Auto merge of #31410 - rkruppe:issue31109, r=pnkfelix

Issue #31109 uncovered two semi-related problems:

* A panic in `str::parse::<f64>`
* A panic in `rustc::middle::const_eval::lit_to_const` where the result of float parsing was unwrapped.

This series of commits fixes both issues and also drive-by-fixes some things I noticed while tracking down the parsing panic.

Author: bors

src/etc/test-float-parse/_common.rs

@@ -16,7 +16,7 @@ use std::mem::transmute;
 #[allow(dead_code)]
 pub const SEED: [u32; 3] = [0x243f_6a88, 0x85a3_08d3, 0x1319_8a2e];
 
-pub fn validate(text: String) {
+pub fn validate(text: &str) {
     let mut out = io::stdout();
     let x: f64 = text.parse().unwrap();
     let f64_bytes: u64 = unsafe { transmute(x) };

src/etc/test-float-parse/few-ones.rs

@@ -20,7 +20,7 @@ fn main() {
     for a in &pow {
         for b in &pow {
             for c in &pow {
-                validate((a | b | c).to_string());
+                validate(&(a | b | c).to_string());
             }
         }
     }

src/etc/test-float-parse/huge-pow10.rs

@@ -15,7 +15,7 @@ use _common::validate;
 fn main() {
     for e in 300..310 {
         for i in 0..100000 {
-            validate(format!("{}e{}", i, e));
+            validate(&format!("{}e{}", i, e));
         }
     }
 }

src/etc/test-float-parse/long-fractions.rs

@@ -0,0 +1,27 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+mod _common;
+
+use std::char;
+use _common::validate;
+
+fn main() {
+    for n in 0..10 {
+        let digit = char::from_digit(n, 10).unwrap();
+        let mut s = "0.".to_string();
+        for _ in 0..400 {
+            s.push(digit);
+            if s.parse::<f64>().is_ok() {
+                validate(&s);
+            }
+        }
+    }
+}

src/etc/test-float-parse/many-digits.rs

@@ -23,9 +23,9 @@ fn main() {
     let mut rnd = IsaacRng::from_seed(&SEED);
     let mut range = Range::new(0, 10);
     for _ in 0..5_000_000u64 {
-        let num_digits = rnd.gen_range(100, 300);
+        let num_digits = rnd.gen_range(100, 400);
         let digits = gen_digits(num_digits, &mut range, &mut rnd);
-        validate(digits);
+        validate(&digits);
     }
 }
 

src/etc/test-float-parse/rand-f64.rs

@@ -25,7 +25,7 @@ fn main() {
         let bits = rnd.next_u64();
         let x: f64 = unsafe { transmute(bits) };
         if x.is_finite() {
-            validate(format!("{:e}", x));
+            validate(&format!("{:e}", x));
             i += 1;
         }
     }

src/etc/test-float-parse/runtests.py

@@ -21,8 +21,9 @@
 
 The actual tests (generating decimal strings and feeding them to dec2flt) is
 performed by a set of stand-along rust programs. This script compiles, runs,
-and supervises them. In particular, the programs report the strings they
-generate and the floating point numbers they converted those strings to.
+and supervises them. The programs report the strings they generate and the
+floating point numbers they converted those strings to, and this script
+checks that the results are correct.
 
 You can run specific tests rather than all of them by giving their names
 (without .rs extension) as command line parameters.
@@ -64,9 +65,9 @@
 exit code that's not 0, the test fails.
 The output on stdout is treated as (f64, f32, decimal) record, encoded thusly:
 
-- The first eight bytes are a binary64 (native endianness).
-- The following four bytes are a binary32 (native endianness).
-- Then the corresponding string input follows, in ASCII (no newline).
+- First, the bits of the f64 encoded as an ASCII hex string.
+- Second, the bits of the f32 encoded as an ASCII hex string.
+- Then the corresponding string input, in ASCII
 - The record is terminated with a newline.
 
 Incomplete records are an error. Not-a-Number bit patterns are invalid too.

src/etc/test-float-parse/short-decimals.rs

@@ -22,8 +22,8 @@ fn main() {
             if i % 10 == 0 {
                 continue;
             }
-            validate(format!("{}e{}", i, e));
-            validate(format!("{}e-{}", i, e));
+            validate(&format!("{}e{}", i, e));
+            validate(&format!("{}e-{}", i, e));
         }
     }
 }

src/etc/test-float-parse/subnorm.rs

@@ -16,8 +16,8 @@ use _common::validate;
 fn main() {
     for bits in 0u32..(1 << 21) {
         let single: f32 = unsafe { transmute(bits) };
-        validate(format!("{:e}", single));
+        validate(&format!("{:e}", single));
         let double: f64 = unsafe { transmute(bits as u64) };
-        validate(format!("{:e}", double));
+        validate(&format!("{:e}", double));
     }
 }

src/etc/test-float-parse/tiny-pow10.rs

@@ -15,7 +15,7 @@ use _common::validate;
 fn main() {
     for e in 301..327 {
         for i in 0..100000 {
-            validate(format!("{}e-{}", i, e));
+            validate(&format!("{}e-{}", i, e));
         }
     }
 }