1 files changed, 140 insertions, 0 deletions
diff --git a/library/core/tests/num/dec2flt/mod.rs b/library/core/tests/num/dec2flt/mod.rs
new file mode 100644
index 000000000..c4e105cba
--- /dev/null
+++ b/library/core/tests/num/dec2flt/mod.rs
@@ -0,0 +1,140 @@
+#![allow(overflowing_literals)]
+
+mod float;
+mod lemire;
+mod parse;
+
+// Take a float literal, turn it into a string in various ways (that are all trusted
+// to be correct) and see if those strings are parsed back to the value of the literal.
+// Requires a *polymorphic literal*, i.e., one that can serve as f64 as well as f32.
+macro_rules! test_literal {
+    ($x: expr) => {{
+        let x32: f32 = $x;
+        let x64: f64 = $x;
+        let inputs = &[stringify!($x).into(), format!("{:?}", x64), format!("{:e}", x64)];
+        for input in inputs {
+            assert_eq!(input.parse(), Ok(x64));
+            assert_eq!(input.parse(), Ok(x32));
+            let neg_input = &format!("-{input}");
+            assert_eq!(neg_input.parse(), Ok(-x64));
+            assert_eq!(neg_input.parse(), Ok(-x32));
+        }
+    }};
+}
+
+#[test]
+fn ordinary() {
+    test_literal!(1.0);
+    test_literal!(3e-5);
+    test_literal!(0.1);
+    test_literal!(12345.);
+    test_literal!(0.9999999);
+    test_literal!(2.2250738585072014e-308);
+}
+
+#[test]
+fn special_code_paths() {
+    test_literal!(36893488147419103229.0); // 2^65 - 3, triggers half-to-even with even significand
+    test_literal!(101e-33); // Triggers the tricky underflow case in AlgorithmM (for f32)
+    test_literal!(1e23); // Triggers AlgorithmR
+    test_literal!(2075e23); // Triggers another path through AlgorithmR
+    test_literal!(8713e-23); // ... and yet another.
+}
+
+#[test]
+fn large() {
+    test_literal!(1e300);
+    test_literal!(123456789.34567e250);
+    test_literal!(943794359898089732078308743689303290943794359843568973207830874368930329.);
+}
+
+#[test]
+fn subnormals() {
+    test_literal!(5e-324);
+    test_literal!(91e-324);
+    test_literal!(1e-322);
+    test_literal!(13245643e-320);
+    test_literal!(2.22507385851e-308);
+    test_literal!(2.1e-308);
+    test_literal!(4.9406564584124654e-324);
+}
+
+#[test]
+fn infinity() {
+    test_literal!(1e400);
+    test_literal!(1e309);
+    test_literal!(2e308);
+    test_literal!(1.7976931348624e308);
+}
+
+#[test]
+fn zero() {
+    test_literal!(0.0);
+    test_literal!(1e-325);
+    test_literal!(1e-326);
+    test_literal!(1e-500);
+}
+
+#[test]
+fn fast_path_correct() {
+    // This number triggers the fast path and is handled incorrectly when compiling on
+    // x86 without SSE2 (i.e., using the x87 FPU stack).
+    test_literal!(1.448997445238699);
+}
+
+#[test]
+fn lonely_dot() {
+    assert!(".".parse::<f32>().is_err());
+    assert!(".".parse::<f64>().is_err());
+}
+
+#[test]
+fn exponentiated_dot() {
+    assert!(".e0".parse::<f32>().is_err());
+    assert!(".e0".parse::<f64>().is_err());
+}
+
+#[test]
+fn lonely_sign() {
+    assert!("+".parse::<f32>().is_err());
+    assert!("-".parse::<f64>().is_err());
+}
+
+#[test]
+fn whitespace() {
+    assert!(" 1.0".parse::<f32>().is_err());
+    assert!("1.0 ".parse::<f64>().is_err());
+}
+
+#[test]
+fn nan() {
+    assert!("NaN".parse::<f32>().unwrap().is_nan());
+    assert!("NaN".parse::<f64>().unwrap().is_nan());
+}
+
+#[test]
+fn inf() {
+    assert_eq!("inf".parse(), Ok(f64::INFINITY));
+    assert_eq!("-inf".parse(), Ok(f64::NEG_INFINITY));
+    assert_eq!("inf".parse(), Ok(f32::INFINITY));
+    assert_eq!("-inf".parse(), Ok(f32::NEG_INFINITY));
+}
+
+#[test]
+fn massive_exponent() {
+    let max = i64::MAX;
+    assert_eq!(format!("1e{max}000").parse(), Ok(f64::INFINITY));
+    assert_eq!(format!("1e-{max}000").parse(), Ok(0.0));
+    assert_eq!(format!("1e{max}000").parse(), Ok(f64::INFINITY));
+}
+
+#[test]
+fn borderline_overflow() {
+    let mut s = "0.".to_string();
+    for _ in 0..375 {
+        s.push('3');
+    }
+    // At the time of this writing, this returns Err(..), but this is a bug that should be fixed.
+    // It makes no sense to enshrine that in a test, the important part is that it doesn't panic.
+    let _ = s.parse::<f64>();
+}