### Terraform Version ```shell Terraform v1.15.6 on darwin_arm64 ``` ### Terraform Configuration Files No Terraform configuration is required. The issue reproduces directly in `terraform console` with ordinary scalar expressions: ```terraform log(-1, 10) log(1, 1) pow(-2, 0.5) ``` ### Debug Output A separate `TF_LOG` debug log is not needed to reproduce this. The console output itself includes the internal panic and stack trace. Excerpt: ```text Call to function "log" failed: panic in function implementation: Float.SetFloat64(NaN) ... github.com/zclconf/go-cty/cty.NumberFloatVal(...) ``` `pow(-2, 0.5)` fails the same way, through `Float.SetFloat64(NaN)`. ### Expected Behavior Terraform should return a normal function-call diagnostic for inputs whose mathematical result is undefined / NaN, rather than exposing an internal panic and Go stack trace to the user. ### Actual Behavior `log()` and `pow()` can produce `NaN` for validly-typed scalar inputs. That `NaN` is then passed to `cty.NumberFloatVal`, which is backed by `big.Float` and panics on `Float.SetFloat64(NaN)`. The panic is surfaced to the user as: ```text panic in function implementation: Float.SetFloat64(NaN) ``` followed by a full stack trace. Examples: - `log(-1, 10)` - logarithm of a negative number - `log(1, 1)` - base 1 gives `0/0` - `pow(-2, 0.5)` - negative base raised to a fractional power ### Steps to Reproduce 1. Run `printf "log(-1, 10)\n" | terraform console` 2. Run `printf "log(1, 1)\n" | terraform console` 3. Run `printf "pow(-2, 0.5)\n" | terraform console` ### Additional Context This is not tied to providers or external services. It is a Terraform language function behavior. Go `math.Log` / `math.Pow` return `NaN` for these cases, and `cty.NumberFloatVal` cannot accept `NaN`. ### References - #38883