[Wasm] Fix stdlib String to Float parse

libraries/stdlib/test/text/StringNumberConversionTest.kt

@@ -154,6 +154,27 @@ class StringNumberConversionTest {
         }
     }
 
+    @Test fun toFloat() {
+        compareConversion(String::toFloat, String::toFloatOrNull, ::floatTotalOrderEquals) {
+            assertProduces("-77", -77.0f)
+            assertProduces("77.", 77.0f)
+            assertProduces("77.0", 77.0f)
+            assertProduces("-1.77", -1.77f)
+            assertProduces("+.77", 0.77f)
+            assertProduces("\t-77 \n", -77.0f)
+            assertProduces("7.7e1", 77.0f)
+            assertProduces("+770e-1", 77.0f)
+
+            assertProduces("-NaN", -Float.NaN)
+            assertProduces("+Infinity", Float.POSITIVE_INFINITY)
+
+            assertFailsOrNull("7..7")
+            assertFailsOrNull("007 not a number")
+            assertFailsOrNull("")
+            assertFailsOrNull("   ")
+        }
+    }
+
 
 
     @Test fun toUByte() {
@@ -408,6 +429,8 @@ class StringNumberConversionTest {
 
 internal fun doubleTotalOrderEquals(a: Double?, b: Double?): Boolean = (a as Any?) == b
 
+internal fun floatTotalOrderEquals(a: Float?, b: Float?): Boolean = (a as Any?) == b
+
 internal fun <T : Any> compareConversion(
     convertOrFail: (String) -> T,
     convertOrNull: (String) -> T?,

libraries/stdlib/wasm/src/kotlin/text/StringNumberConversionsWasm.kt

@@ -6,7 +6,7 @@
 package kotlin.text
 
 import kotlin.math.abs
-
+import kotlin.wasm.internal.wasm_f32_demote_f64
 /**
  * Returns `true` if the content of this string is equal to the word "true", ignoring case, and `false` otherwise.
  */
@@ -84,13 +84,13 @@ public actual fun String.toDouble(): Double = kotlin.text.parseDouble(this)
  * Parses the string as a [Float] number and returns the result.
  * @throws NumberFormatException if the string is not a valid representation of a number.
  */
-public actual fun String.toFloat(): Float = toDouble() as Float
+public actual fun String.toFloat(): Float = wasm_f32_demote_f64(toDouble())
 
 /**
  * Parses the string as a [Float] number and returns the result
  * or `null` if the string is not a valid representation of a number.
  */
-public actual fun String.toFloatOrNull(): Float? = toDoubleOrNull() as Float?
+public actual fun String.toFloatOrNull(): Float? = toDoubleOrNull()?.let { wasm_f32_demote_f64(it) }
 
 /**
  * Parses the string as a [Double] number and returns the result