Use write!-style syntax for MIR assert terminator

[robojumper]

Fixes#71000.

r? @jonas-schievink

[rust-highfive]

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[robojumper]

The Debug implementation (#71000 (comment)) could not be changed as it is used for user-facing errors as well (via

rust/src/librustc_middle/mir/interpret/error.rs

Lines 540 to 558 in f363450

	impl fmt::DisplayforInterpError<'_>{
	fnfmt(&self,f:&mut fmt::Formatter<'_>) -> fmt::Result{
	// Forward `Display` to `Debug`.
	fmt::Debug::fmt(self, f)
	}
	}
	impl fmt::DebugforInterpError<'_>{
	fnfmt(&self,f:&mut fmt::Formatter<'_>) -> fmt::Result{
	useInterpError::*;
	match*self{
	Unsupported(ref msg) => write!(f,"{:?}", msg),
	InvalidProgram(ref msg) => write!(f,"{:?}", msg),
	UndefinedBehavior(ref msg) => write!(f,"{:?}", msg),
	ResourceExhaustion(ref msg) => write!(f,"{:?}", msg),
	MachineStop(ref msg) => write!(f,"{:?}", msg),
	}
	}
	}

)

[jonas-schievink]

Thanks, looks good!

@bors r+

[bors]

📌 Commit b78ff99 has been approved by jonas-schievink