compress numerical expressions (#1513)

safe operations
- `a === b` => `a == b`
- `a + -b`  => `a - b`
- `-a + b`  => `b - a`
- `a+ +b`   => `+b+a`

associative operations
(bit-wise operations are safe, otherwise `unsafe_math`)
- `a + (b + c)`       => `(a + b) + c`
- `(n + 2) + 3`       => `5 + n`
- `(2 * n) * 3`       => `6 * n`
- `(a | 1) | (2 | d)` => `(3 | a) | b`

fixes #412

1 files changed, 136 insertions, 0 deletions

diff --git a/test/compress/numbers.js b/test/compress/numbers.js
index 8e32ad02..0b40bb9c 100644
--- a/test/compress/numbers.js
+++ b/test/compress/numbers.js
@@ -17,3 +17,139 @@ hex_numbers_in_parentheses_for_prototype_functions: {
     }
     expect_exact: "-2;(-2).toFixed(0);2;2..toFixed(0);.2;.2.toFixed(0);2e-8;2e-8.toFixed(0);0xde0b6b3a7640080;(0xde0b6b3a7640080).toFixed(0);"
 }
+
+comparisons: {
+    options = {
+        comparisons: true,
+    }
+    input: {
+        console.log(
+            ~x === 42,
+            x % n === 42
+        );
+    }
+    expect: {
+        console.log(
+            42 == ~x,
+            x % n == 42
+        );
+    }
+}
+
+evaluate_1: {
+    options = {
+        evaluate: true,
+        unsafe_math: false,
+    }
+    input: {
+        console.log(
+            x + 1 + 2,
+            x * 1 * 2,
+            +x + 1 + 2,
+            1 + x + 2 + 3,
+            1 | x | 2 | 3,
+            1 + x-- + 2 + 3,
+            1 + (x*y + 2) + 3,
+            1 + (2 + x + 3),
+            1 + (2 + ~x + 3),
+            -y + (2 + ~x + 3),
+            1 & (2 & x & 3),
+            1 + (2 + (x |= 0) + 3)
+        );
+    }
+    expect: {
+        console.log(
+            x + 1 + 2,
+            1 * x * 2,
+            +x + 1 + 2,
+            1 + x + 2 + 3,
+            3 | x,
+            1 + x-- + 2 + 3,
+            x*y + 2 + 1 + 3,
+            1 + (2 + x + 3),
+            2 + ~x + 3 + 1,
+            -y + (2 + ~x + 3),
+            0 & x,
+            2 + (x |= 0) + 3 + 1
+        );
+    }
+}
+
+evaluate_2: {
+    options = {
+        evaluate: true,
+        unsafe_math: true,
+    }
+    input: {
+        console.log(
+            x + 1 + 2,
+            x * 1 * 2,
+            +x + 1 + 2,
+            1 + x + 2 + 3,
+            1 | x | 2 | 3,
+            1 + x-- + 2 + 3,
+            1 + (x*y + 2) + 3,
+            1 + (2 + x + 3),
+            1 & (2 & x & 3),
+            1 + (2 + (x |= 0) + 3)
+        );
+    }
+    expect: {
+        console.log(
+            x + 1 + 2,
+            2 * x,
+            3 + +x,
+            1 + x + 2 + 3,
+            3 | x,
+            6 + x--,
+            6 + x*y,
+            1 + (2 + x + 3),
+            0 & x,
+            6 + (x |= 0)
+        );
+    }
+}
+
+evaluate_3: {
+    options = {
+        evaluate: true,
+        unsafe: true,
+        unsafe_math: true,
+    }
+    input: {
+        console.log(1 + Number(x) + 2);
+    }
+    expect: {
+        console.log(3 + +x);
+    }
+}
+
+evaluate_4: {
+    options = {
+        evaluate: true,
+    }
+    input: {
+        console.log(
+            1+ +a,
+            +a+1,
+            1+-a,
+            -a+1,
+            +a+ +b,
+            +a+-b,
+            -a+ +b,
+            -a+-b
+        );
+    }
+    expect: {
+        console.log(
+            +a+1,
+            +a+1,
+            1-a,
+            1-a,
+            +a+ +b,
+            +a-b,
+            -a+ +b,
+            -a-b
+        );
+    }
+}