+   # precedence
+   arith1 =
+-    4 + (5 * 3)
++    4 + 5 * 3
+     ;
+   arith2 =
+-    (4 * 5) / 5
++    4 * 5 / 5
+     ;
+   arith3_no =
+     4 * (5 / 5)
+     ;
+
+   primitive_binop =
+-    [1] ++ ([2])
++    [1] ++ [2]
+     ;
+
+   string_concat =
+-    (builtins.readFile ./x.txt)
+-    + (lib.optionalString true ''
++    builtins.readFile ./x.txt
++    + lib.optionalString true ''
+       foo
+-    '')
+-    + (lib.optionalString true ''
++    ''
++    + lib.optionalString true ''
+       bar
+-    '')
++    ''
+     ;
+
+   # TODO: function args etc.
  in
    # parens around let body
 -  (null)
 +  null
+
+

bin/tests/snapshots/main__useless_parens_lint.snap

@@ -1,11 +1,12 @@
 ---
 source: bin/tests/main.rs
 expression: "& out"
+
 ---
 [W08] Warning: These parentheses can be omitted
-    ╭─[data/useless_parens.nix:16:3]
+    ╭─[data/useless_parens.nix:51:3]
     │
- 16 │   (null)
+ 51 │   (null)
     ·   ───┬──  
     ·      ╰──── Useless parentheses around body of let expression
 ────╯
@@ -31,16 +32,67 @@ expression: "& out"
    ·               ╰─────── Useless parentheses around value in binding
 ───╯
 [W08] Warning: These parentheses can be omitted
-    ╭─[data/useless_parens.nix:10:7]
+    ╭─[data/useless_parens.nix:10:12]
     │
- 10 │   g = (1 + 2);
-    ·       ───┬───  
-    ·          ╰───── Useless parentheses around value in binding
+ 10 │   value1 = (1 + 2);
+    ·            ───┬───  
+    ·               ╰───── Useless parentheses around value in binding
 ────╯
 [W08] Warning: These parentheses can be omitted
-    ╭─[data/useless_parens.nix:11:7]
+    ╭─[data/useless_parens.nix:11:12]
     │
- 11 │   h = ({ inherit i; });
-    ·       ────────┬───────  
-    ·               ╰───────── Useless parentheses around value in binding
+ 11 │   value2 = ({ inherit i; });
+    ·            ────────┬───────  
+    ·                    ╰───────── Useless parentheses around value in binding
 ────╯
+[W08] Warning: These parentheses can be omitted
+    ╭─[data/useless_parens.nix:15:5]
+    │
+ 15 │     (id [3])
+    ·     ────┬───  
+    ·         ╰───── Useless parentheses in operand of binary operator
+ 16 │     ++ (id [1] ++ [2])
+    ·        ───────┬───────  
+    ·               ╰───────── Useless parentheses in operand of binary operator
+────╯
+[W08] Warning: These parentheses can be omitted
+    ╭─[data/useless_parens.nix:25:9]
+    │
+ 25 │     4 + (5 * 3)
+    ·         ───┬───  
+    ·            ╰───── Useless parentheses in operand of binary operator
+────╯
+[W08] Warning: These parentheses can be omitted
+    ╭─[data/useless_parens.nix:28:5]
+    │
+ 28 │     (4 * 5) / 5
+    ·     ───┬───  
+    ·        ╰───── Useless parentheses in operand of binary operator
+────╯
+[W08] Warning: These parentheses can be omitted
+    ╭─[data/useless_parens.nix:35:12]
+    │
+ 35 │     [1] ++ ([2])
+    ·            ──┬──  
+    ·              ╰──── Useless parentheses around primitive expression
+────╯
+[W08] Warning: These parentheses can be omitted
+    ╭─[data/useless_parens.nix:43:7]
+    │
+ 43 │ ╭─▶     + (lib.optionalString true ''
+ 45 │ ├─▶     '')
+    · │             
+    · ╰───────────── Useless parentheses in operand of binary operator
+────╯
+[W08] Warning: These parentheses can be omitted
+    ╭─[data/useless_parens.nix:39:5]
+    │
+ 39 │         (builtins.readFile ./x.txt)
+    ·         ─────────────┬─────────────  
+    ·                      ╰─────────────── Useless parentheses in operand of binary operator
+ 40 │ ╭─▶     + (lib.optionalString true ''
+ 42 │ ├─▶     '')
+    · │             
+    · ╰───────────── Useless parentheses in operand of binary operator
+────╯
+