tweak warning message for when tspan isn't an enclosing interval

src/bracketing/bisection.jl

@@ -40,7 +40,7 @@ function SciMLBase.solve(prob::IntervalNonlinearProblem, alg::Bisection,
     end
 
     if sign(fl) == sign(fr)
-        @warn "The interval is not an enclosing interval, opposite signs at the boundaries are required."
+        @warn "The interval is not an enclosing interval (does not contain a root). Returning boundary value."
         return build_solution(
             prob, alg, left, fl; retcode = ReturnCode.InitialFailure, left, right)
     end

src/bracketing/brent.jl

@@ -27,7 +27,7 @@ function SciMLBase.solve(prob::IntervalNonlinearProblem, alg::Brent, args...;
     end
 
     if sign(fl) == sign(fr)
-        @warn "The interval is not an enclosing interval, opposite signs at the boundaries are required."
+        @warn "The interval is not an enclosing interval (does not contain a root). Returning boundary value."
         return build_solution(
             prob, alg, left, fl; retcode = ReturnCode.InitialFailure, left, right)
     end

src/bracketing/falsi.jl

@@ -26,7 +26,7 @@ function SciMLBase.solve(prob::IntervalNonlinearProblem, alg::Falsi, args...;
     end
 
     if sign(fl) == sign(fr)
-        @warn "The interval is not an enclosing interval, opposite signs at the boundaries are required."
+        @warn "The interval is not an enclosing interval (does not contain a root). Returning boundary value."
         return build_solution(
             prob, alg, left, fl; retcode = ReturnCode.InitialFailure, left, right)
     end

src/bracketing/itp.jl

@@ -77,7 +77,7 @@ function SciMLBase.solve(prob::IntervalNonlinearProblem, alg::ITP, args...;
     end
 
     if sign(fl) == sign(fr)
-        @warn "The interval is not an enclosing interval, opposite signs at the boundaries are required."
+        @warn "The interval is not an enclosing interval (does not contain a root). Returning boundary value."
         return build_solution(
             prob, alg, left, fl; retcode = ReturnCode.InitialFailure, left, right)
     end

src/bracketing/ridder.jl

@@ -26,7 +26,7 @@ function SciMLBase.solve(prob::IntervalNonlinearProblem, alg::Ridder, args...;
     end
 
     if sign(fl) == sign(fr)
-        @warn "The interval is not an enclosing interval, opposite signs at the boundaries are required."
+        @warn "The interval is not an enclosing interval (does not contain a root). Returning boundary value."
         return build_solution(
             prob, alg, left, fl; retcode = ReturnCode.InitialFailure, left, right)
     end